From: Steven Rostedt <rostedt@xxxxxxxxxxx> 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@xxxxxxxxxxx> Cc: Carsten Emde <C.Emde@xxxxxxxxx> Cc: John Kacur <jkacur@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Clark Williams <clark.williams@xxxxxxxxx> Cc: stable-rt@xxxxxxxxxxxxxxx Link: http://lkml.kernel.org/r/20120301190345.374756214@xxxxxxxxxxx Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> --- 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 d8acbcc..9cfab36 100644 --- a/include/linux/lglock.h +++ b/include/linux/lglock.h @@ -204,9 +204,31 @@ #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); \ @@ -215,6 +237,11 @@ 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); \ \ @@ -255,7 +282,8 @@ 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); \ @@ -266,11 +294,12 @@ 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); \ \ -- 1.7.8.3 -- To unsubscribe from this list: send the line "unsubscribe stable-rt" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
