Move the calls to memcpy_fromio() up into the loop in dmi_scan_machine(),
and move the signature checks back down into dmi_decode(). We need to
check at 16-byte intervals but keep a 32-byte buffer for an SMBIOS entry,
so shift the buffer after each iteration.
Merge smbios_present() into dmi_present(), so we look for an SMBIOS
signature at the beginning of the given buffer and then for a DMI
signature at an offset of 16 bytes.
Signed-off-by: Ben Hutchings <ben@decadent.org.uk> Reported-by: Tim McGrath <tmhikaru@gmail.com> Tested-by: Tim Mcgrath <tmhikaru@gmail.com> Cc: Zhenzhong Duan <zhenzhong.duan@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Steven Rostedt [Wed, 20 Mar 2013 04:07:49 +0000 (15:07 +1100)]
init: scream bloody murder if interrupts are enabled too early
As I was testing a lot of my code recently, and having several
"successes", I accidentally noticed in the dmesg this little line:
[ 0.000000] start_kernel(): bug: interrupts were enabled *very* early, fixing it
Sure enough, one of my patches two commits ago enabled interrupts early.
The sad part here is that I never noticed it, and I ran several tests with
ktest too, and ktest did not notice this line.
What ktest looks for (and so does many other automated testing scripts) is
a back trace produced by a WARN_ON() or BUG(). As a back trace was never
produced, my buggy patch could have slipped into linux-next, or even
worse, mainline.
Adding a WARN(!irqs_disabled()) makes this bug a little more obvious:
[ 0.000000] PID hash table entries: 4096 (order: 3, 32768 bytes)
[ 0.000000] __ex_table already sorted, skipping sort
[ 0.000000] Checking aperture...
[ 0.000000] No AGP bridge found
[ 0.000000] Calgary: detecting Calgary via BIOS EBDA area
[ 0.000000] Calgary: Unable to locate Rio Grande table in EBDA - bailing!
[ 0.000000] Memory: 2003252k/2054848k available (4857k kernel code, 460k absent, 51136k reserved, 6210k data, 1096k init)
[ 0.000000] ------------[ cut here ]------------
[ 0.000000] WARNING: at /home/rostedt/work/git/linux-trace.git/init/main.c:543 start_kernel+0x21e/0x415()
[ 0.000000] Hardware name: To Be Filled By O.E.M.
[ 0.000000] Interrupts were enabled *very* early, fixing it
[ 0.000000] Modules linked in:
[ 0.000000] Pid: 0, comm: swapper/0 Not tainted 3.8.0-test+ #286
[ 0.000000] Call Trace:
[ 0.000000] [<ffffffff81037b79>] warn_slowpath_common+0x83/0x9b
[ 0.000000] [<ffffffff81037c34>] warn_slowpath_fmt+0x46/0x48
[ 0.000000] [<ffffffff81ae4a39>] start_kernel+0x21e/0x415
[ 0.000000] [<ffffffff81ae4623>] ? repair_env_string+0x56/0x56
[ 0.000000] [<ffffffff81ae4312>] x86_64_start_reservations+0x10e/0x112
[ 0.000000] [<ffffffff81ae4120>] ? early_idt_handlers+0x120/0x120
[ 0.000000] [<ffffffff81ae4418>] x86_64_start_kernel+0x102/0x111
[ 0.000000] ---[ end trace 007d8b0491b4f5d8 ]---
[ 0.000000] Preemptible hierarchical RCU implementation.
[ 0.000000] RCU restricting CPUs from NR_CPUS=8 to nr_cpu_ids=4.
[ 0.000000] NR_IRQS:4352 nr_irqs:712 16
[ 0.000000] Console: colour VGA+ 80x25
[ 0.000000] console [ttyS0] enabled, bootconsole disabled
Do you see it?
The original version of this patch just slapped a WARN_ON() in there and
kept the printk(). Ard van Breemen suggested using the WARN() interface,
which makes the code a bit cleaner.
Also, while examining other warnings in init/main.c, I found two other
locations that deserve a bloody murder scream if their conditions are hit,
and updated them accordingly.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Cc: Ard van Breemen <ard@telegraafnet.nl> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
We observed this problem has been occurring since 2.6.30 with
fs/binfmt_elf.c: create_elf_tables()->get_random_bytes(), introduced by f06295b44c296c8f ("ELF: implement AT_RANDOM for glibc PRNG seeding").
/*
* Generate 16 random bytes for userspace PRNG seeding.
*/
get_random_bytes(k_rand_bytes, sizeof(k_rand_bytes));
The patch introduces a wrapper around get_random_int() which has lower
overhead than calling get_random_bytes() directly.
With this patch applied:
$ cat /proc/sys/kernel/random/entropy_avail
2731
$ cat /proc/sys/kernel/random/entropy_avail
2802
$ cat /proc/sys/kernel/random/entropy_avail
2878
Analyzed by John Sobecki.
Signed-off-by: Jie Liu <jeff.liu@oracle.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Andreas Dilger <aedilger@gmail.com> Cc: Alan Cox <alan@linux.intel.com> Cc: Arnd Bergmann <arnn@arndb.de> Cc: John Sobecki <john.sobecki@oracle.com> Cc: James Morris <james.l.morris@oracle.com> Cc: Jakub Jelinek <jakub@redhat.com> Cc: Ted Ts'o <tytso@mit.edu> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Acked-by: Kees Cook <keescook@chromium.org> Cc: Ulrich Drepper <drepper@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Eric Wong [Wed, 20 Mar 2013 04:07:48 +0000 (15:07 +1100)]
epoll: cleanup: hoist out f_op->poll calls
This reduces the amount of code inside the ready list iteration loops for
better readability IMHO.
Signed-off-by: Eric Wong <normalperson@yhbt.net> Cc: Davide Libenzi <davidel@xmailserver.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Eric Wong [Wed, 20 Mar 2013 04:07:48 +0000 (15:07 +1100)]
epoll: lock ep->mtx in ep_free to silence lockdep
Technically we do not need to hold ep->mtx during ep_free since we are
certain there are no other users of ep at that point. However, lockdep
complains with a "suspicious rcu_dereference_check() usage!" message; so
lock the mutex before ep_remove to silence the warning.
