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authorSteven Rostedt <rostedt@goodmis.org>2012-03-01 13:55:30 -0500
committerClark Williams <williams@redhat.com>2012-04-13 11:01:53 -0500
commit639d1576ea0c32dba976ba421e34cc1598bcc655 (patch)
tree9c6ba9d72e23a0fa7a85faf1d8707b7e98bb9559
parent477e065902b82f12e9d4a20852d6b170b45209ad (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.h35
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); \
\