diff options
| author | Steven Rostedt <rostedt@goodmis.org> | 2012-03-01 13:55:30 -0500 |
|---|---|---|
| committer | Clark Williams <williams@redhat.com> | 2012-03-14 10:50:16 -0500 |
| commit | 11752d3ed34b455a1ff6c4b370b7f4a145f242d0 (patch) | |
| tree | 535142cb6599c53a6b4043b3f46587e167a37da9 | |
| parent | b02eac89fd413a802220ae0407922893a49a6380 (diff) | |
lglock/rt: Use non-rt for_each_cpu() in -rt code
Currently the RT version of the lglocks() does a for_each_online_cpu()
in the name##_global_lock_online() functions. Non-rt uses its own
mask for this, and for good reason.
A task may grab a *_global_lock_online(), and in the mean time, one
of the CPUs goes offline. Now when that task does a *_global_unlock_online()
it releases all the locks *except* the one that went offline.
Now if that CPU were to come back on line, its lock is now owned by a
task that never released it when it should have.
This causes all sorts of fun errors. Like owners of a lock no longer
existing, or sleeping on IO, waiting to be woken up by a task that
happens to be blocked on the lock it never released.
Convert the RT versions to use the lglock specific cpumasks. As once
a CPU comes on line, the mask is set, and never cleared even when the
CPU goes offline. The locks for that CPU will still be taken and released.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Carsten Emde <C.Emde@osadl.org>
Cc: John Kacur <jkacur@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Clark Williams <clark.williams@gmail.com>
Cc: stable-rt@vger.kernel.org
Link: http://lkml.kernel.org/r/20120301190345.374756214@goodmis.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| -rw-r--r-- | include/linux/lglock.h | 35 |
1 files changed, 32 insertions, 3 deletions
diff --git a/include/linux/lglock.h b/include/linux/lglock.h index 52b289f02feb..cdfcef312c79 100644 --- a/include/linux/lglock.h +++ b/include/linux/lglock.h @@ -203,9 +203,31 @@ #else /* !PREEMPT_RT_FULL */ #define DEFINE_LGLOCK(name) \ \ - DEFINE_PER_CPU(struct rt_mutex, name##_lock); \ + DEFINE_PER_CPU(struct rt_mutex, name##_lock); \ + DEFINE_SPINLOCK(name##_cpu_lock); \ + cpumask_t name##_cpus __read_mostly; \ DEFINE_LGLOCK_LOCKDEP(name); \ \ + static int \ + name##_lg_cpu_callback(struct notifier_block *nb, \ + unsigned long action, void *hcpu) \ + { \ + switch (action & ~CPU_TASKS_FROZEN) { \ + case CPU_UP_PREPARE: \ + spin_lock(&name##_cpu_lock); \ + cpu_set((unsigned long)hcpu, name##_cpus); \ + spin_unlock(&name##_cpu_lock); \ + break; \ + case CPU_UP_CANCELED: case CPU_DEAD: \ + spin_lock(&name##_cpu_lock); \ + cpu_clear((unsigned long)hcpu, name##_cpus); \ + spin_unlock(&name##_cpu_lock); \ + } \ + return NOTIFY_OK; \ + } \ + static struct notifier_block name##_lg_cpu_notifier = { \ + .notifier_call = name##_lg_cpu_callback, \ + }; \ void name##_lock_init(void) { \ int i; \ LOCKDEP_INIT_MAP(&name##_lock_dep_map, #name, &name##_lock_key, 0); \ @@ -214,6 +236,11 @@ lock = &per_cpu(name##_lock, i); \ rt_mutex_init(lock); \ } \ + register_hotcpu_notifier(&name##_lg_cpu_notifier); \ + get_online_cpus(); \ + for_each_online_cpu(i) \ + cpu_set(i, name##_cpus); \ + put_online_cpus(); \ } \ EXPORT_SYMBOL(name##_lock_init); \ \ @@ -254,7 +281,8 @@ void name##_global_lock_online(void) { \ int i; \ rwlock_acquire(&name##_lock_dep_map, 0, 0, _RET_IP_); \ - for_each_online_cpu(i) { \ + spin_lock(&name##_cpu_lock); \ + for_each_cpu(i, &name##_cpus) { \ struct rt_mutex *lock; \ lock = &per_cpu(name##_lock, i); \ __rt_spin_lock(lock); \ @@ -265,11 +293,12 @@ void name##_global_unlock_online(void) { \ int i; \ rwlock_release(&name##_lock_dep_map, 1, _RET_IP_); \ - for_each_online_cpu(i) { \ + for_each_cpu(i, &name##_cpus) { \ struct rt_mutex *lock; \ lock = &per_cpu(name##_lock, i); \ __rt_spin_unlock(lock); \ } \ + spin_unlock(&name##_cpu_lock); \ } \ EXPORT_SYMBOL(name##_global_unlock_online); \ \ |