Signed-off-by: Eric Wong <normalperson@yhbt.net> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Arve Hjønnevåg <arve@android.com> Cc: Davide Libenzi <davidel@xmailserver.org> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: NeilBrown <neilb@suse.de>, Cc: Rafael J. Wysocki <rjw@sisk.pl> Cc: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Paton J. Lewis [Wed, 20 Mar 2013 04:07:47 +0000 (15:07 +1100)]
epoll: support for disabling items, and a self-test app
It is not currently possible to reliably delete epoll items when using the
same epoll set from multiple threads. After calling epoll_ctl with
EPOLL_CTL_DEL, another thread might still be executing code related to an
event for that epoll item (in response to epoll_wait). Therefore the
deleting thread does not know when it is safe to delete resources
pertaining to the associated epoll item because another thread might be
using those resources.
The deleting thread could wait an arbitrary amount of time after calling
epoll_ctl with EPOLL_CTL_DEL and before deleting the item, but this is
inefficient and could result in the destruction of resources before
another thread is done handling an event returned by epoll_wait.
This patch enhances epoll_ctl to support EPOLL_CTL_DISABLE, which disables
an epoll item. If epoll_ctl returns -EBUSY in this case, then another
thread may handling a return from epoll_wait for this item. Otherwise if
epoll_ctl returns 0, then it is safe to delete the epoll item. This
allows multiple threads to use a mutex to determine when it is safe to
delete an epoll item and its associated resources, which allows epoll
items to be deleted both efficiently and without error in a multi-threaded
environment. Note that EPOLL_CTL_DISABLE is only useful in conjunction
with EPOLLONESHOT, and using EPOLL_CTL_DISABLE on an epoll item without
EPOLLONESHOT returns -EINVAL.
This patch also adds a new test_epoll self-test program to both
demonstrate the need for this feature and test it.
Signed-off-by: Paton J. Lewis <palewis@adobe.com> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: Jason Baron <jbaron@redhat.com> Cc: Paul Holland <pholland@adobe.com> Cc: Davide Libenzi <davidel@xmailserver.org> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Eric Wong [Wed, 20 Mar 2013 04:07:47 +0000 (15:07 +1100)]
epoll: comment + BUILD_BUG_ON to prevent epitem bloat
This will prevent us from accidentally introducing a memory bloat
regression here in the future.
Signed-off-by: Eric Wong <normalperson@yhbt.net> Cc: Davide Libenzi <davidel@xmailserver.org>, Cc: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Andrew Morton [Wed, 20 Mar 2013 04:07:47 +0000 (15:07 +1100)]
epoll-trim-epitem-by-one-cache-line-on-x86_64-fix
use __packed, for all architectures
Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: Davide Libenzi <davidel@xmailserver.org> Cc: Eric Wong <normalperson@yhbt.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Eric Wong [Wed, 20 Mar 2013 04:07:46 +0000 (15:07 +1100)]
epoll: trim epitem by one cache line
It is common for epoll users to have thousands of epitems, so saving a
cache line on every allocation leads to large memory savings.
Since epitem allocations are cache-aligned, reducing sizeof(struct epitem)
from 136 bytes to 128 bytes will allow it to squeeze under a cache line
boundary on x86_64.
Via /sys/kernel/slab/eventpoll_epi, I see the following changes on my
x86_64 Core2 Duo (which has 64-byte cache alignment):
object_size : 192 => 128
objs_per_slab: 21 => 32
Also, add a BUILD_BUG_ON() to check for future accidental breakage.
Signed-off-by: Eric Wong <normalperson@yhbt.net> Cc: Davide Libenzi <davidel@xmailserver.org> Cc: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Joe Perches [Wed, 20 Mar 2013 04:07:45 +0000 (15:07 +1100)]
checkpatch: add check for reuse of krealloc arg
On Thu, 2013-03-14 at 13:30 +0000, David Woodhouse wrote:
> If krealloc() returns NULL, it *doesn't* free the original. So any code
> of the form 'foo = krealloc(foo, …);' is almost certainly a bug.
So add a check for it to checkpatch.
Signed-off-by: Joe Perches <joe@perches.com> Tested-by: Guenter Roeck <linux@roeck-us.net> Acked-by: Guenter Roeck <linux@roeck-us.net> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Andy Whitcroft <apw@canonical.com> Cc: Jean Delvare <khali@linux-fr.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Oleg Nesterov [Wed, 20 Mar 2013 04:07:45 +0000 (15:07 +1100)]
argv_split(): teach it to handle mutable strings
argv_split() allocates argv[count_argc(str)] array and assumes that it
will find the same number of arguments later. This is obviously wrong if
this string can be changed, say, by sysctl.
With this patch argv_split() kstrndup's the whole string and does not
split it, we simply replace the spaces with zeroes and keep the allocated
memory in argv[-1] for argv_free(arg).
We do not use argv[0] because:
- str can be all-spaces or empty. In fact this case is fine,
we could kfree() it before return, but:
- str can have a space at the start, and we can not rely on
kstrndup(skip_spaces(str)) because it can equally race if
this string is mutable.
Also, simplify count_argc() and kill the no longer used skip_arg().
drivers/leds/leds-ot200.c: fix error caused by shifted mask
During the development of this driver an in-house register documentation
was used. The last week some integration tests were done and this problem
was found. It turned out that the released register documentation is
wrong.
The fix is very simple: shift all masks by one.
Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com> Cc: Bryan Wu <cooloney@gmail.com> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Stefano Babic [Wed, 20 Mar 2013 04:07:43 +0000 (15:07 +1100)]
video: backlight: add ili922x lcd driver
Add LCD driver for Ilitek ILI9221/ILI9222 controller. The driver uses SPI
interface for controller access and configuration and RGB interface for
graphics data transfer.
