]> git.karo-electronics.de Git - karo-tx-linux.git/commitdiff
rcu: Allow rcu_user_enter()/exit() to nest
authorFrederic Weisbecker <fweisbec@gmail.com>
Wed, 11 Jul 2012 18:26:31 +0000 (20:26 +0200)
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Tue, 31 Jul 2012 17:32:40 +0000 (10:32 -0700)
Allow calls to rcu_user_enter() even if we are already
in userspace (as seen by RCU) and allow calls to rcu_user_exit()
even if we are already in the kernel.

This makes the APIs more flexible to be called from architectures.
Exception entries for example won't need to know if they come from
userspace before calling rcu_user_exit().

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
kernel/rcutree.c
kernel/rcutree.h

index e287c4a0d81c083c86df312f8c5c7fe305a511fe..8bbc7fbc289f2b01b97ee2ad779801bc05a04a95 100644 (file)
@@ -390,11 +390,9 @@ static void rcu_eqs_enter_common(struct rcu_dynticks *rdtp, long long oldval,
  */
 static void rcu_eqs_enter(bool user)
 {
-       unsigned long flags;
        long long oldval;
        struct rcu_dynticks *rdtp;
 
-       local_irq_save(flags);
        rdtp = &__get_cpu_var(rcu_dynticks);
        oldval = rdtp->dynticks_nesting;
        WARN_ON_ONCE((oldval & DYNTICK_TASK_NEST_MASK) == 0);
@@ -403,7 +401,6 @@ static void rcu_eqs_enter(bool user)
        else
                rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE;
        rcu_eqs_enter_common(rdtp, oldval, user);
-       local_irq_restore(flags);
 }
 
 /**
@@ -420,7 +417,11 @@ static void rcu_eqs_enter(bool user)
  */
 void rcu_idle_enter(void)
 {
+       unsigned long flags;
+
+       local_irq_save(flags);
        rcu_eqs_enter(0);
+       local_irq_restore(flags);
 }
 EXPORT_SYMBOL_GPL(rcu_idle_enter);
 
@@ -435,7 +436,18 @@ EXPORT_SYMBOL_GPL(rcu_idle_enter);
  */
 void rcu_user_enter(void)
 {
-       rcu_eqs_enter(1);
+       unsigned long flags;
+       struct rcu_dynticks *rdtp;
+
+       WARN_ON_ONCE(!current->mm);
+
+       local_irq_save(flags);
+       rdtp = &__get_cpu_var(rcu_dynticks);
+       if (!rdtp->in_user) {
+               rdtp->in_user = true;
+               rcu_eqs_enter(1);
+       }
+       local_irq_restore(flags);
 }
 EXPORT_SYMBOL_GPL(rcu_user_enter);
 
@@ -530,11 +542,9 @@ static void rcu_eqs_exit_common(struct rcu_dynticks *rdtp, long long oldval,
  */
 static void rcu_eqs_exit(bool user)
 {
-       unsigned long flags;
        struct rcu_dynticks *rdtp;
        long long oldval;
 
-       local_irq_save(flags);
        rdtp = &__get_cpu_var(rcu_dynticks);
        oldval = rdtp->dynticks_nesting;
        WARN_ON_ONCE(oldval < 0);
@@ -543,7 +553,6 @@ static void rcu_eqs_exit(bool user)
        else
                rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
        rcu_eqs_exit_common(rdtp, oldval, user);
-       local_irq_restore(flags);
 }
 
 /**
@@ -559,7 +568,11 @@ static void rcu_eqs_exit(bool user)
  */
 void rcu_idle_exit(void)
 {
+       unsigned long flags;
+
+       local_irq_save(flags);
        rcu_eqs_exit(0);
+       local_irq_restore(flags);
 }
 EXPORT_SYMBOL_GPL(rcu_idle_exit);
 
@@ -572,7 +585,16 @@ EXPORT_SYMBOL_GPL(rcu_idle_exit);
  */
 void rcu_user_exit(void)
 {
-       rcu_eqs_exit(1);
+       unsigned long flags;
+       struct rcu_dynticks *rdtp;
+
+       local_irq_save(flags);
+       rdtp = &__get_cpu_var(rcu_dynticks);
+       if (rdtp->in_user) {
+               rdtp->in_user = false;
+               rcu_eqs_exit(1);
+       }
+       local_irq_restore(flags);
 }
 EXPORT_SYMBOL_GPL(rcu_user_exit);
 
@@ -2590,6 +2612,9 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
        rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
        WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE);
        WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1);
+#ifdef CONFIG_RCU_USER_QS
+       WARN_ON_ONCE(rdp->dynticks->in_user);
+#endif
        rdp->cpu = cpu;
        rdp->rsp = rsp;
        raw_spin_unlock_irqrestore(&rnp->lock, flags);
index 4d29169f212468bdc6f8dd17311ecf8bdd6850a8..0dd5fd6e794cab98a943a2cc08b1c7a99014af2f 100644 (file)
@@ -102,6 +102,9 @@ struct rcu_dynticks {
                                    /* idle-period nonlazy_posted snapshot. */
        int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */
 #endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
+#ifdef CONFIG_RCU_USER_QS
+       bool in_user;               /* Is the CPU in userland from RCU POV? */
+#endif
 };
 
 /* RCU's kthread states for tracing. */