From 62c6c61adbc623cdacf74b8f29c278e539060c48 Mon Sep 17 00:00:00 2001 From: Yang Shi Date: Mon, 5 Oct 2015 14:32:51 -0700 Subject: [PATCH] arm64: replace read_lock to rcu lock in call_break_hook BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:917 in_atomic(): 0, irqs_disabled(): 128, pid: 342, name: perf 1 lock held by perf/342: #0: (break_hook_lock){+.+...}, at: [] call_break_hook+0x34/0xd0 irq event stamp: 62224 hardirqs last enabled at (62223): [] __call_rcu.constprop.59+0x104/0x270 hardirqs last disabled at (62224): [] vprintk_emit+0x68/0x640 softirqs last enabled at (0): [] copy_process.part.8+0x428/0x17f8 softirqs last disabled at (0): [< (null)>] (null) CPU: 0 PID: 342 Comm: perf Not tainted 4.1.6-rt5 #4 Hardware name: linux,dummy-virt (DT) Call trace: [] dump_backtrace+0x0/0x128 [] show_stack+0x20/0x30 [] dump_stack+0x7c/0xa0 [] ___might_sleep+0x174/0x260 [] __rt_spin_lock+0x28/0x40 [] rt_read_lock+0x60/0x80 [] call_break_hook+0x30/0xd0 [] brk_handler+0x30/0x98 [] do_debug_exception+0x50/0xb8 Exception stack(0xffffffc00514fe30 to 0xffffffc00514ff50) fe20: 00000000 00000000 c1594680 0000007f fe40: ffffffff ffffffff 92063940 0000007f 0550dcd8 ffffffc0 00000000 00000000 fe60: 0514fe70 ffffffc0 000be1f8 ffffffc0 0514feb0 ffffffc0 0008948c ffffffc0 fe80: 00000004 00000000 0514fed0 ffffffc0 ffffffff ffffffff 9282a948 0000007f fea0: 00000000 00000000 9282b708 0000007f c1592820 0000007f 00083914 ffffffc0 fec0: 00000000 00000000 00000010 00000000 00000064 00000000 00000001 00000000 fee0: 005101e0 00000000 c1594680 0000007f c1594740 0000007f ffffffd8 ffffff80 ff00: 00000000 00000000 00000000 00000000 c1594770 0000007f c1594770 0000007f ff20: 00665e10 00000000 7f7f7f7f 7f7f7f7f 01010101 01010101 00000000 00000000 ff40: 928e4cc0 0000007f 91ff11e8 0000007f call_break_hook is called in atomic context (hard irq disabled), so replace the sleepable lock to rcu lock, replace relevant list operations to rcu version and call synchronize_rcu() in unregister_break_hook(). And, replace write lock to spinlock in {un}register_break_hook. Signed-off-by: Yang Shi Signed-off-by: Will Deacon --- arch/arm64/kernel/debug-monitors.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-) diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c index 8eef30f92651..253021ef2769 100644 --- a/arch/arm64/kernel/debug-monitors.c +++ b/arch/arm64/kernel/debug-monitors.c @@ -271,20 +271,21 @@ static int single_step_handler(unsigned long addr, unsigned int esr, * Use reader/writer locks instead of plain spinlock. */ static LIST_HEAD(break_hook); -static DEFINE_RWLOCK(break_hook_lock); +static DEFINE_SPINLOCK(break_hook_lock); void register_break_hook(struct break_hook *hook) { - write_lock(&break_hook_lock); - list_add(&hook->node, &break_hook); - write_unlock(&break_hook_lock); + spin_lock(&break_hook_lock); + list_add_rcu(&hook->node, &break_hook); + spin_unlock(&break_hook_lock); } void unregister_break_hook(struct break_hook *hook) { - write_lock(&break_hook_lock); - list_del(&hook->node); - write_unlock(&break_hook_lock); + spin_lock(&break_hook_lock); + list_del_rcu(&hook->node); + spin_unlock(&break_hook_lock); + synchronize_rcu(); } static int call_break_hook(struct pt_regs *regs, unsigned int esr) @@ -292,11 +293,11 @@ static int call_break_hook(struct pt_regs *regs, unsigned int esr) struct break_hook *hook; int (*fn)(struct pt_regs *regs, unsigned int esr) = NULL; - read_lock(&break_hook_lock); - list_for_each_entry(hook, &break_hook, node) + rcu_read_lock(); + list_for_each_entry_rcu(hook, &break_hook, node) if ((esr & hook->esr_mask) == hook->esr_val) fn = hook->fn; - read_unlock(&break_hook_lock); + rcu_read_unlock(); return fn ? fn(regs, esr) : DBG_HOOK_ERROR; } -- 2.39.2