Signed-off-by: Stefano Babic <sbabic@denx.de> Signed-off-by: Anatolij Gustschin <agust@denx.de> Cc: Richard Purdie <rpurdie@rpsys.net> Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de> Cc: Jingoo Han <jg1.han@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Devendra Naga [Wed, 20 Mar 2013 04:07:43 +0000 (15:07 +1100)]
drivers/video/backlight/adp5520_bl.c: fix compiler warning in adp5520_show()
While compiling with make W=1 (gcc gcc (GCC) 4.7.2 20121109 (Red Hat
4.7.2-8)) found the following warning
drivers/video/backlight/adp5520_bl.c: In function `adp5520_show':
drivers/video/backlight/adp5520_bl.c:146:6: warning: variable `error' set but not used [-Wunused-but-set-variable]
fixed by checking the return value of the variable
Signed-off-by: Devendra Naga <devendra.aaru@gmail.com> Acked-by: Jingoo Han <jg1.han@samsung.com> Cc: Michael Hennerich <michael.hennerich@analog.com> Cc: Richard Purdie <rpurdie@rpsys.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Paul Bolle [Wed, 20 Mar 2013 04:07:43 +0000 (15:07 +1100)]
drivers/video/backlight/Kconfig: fix typo "MACH_SAM9...EK" three times
Fix three typos (originally) introduced by a9a84c37d ("atmel_lcdfb:
backlight control").
Two of these typos were introduced in v2.6.25. (The third was introduced
in 915190f7d4f08 ("[ARM] 5614/1: at91: atmel_lcdfb: add at91sam9g10
support to atmel LCD driver")). Checking these commits reveals that the
default value of 'y' has never been set automatically in all releases
since v2.6.25! Perhaps this line might as well be dropped.
Signed-off-by: Paul Bolle <pebolle@tiscali.nl> Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de> Acked-by: Jingoo Han <jg1.han@samsung.com> Cc: Nicolas Ferre <nicolas.ferre@atmel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Jingoo Han [Wed, 20 Mar 2013 04:07:38 +0000 (15:07 +1100)]
drivers/video/backlight/l4f00242t03.c: check return value of regulator_enable()
regulator_enable() is marked as as __must_check. Therefore the return
value of regulator_enable() should be checked. Also, this patch checks
return value of regulator_set_voltage().
Signed-off-by: Jingoo Han <jg1.han@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Add missing braces to include error message. The error message is related
to the return value for sysfs_create_group(). However,
sysfs_create_group() is called when pdata->en_ambl_sens is not zero.
Thus, the checking return value should be included in the if statement.
Signed-off-by: Jingoo Han <jg1.han@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Devendra Naga [Wed, 20 Mar 2013 04:07:37 +0000 (15:07 +1100)]
drivers/video/backlight/lp855x_bl.c: fix compiler warning in lp855x_probe
while doing with make W=1 gcc (gcc (GCC) 4.7.2 20121109 (Red Hat 4.7.2-8))
found
drivers/video/backlight/lp855x_bl.c: In function `lp855x_probe':
drivers/video/backlight/lp855x_bl.c:342:35: warning: variable `mode' set but not used [-Wunused-but-set-variable]
fixed by removing it as since its not used anywhere
Signed-off-by: Devendra Naga <devendra.aaru@gmail.com> Acked-by: Milo Kim <milo.kim@ti.com> Cc: Jingoo Han <jg1.han@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When the macro such as SIMPLE_DEV_PM_OPS is used, there is no need to use
'#ifdef CONFIG_PM' to prevent build error. Thus, this patch removes
unnecessary ifdefs.
Signed-off-by: Jingoo Han <jg1.han@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Joe Perches <joe@perches.com> Cc: Marcin Slusarz <marcin.slusarz@gmail.com> Cc: Stephen Warren <swarren@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Stephen Warren [Wed, 20 Mar 2013 04:07:34 +0000 (15:07 +1100)]
get_maintainer: use filename-only regex match for Tegra
Create a new N: entry type in MAINTAINERS which performs a regex match
against filenames; either those extracted from patch +++ or --- lines, or
those specified on the command-line using the -f option.
This provides the same benefits as using a K: regex option to match a set
of filenames (see commit eb90d08 "get_maintainer: allow keywords to match
filenames"), but without the disadvantage that "random" file content, such
as comments, will ever match the regex. Hence, revert most of that
commit.
Switch the Tegra entry from using K: to N:
Reported-by: Marcin Slusarz <marcin.slusarz@gmail.com> Suggested-by: Joe Perches <joe@perches.com> Signed-off-by: Stephen Warren <swarren@nvidia.com> Acked-by: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Andrew Morton [Wed, 20 Mar 2013 04:07:34 +0000 (15:07 +1100)]
include/linux/printk.h: include stdarg.h
printk.h uses va_list but doesn't include stdarg.h. Hence printk.h is
unusable unless its includer has already included kernel.h (which includes
stdarg.h).
Remove the dependency by including stdarg.h in printk.h
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Thomas Gleixner [Wed, 20 Mar 2013 04:07:33 +0000 (15:07 +1100)]
early_printk: consolidate random copies of identical code
The early console implementations are the same all over the place. Move
the print function to kernel/printk and get rid of the copies.
[v3: drop sparc bits as suggested by tglx, redo build tests on sparc
sparc32, Randy's randconfig, ppc, mips, arm...]
[v2: essentially unchanged since v1, so I've left the acked/reviewed
tags. There was a compile fail[1] for a randconfig with EARLY_PRINTK=y
and PRINTK=n, because the early_console struct and early_printk calls
were nested within an #ifdef CONFIG_PRINTK -- moving that whole block
exactly as-is to be outside the #ifdef CONFIG_PRINTK fixes the randconfig
and still works for everyday sane configs too.]
[1] http://marc.info/?l=linux-next&m=136219350914998&w=2
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Russell King <linux@arm.linux.org.uk> Acked-by: Mike Frysinger <vapier@gentoo.org> Cc: Michal Simek <monstr@monstr.eu> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mundt <lethal@linux-sh.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Richard Weinberger <richard@nod.at> Reviewed-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Thomas Gleixner [Wed, 20 Mar 2013 04:07:33 +0000 (15:07 +1100)]
early_printk: consolidate random copies of identical code
The early console implementations are the same all over the place. Move
the print function to kernel/printk and get rid of the copies.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Russell King <linux@arm.linux.org.uk> Acked-by: Mike Frysinger <vapier@gentoo.org> Cc: Michal Simek <monstr@monstr.eu> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mundt <lethal@linux-sh.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Richard Weinberger <richard@nod.at> Reviewed-by: Ingo Molnar <mingo@kernel.org> Tested-by: Paul Gortmaker <paul.gortmaker@windriver.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
zhangwei(Jovi) [Wed, 20 Mar 2013 04:07:33 +0000 (15:07 +1100)]
printk/tracing: rework console tracing
commit 7ff9554bb ("printk: convert byte-buffer to variable-length record
buffer") removed start and end parameters in call_console_drivers, but
those parameters still exists in include/trace/events/printk.h.
Without start and end parameters handling, printk tracing became more
simple as: trace_console(text, len);
Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com> Acked-by: Steven Rostedt <rostedt@goodmis.org> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Kay Sievers <kay@vrfy.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Fan Du [Wed, 20 Mar 2013 04:07:32 +0000 (15:07 +1100)]
include/linux/fs.h: disable preempt when acquire i_size_seqcount write lock
Two rt tasks bind to one CPU core.
The higher priority rt task A preempts a lower priority rt task B which
has already taken the write seq lock, and then the higher priority rt task
A try to acquire read seq lock, it's doomed to lockup.
rt task A with lower priority: call write
i_size_write rt task B with higher priority: call sync, and preempt task A
write_seqcount_begin(&inode->i_size_seqcount); i_size_read
inode->i_size = i_size; read_seqcount_begin <-- lockup here...
So disable preempt when acquiring every i_size_seqcount *write* lock will
cure the problem.
Signed-off-by: Fan Du <fan.du@windriver.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Chuansheng Liu [Wed, 20 Mar 2013 04:07:32 +0000 (15:07 +1100)]
smp: Give WARN()ing when calling smp_call_function_many()/single() in serving irq
Currently the functions smp_call_function_many()/single() will give a
WARN()ing only in the case of irqs_disabled(), but that check is not
enough to guarantee execution of the SMP cross-calls.
In many other cases such as softirq handling/interrupt handling, the two
APIs still can not be called, just as the smp_call_function_many()
comments say:
* You must not call this function with disabled interrupts or from a
* hardware interrupt handler or from a bottom half handler. Preemption
* must be disabled when calling this function.
There is a real case for softirq DEADLOCK case:
CPUA CPUB
spin_lock(&spinlock)
Any irq coming, call the irq handler
irq_exit()
spin_lock_irq(&spinlock)
<== Blocking here due to
CPUB hold it
__do_softirq()
run_timer_softirq()
timer_cb()
call smp_call_function_many()
send IPI interrupt to CPUA
wait_csd()
Then both CPUA and CPUB will be deadlocked here.
So we should give a warning in the nmi, hardirq or softirq context as well.
Moreover, adding one new macro in_serving_irq() which indicates we are
processing nmi, hardirq or sofirq.
Signed-off-by: liu chuansheng <chuansheng.liu@intel.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Tested-by: Fengguang Wu <fengguang.wu@intel.com> Cc: Lai Jiangshan <eag0628@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
anish kumar [Wed, 20 Mar 2013 04:07:31 +0000 (15:07 +1100)]
kernel/watchdog.c: add comments to explain watchdog_disabled variable
This watchdog_disabled flag is a bit cryptic. However it's usefulness is
multifold. Uses are:
1. Check if smpboot_register_percpu_thread function passed.
2. Makes sure that user enables and disables the watchdog in sequence
i.e. enable watchdog->disable watchdog->enable watchdog
Unlike enable watchdog->enable watchdog which is wrong.
[dzickus@redhat.com: small text cleanups] Signed-off-by: anish kumar <anish198519851985@gmail.com> Signed-off-by: Don Zickus <dzickus@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Glauber Costa [Wed, 20 Mar 2013 04:07:30 +0000 (15:07 +1100)]
memcg: debugging facility to access dangling memcgs
If memcg is tracking anything other than plain user memory (swap, tcp buf
mem, or slab memory), it is possible - and normal - that a reference will
be held by the group after it is dead. Still, for developers, it would be
extremely useful to be able to query about those states during debugging.
This patch provides a debugging facility in the root memcg, so we can
inspect which memcgs still have pending objects, and what is the cause of
this state.
Signed-off-by: Glauber Costa <glommer@parallels.com> Acked-by: Michal Hocko <mhocko@suse.cz> Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Xi Wang [Wed, 20 Mar 2013 04:07:30 +0000 (15:07 +1100)]
mm/dmapool.c: fix null dev in dma_pool_create()
A few drivers invoke dma_pool_create() with a null dev. Note that dev is
dereferenced in dev_to_node(dev), causing a null pointer dereference.
A long term solution is to disallow null dev. Once the drivers are fixed,
we can simplify the core code here. For now we add WARN_ON(!dev) to
notify the driver maintainers and avoid the null pointer dereference.
Signed-off-by: Xi Wang <xi.wang@gmail.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Xi Wang [Wed, 20 Mar 2013 04:07:30 +0000 (15:07 +1100)]
drivers/usb/gadget/amd5536udc.c: avoid calling dma_pool_create() with NULL dev
Calling dma_pool_create() with dev==NULL will oops on a NUMA machine.
Rather than changing dma_pool_create() we wish to disallow passing
dev==NULL. This requires fixing up the small number of drivers which are
passing in dev==NULL.
Use &dev->pdev->dev instead of NULL.
Signed-off-by: Xi Wang <xi.wang@gmail.com> Cc: Felipe Balbi <balbi@ti.com> Cc: Greg KH <greg@kroah.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Michal Hocko [Wed, 20 Mar 2013 04:07:29 +0000 (15:07 +1100)]
drop_caches: add some documentation and info message
I would like to resurrect Dave's patch. The last time it was posted was
here https://lkml.org/lkml/2010/9/16/250 and there didn't seem to be any
strong opposition.
Kosaki was worried about possible excessive logging when somebody drops
caches too often (but then he claimed he didn't have a strong opinion on
that) but I would say opposite. If somebody does that then I would really
like to know that from the log when supporting a system because it almost
for sure means that there is something fishy going on. It is also worth
mentioning that only root can write drop caches so this is not an flooding
attack vector.
I am bringing that up again because this can be really helpful when
chasing strange performance issues which (surprise surprise) turn out to
be related to artificially dropped caches done because the admin thinks
this would help...
I have just refreshed the original patch on top of the current mm tree
but I could live with KERN_INFO as well if people think that KERN_NOTICE
is too hysterical.
: From: Dave Hansen <dave@linux.vnet.ibm.com>
: Date: Fri, 12 Oct 2012 14:30:54 +0200
:
: There is plenty of anecdotal evidence and a load of blog posts
: suggesting that using "drop_caches" periodically keeps your system
: running in "tip top shape". Perhaps adding some kernel
: documentation will increase the amount of accurate data on its use.
:
: If we are not shrinking caches effectively, then we have real bugs.
: Using drop_caches will simply mask the bugs and make them harder
: to find, but certainly does not fix them, nor is it an appropriate
: "workaround" to limit the size of the caches.
:
: It's a great debugging tool, and is really handy for doing things
: like repeatable benchmark runs. So, add a bit more documentation
: about it, and add a little KERN_NOTICE. It should help developers
: who are chasing down reclaim-related bugs.
[mhocko@suse.cz: refreshed to current -mm tree]
[akpm@linux-foundation.org: checkpatch fixes] Signed-off-by: Dave Hansen <dave@linux.vnet.ibm.com> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Michal Hocko <mhocko@suse.cz> Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Mike Yoknis [Wed, 20 Mar 2013 04:07:29 +0000 (15:07 +1100)]
mm: memmap_init_zone() performance improvement
We have what we call an "architectural simulator". It is a computer
program that pretends that it is a computer system. We use it to test the
firmware before real hardware is available. We have booted Linux on our
simulator. As you would expect it takes longer to boot on the simulator
than it does on real hardware.
With my patch - boot time 41 minutes
Without patch - boot time 94 minutes
These numbers do not scale linearly to real hardware. But indicate to me
a place where Linux can be improved.
memmap_init_zone() loops through every Page Frame Number (pfn), including
pfn values that are within the gaps between existing memory sections. The
unneeded looping will become a boot performance issue when machines
configure larger memory ranges that will contain larger and more numerous
gaps.
The code will skip across invalid pfn values to reduce the number of loops
executed.
Signed-off-by: Mike Yoknis <mike.yoknis@hp.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Catalin Marinas [Wed, 20 Mar 2013 04:07:28 +0000 (15:07 +1100)]
arm: set the page table freeing ceiling to TASK_SIZE
ARM processors with LPAE enabled use 3 levels of page tables, with an
entry in the top level (pgd) covering 1GB of virtual space. Because of
the branch relocation limitations on ARM, the loadable modules are mapped
16MB below PAGE_OFFSET, making the corresponding 1GB pgd shared between
kernel modules and user space.
If free_pgtables() is called with the default ceiling 0, free_pgd_range()
(and subsequently called functions) also frees the page table shared
between user space and kernel modules (which is normally handled by the
ARM-specific pgd_free() function). This patch changes defines the ARM
USER_PGTABLES_CEILING to TASK_SIZE when CONFIG_ARM_LPAE is enabled.
Note that the pgd_free() function already checks the presence of the
shared pmd page allocated by pgd_alloc() and frees it, though with ceiling
0 this wasn't necessary.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Russell King <linux@arm.linux.org.uk> Cc: Hugh Dickins <hughd@google.com> Cc: <stable@vger.kernel.org> [3.3+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Hugh Dickins [Wed, 20 Mar 2013 04:07:28 +0000 (15:07 +1100)]
mm: allow arch code to control the user page table ceiling
On architectures where a pgd entry may be shared between user and kernel
(e.g. ARM+LPAE), freeing page tables needs a ceiling other than 0. This
patch introduces a generic USER_PGTABLES_CEILING that arch code can
override. It is the responsibility of the arch code setting the ceiling
to ensure the complete freeing of the page tables (usually in pgd_free()).
[catalin.marinas@arm.com: commit log; shift_arg_pages(), asm-generic/pgtables.h changes] Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Russell King <linux@arm.linux.org.uk> Cc: <stable@vger.kernel.org> [3.3+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Michal Hocko [Wed, 20 Mar 2013 04:07:27 +0000 (15:07 +1100)]
memcg: do not check for do_swap_account in mem_cgroup_{read,write,reset}
Since 2d11085e ("memcg: do not create memsw files if swap accounting is
disabled") memsw files are created only if memcg swap accounting is
enabled so it doesn't make any sense to check for it explicitly in
mem_cgroup_read(), mem_cgroup_write() and mem_cgroup_reset().
Signed-off-by: Michal Hocko <mhocko@suse.cz> Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Tejun Heo <tj@kernel.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Zhang Yanfei [Wed, 20 Mar 2013 04:07:27 +0000 (15:07 +1100)]
mmap: find_vma: remove the WARN_ON_ONCE(!mm) check
Remove the WARN_ON_ONCE(!mm) check as the comment suggested. Kernel code
calls find_vma only when it is absolutely sure that the mm_struct arg to
it is non-NULL.
Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Atsushi Kumagai [Wed, 20 Mar 2013 04:07:26 +0000 (15:07 +1100)]
kexec, vmalloc: export additional vmalloc layer information
Now, vmap_area_list is exported as VMCOREINFO for makedumpfile to get the
start address of vmalloc region (vmalloc_start). The address which
contains vmalloc_start value is represented as below:
Joonsoo Kim [Wed, 20 Mar 2013 04:07:26 +0000 (15:07 +1100)]
mm, vmalloc: export vmap_area_list, instead of vmlist
Although our intention is to unexport internal structure entirely, but
there is one exception for kexec. kexec dumps address of vmlist and
makedumpfile uses this information.
We are about to remove vmlist, then another way to retrieve information of
vmalloc layer is needed for makedumpfile. For this purpose, we export
vmap_area_list, instead of vmlist.
Signed-off-by: Joonsoo Kim <js1304@gmail.com> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Eric Biederman <ebiederm@xmission.com> Cc: Dave Anderson <anderson@redhat.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Guan Xuetao <gxt@mprc.pku.edu.cn> Cc: Ingo Molnar <mingo@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Joonsoo Kim [Wed, 20 Mar 2013 04:07:26 +0000 (15:07 +1100)]
mm, vmalloc: iterate vmap_area_list, instead of vmlist, in vmallocinfo()
This patch is a preparatory step for removing vmlist entirely. For above
purpose, we change iterating a vmap_list codes to iterating a
vmap_area_list. It is somewhat trivial change, but just one thing should
be noticed.
Using vmap_area_list in vmallocinfo() introduce ordering problem in SMP
system. In s_show(), we retrieve some values from vm_struct. vm_struct's
values is not fully setup when va->vm is assigned. Full setup is notified
by removing VM_UNLIST flag without holding a lock. When we see that
VM_UNLIST is removed, it is not ensured that vm_struct has proper values
in view of other CPUs. So we need smp_[rw]mb for ensuring that proper
values is assigned when we see that VM_UNLIST is removed.
Therefore, this patch not only change a iteration list, but also add a
appropriate smp_[rw]mb to right places.
Signed-off-by: Joonsoo Kim <js1304@gmail.com> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Dave Anderson <anderson@redhat.com> Cc: Eric Biederman <ebiederm@xmission.com> Cc: Guan Xuetao <gxt@mprc.pku.edu.cn> Cc: Ingo Molnar <mingo@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Joonsoo Kim [Wed, 20 Mar 2013 04:07:25 +0000 (15:07 +1100)]
mm, vmalloc: iterate vmap_area_list in get_vmalloc_info()
This patch is a preparatory step for removing vmlist entirely. For above
purpose, we change iterating a vmap_list codes to iterating a
vmap_area_list. It is somewhat trivial change, but just one thing should
be noticed.
vmlist is lack of information about some areas in vmalloc address space.
For example, vm_map_ram() allocate area in vmalloc address space, but it
doesn't make a link with vmlist. To provide full information about
vmalloc address space is better idea, so we don't use va->vm and use
vmap_area directly. This makes get_vmalloc_info() more precise.
Signed-off-by: Joonsoo Kim <js1304@gmail.com> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Dave Anderson <anderson@redhat.com> Cc: Eric Biederman <ebiederm@xmission.com> Cc: Guan Xuetao <gxt@mprc.pku.edu.cn> Cc: Ingo Molnar <mingo@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Joonsoo Kim [Wed, 20 Mar 2013 04:07:25 +0000 (15:07 +1100)]
mm, vmalloc: iterate vmap_area_list, instead of vmlist in vread/vwrite()
Now, when we hold a vmap_area_lock, va->vm can't be discarded. So we can
safely access to va->vm when iterating a vmap_area_list with holding a
vmap_area_lock. With this property, change iterating vmlist codes in
vread/vwrite() to iterating vmap_area_list.
There is a little difference relate to lock, because vmlist_lock is mutex,
but, vmap_area_lock is spin_lock. It may introduce a spinning overhead
during vread/vwrite() is executing. But, these are debug-oriented
functions, so this overhead is not real problem for common case.
Signed-off-by: Joonsoo Kim <js1304@gmail.com> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Dave Anderson <anderson@redhat.com> Cc: Eric Biederman <ebiederm@xmission.com> Cc: Guan Xuetao <gxt@mprc.pku.edu.cn> Cc: Ingo Molnar <mingo@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Joonsoo Kim [Wed, 20 Mar 2013 04:07:25 +0000 (15:07 +1100)]
mm, vmalloc: protect va->vm by vmap_area_lock
Inserting and removing an entry to vmlist is linear time complexity, so it
is inefficient. Following patches will try to remove vmlist entirely.
This patch is preparing step for it.
For removing vmlist, iterating vmlist codes should be changed to iterating
a vmap_area_list. Before implementing that, we should make sure that when
we iterate a vmap_area_list, accessing to va->vm doesn't cause a race
condition. This patch ensure that when iterating a vmap_area_list, there
is no race condition for accessing to vm_struct.
Signed-off-by: Joonsoo Kim <js1304@gmail.com> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Dave Anderson <anderson@redhat.com> Cc: Eric Biederman <ebiederm@xmission.com> Cc: Guan Xuetao <gxt@mprc.pku.edu.cn> Cc: Ingo Molnar <mingo@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Joonsoo Kim [Wed, 20 Mar 2013 04:07:24 +0000 (15:07 +1100)]
mm, vmalloc: move get_vmalloc_info() to vmalloc.c
Now get_vmalloc_info() is in fs/proc/mmu.c. There is no reason that this
code must be here and it's implementation needs vmlist_lock and it iterate
a vmlist which may be internal data structure for vmalloc.
It is preferable that vmlist_lock and vmlist is only used in vmalloc.c
for maintainability. So move the code to vmalloc.c
Signed-off-by: Joonsoo Kim <js1304@gmail.com> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Dave Anderson <anderson@redhat.com> Cc: Eric Biederman <ebiederm@xmission.com> Cc: Guan Xuetao <gxt@mprc.pku.edu.cn> Cc: Ingo Molnar <mingo@kernel.org> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Joonsoo Kim [Wed, 20 Mar 2013 04:07:24 +0000 (15:07 +1100)]
mm, vmalloc: change iterating a vmlist to find_vm_area()
This patchset removes vm_struct list management after initializing
vmalloc. Adding and removing an entry to vmlist is linear time
complexity, so it is inefficient. If we maintain this list, overall time
complexity of adding and removing area to vmalloc space is O(N), although
we use rbtree for finding vacant place and it's time complexity is just
O(logN).
And vmlist and vmlist_lock is used many places of outside of vmalloc.c.
It is preferable that we hide this raw data structure and provide
well-defined function for supporting them, because it makes that they
cannot mistake when manipulating theses structure and it makes us easily
maintain vmalloc layer.
For kexec and makedumpfile, I export vmap_area_list, instead of vmlist.
This comes from Atsushi's recommendation. For more information, please
refer below link. https://lkml.org/lkml/2012/12/6/184
This patch:
The purpose of iterating a vmlist is finding vm area with specific virtual
address. find_vm_area() is provided for this purpose and more efficient,
because it uses a rbtree. So change it.
Signed-off-by: Joonsoo Kim <js1304@gmail.com> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Guan Xuetao <gxt@mprc.pku.edu.cn> Acked-by: Ingo Molnar <mingo@kernel.org> Acked-by: Chris Metcalf <cmetcalf@tilera.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp> Cc: Dave Anderson <anderson@redhat.com> Cc: Eric Biederman <ebiederm@xmission.com> Cc: Vivek Goyal <vgoyal@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Darrick J. Wong <darrick.wong@oracle.com> Cc: Jan Kara <jack@suse.cz> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
rename _submit_bh()'s `flags' to `bio_flags', delobotomize the _submit_bh declaration
Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Artem Bityutskiy <dedekind1@gmail.com> Cc: Darrick J. Wong <darrick.wong@oracle.com> Cc: Jan Kara <jack@suse.cz> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Darrick J. Wong [Wed, 20 Mar 2013 04:07:23 +0000 (15:07 +1100)]
mm: make snapshotting pages for stable writes a per-bio operation
Walking a bio's page mappings has proved problematic, so create a new bio
flag to indicate that a bio's data needs to be snapshotted in order to
guarantee stable pages during writeback. Next, for the one user
(ext3/jbd) of snapshotting, hook all the places where writes can be
initiated without PG_writeback set, and set BIO_SNAP_STABLE there.
Finally, the MS_SNAP_STABLE mount flag (only used by ext3) is now
superfluous, so get rid of it.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Artem Bityutskiy <dedekind1@gmail.com> Cc: Jan Kara <jack@suse.cz> Cc: Jens Axboe <axboe@kernel.dk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Gerald Schaefer [Wed, 20 Mar 2013 04:07:23 +0000 (15:07 +1100)]
mm/hugetlb: add more arch-defined huge_pte functions
Commit abf09bed3c "s390/mm: implement software dirty bits" introduced
another difference in the pte layout vs. the pmd layout on s390,
thoroughly breaking the s390 support for hugetlbfs. This requires
replacing some more pte_xxx functions in mm/hugetlbfs.c with a
huge_pte_xxx version.
This patch introduces those huge_pte_xxx functions and their
generic implementation in asm-generic/hugetlb.h, which will now be
included on all architectures supporting hugetlbfs apart from s390.
This change will be a no-op for those architectures.
Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Hugh Dickins <hughd@google.com> Cc: Hillf Danton <dhillf@gmail.com> Acked-by: Michal Hocko <mhocko@suse.cz> [for !s390 parts] Cc: Tony Luck <tony.luck@intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Paul Mundt <lethal@linux-sh.org> Cc: "David S. Miller" <davem@davemloft.net> Cc: Chris Metcalf <cmetcalf@tilera.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Michal Hocko [Wed, 20 Mar 2013 04:07:22 +0000 (15:07 +1100)]
memcg: further simplify mem_cgroup_iter
mem_cgroup_iter basically does two things currently. It takes care of the
house keeping (reference counting, raclaim cookie) and it iterates through
a hierarchy tree (by using cgroup generic tree walk). The code would be
much more easier to follow if we move the iteration outside of the
function (to __mem_cgrou_iter_next) so the distinction is more clear.
This patch doesn't introduce any functional changes.
Signed-off-by: Michal Hocko <mhocko@suse.cz> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Li Zefan <lizefan@huawei.com> Cc: Ying Han <yinghan@google.com> Cc: Tejun Heo <htejun@gmail.com> Cc: Glauber Costa <glommer@parallels.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Michal Hocko [Wed, 20 Mar 2013 04:07:22 +0000 (15:07 +1100)]
memcg: simplify mem_cgroup_iter
Current implementation of mem_cgroup_iter has to consider both css and
memcg to find out whether no group has been found (css==NULL - aka the
loop is completed) and that no memcg is associated with the found node
(!memcg - aka css_tryget failed because the group is no longer alive).
This leads to awkward tweaks like tests for css && !memcg to skip the
current node.
It will be much easier if we got rid off css variable altogether and only
rely on memcg. In order to do that the iteration part has to skip dead
nodes. This sounds natural to me and as a nice side effect we will get a
simple invariant that memcg is always alive when non-NULL and all nodes
have been visited otherwise.
We could get rid of the surrounding while loop but keep it in for now to
make review easier. It will go away in the following patch.
Signed-off-by: Michal Hocko <mhocko@suse.cz> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Li Zefan <lizefan@huawei.com> Cc: Ying Han <yinghan@google.com> Cc: Tejun Heo <htejun@gmail.com> Cc: Glauber Costa <glommer@parallels.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Michal Hocko [Wed, 20 Mar 2013 04:07:21 +0000 (15:07 +1100)]
memcg: relax memcg iter caching
Now that per-node-zone-priority iterator caches memory cgroups rather than
their css ids we have to be careful and remove them from the iterator when
they are on the way out otherwise they might live for unbounded amount of
time even though their group is already gone (until the global/targeted
reclaim triggers the zone under priority to find out the group is dead and
let it to find the final rest).
We can fix this issue by relaxing rules for the last_visited memcg.
Instead of taking a reference to the css before it is stored into
iter->last_visited we can just store its pointer and track the number of
removed groups from each memcg's subhierarchy.
This number would be stored into iterator everytime when a memcg is
cached. If the iter count doesn't match the curent walker root's one we
will start from the root again. The group counter is incremented upwards
the hierarchy every time a group is removed.
The iter_lock can be dropped because racing iterators cannot leak the
reference anymore as the reference count is not elevated for last_visited
when it is cached.
Locking rules got a bit complicated by this change though. The iterator
primarily relies on rcu read lock which makes sure that once we see a
valid last_visited pointer then it will be valid for the whole RCU walk.
smp_rmb makes sure that dead_count is read before last_visited and
last_dead_count while smp_wmb makes sure that last_visited is updated
before last_dead_count so the up-to-date last_dead_count cannot point to
an outdated last_visited. css_tryget then makes sure that the
last_visited is still alive in case the iteration races with the cached
group removal (css is invalidated before mem_cgroup_css_offline increments
dead_count).
In short:
mem_cgroup_iter
rcu_read_lock()
dead_count = atomic_read(parent->dead_count)
smp_rmb()
if (dead_count != iter->last_dead_count)
last_visited POSSIBLY INVALID -> last_visited = NULL
if (!css_tryget(iter->last_visited))
last_visited DEAD -> last_visited = NULL
next = find_next(last_visited)
css_tryget(next)
css_put(last_visited) // css would be invalidated and parent->dead_count
// incremented if this was the last reference
iter->last_visited = next
smp_wmb()
iter->last_dead_count = dead_count
rcu_read_unlock()
cgroup_rmdir
cgroup_destroy_locked
atomic_add(CSS_DEACT_BIAS, &css->refcnt) // subsequent css_tryget fail
mem_cgroup_css_offline
mem_cgroup_invalidate_reclaim_iterators
while(parent = parent_mem_cgroup)
atomic_inc(parent->dead_count)
css_put(css) // last reference held by cgroup core
Spotted by Ying Han.
Original idea from Johannes Weiner.
Signed-off-by: Michal Hocko <mhocko@suse.cz> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Ying Han <yinghan@google.com> Cc: Li Zefan <lizefan@huawei.com> Cc: Tejun Heo <htejun@gmail.com> Cc: Glauber Costa <glommer@parallels.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Michal Hocko [Wed, 20 Mar 2013 04:07:21 +0000 (15:07 +1100)]
memcg: rework mem_cgroup_iter to use cgroup iterators
mem_cgroup_iter curently relies on css->id when walking down a group
hierarchy tree. This is really awkward because the tree walk depends on
the groups creation ordering. The only guarantee is that a parent node is
visited before its children.
Example:
1) mkdir -p a a/d a/b/c
2) mkdir -a a/b/c a/d
Will create the same trees but the tree walks will be different:
1) a, d, b, c
2) a, b, c, d
574bd9f7 ("cgroup: implement generic child / descendant walk macros") has
introduced generic cgroup tree walkers which provide either pre-order or
post-order tree walk. This patch converts css->id based iteration to
pre-order tree walk to keep the semantic with the original iterator where
parent is always visited before its subtree.
cgroup_for_each_descendant_pre suggests using post_create and pre_destroy
for proper synchronization with groups addidition resp. removal. This
implementation doesn't use those because a new memory cgroup is
initialized sufficiently for iteration in mem_cgroup_css_alloc already and
css reference counting enforces that the group is alive for both the last
seen cgroup and the found one resp. it signals that the group is dead and
it should be skipped.
If the reclaim cookie is used we need to store the last visited group into
the iterator so we have to be careful that it doesn't disappear in the
mean time. Elevated reference count on the css keeps it alive even though
the group have been removed (parked waiting for the last dput so that it
can be freed).
Per node-zone-prio iter_lock has been introduced to ensure that css_tryget
and iter->last_visited is set atomically. Otherwise two racing walkers
could both take a references and only one release it leading to a css leak
(which pins cgroup dentry).
Signed-off-by: Michal Hocko <mhocko@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Li Zefan <lizefan@huawei.com> Cc: Ying Han <yinghan@google.com> Cc: Tejun Heo <htejun@gmail.com> Cc: Glauber Costa <glommer@parallels.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Michal Hocko [Wed, 20 Mar 2013 04:07:21 +0000 (15:07 +1100)]
memcg: keep prev's css alive for the whole mem_cgroup_iter
The patchset tries to make mem_cgroup_iter saner in the way how it walks
hierarchies. css->id based traversal is far from being ideal as it is not
deterministic because it depends on the creation ordering. Additional to
that css_id is considered a burden for cgroup maintainers because it is
quite some code and memcg is the last user of it. After this series only
the swap accounting uses css_id but that one will follow up later.
The first patch is just preparatory and it changes when we release css of
the previously returned memcg. Nothing controlversial.
The second patch is the core of the patchset and it replaces css_get_next
based on css_id by the generic cgroup pre-order. This brings some
chalanges for the last visited group caching during the reclaim
(mem_cgroup_per_zone::reclaim_iter). We have to use memcg pointers
directly now which means that we have to keep a reference to those groups'
css to keep them alive.
I also folded iter_lock introduced by https://lkml.org/lkml/2013/1/3/295
in the previous version into this patch. Johannes felt the race I was
describing should be mostly harmless and I haven't been able to trigger it
so the lock doesn't deserve its own patch. It is still needed
temporarily, though, because the reference counting on iter->last_visited
depends on it. It will go away with the next patch.
The next patch fixups an unbounded cgroup removal holdoff caused by the
elevated css refcount. The issue has been observed by Ying Han. Johannes
wasn't impressed by the previous version of the fix
(https://lkml.org/lkml/2013/2/8/379) which cleaned up pending references
during mem_cgroup_css_offline when a group is removed. He has suggested a
different way when the iterator checks whether a cached memcg is still
valid or no. More on that in the patch but the basic idea is that every
memcg tracks the number removed subgroups and iterator records this number
when a group is cached. These numbers are checked before
iter->last_visited is about to be used and the iteration is restarted if
it is invalid.
The fourth and fifth patches are an attempt for simplification of the
mem_cgroup_iter. css juggling is removed and the iteration logic is moved
to a helper so that the reference counting and iteration are separated.
The last patch just removes css_get_next as there is no user for it any
longer.
My testing looked as follows:
A (use_hierarchy=1, limit_in_bytes=150M)
/|\
1 2 3
Children groups were created so that the number is never higher than 3 and
their limits were random between 50-100M. Each group hosts a kernel build
(starting with tar -xf so the tree is not shared and make -jNUM_CPUs/3)
and terminated after random time - up to 5 minutes) and then it is
removed.
This should exercise both leaf and hierarchical reclaim as well as races
with cgroup removals and debugging messages I added on top proved that.
100 groups were created during the test.
This patch:
css reference counting keeps the cgroup alive even though it has been
already removed. mem_cgroup_iter relies on this fact and takes a
reference to the returned group. The reference is then released on the
next iteration or mem_cgroup_iter_break. mem_cgroup_iter currently
releases the reference right after it gets the last css_id.
This is correct because neither prev's memcg nor cgroup are accessed after
then. This will change in the next patch so we need to hold the group
alive a bit longer so let's move the css_put at the end of the function.
Signed-off-by: Michal Hocko <mhocko@suse.cz> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Li Zefan <lizefan@huawei.com> Cc: Ying Han <yinghan@google.com> Cc: Tejun Heo <htejun@gmail.com> Cc: Glauber Costa <glommer@parallels.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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