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[PATCH] cpuset oom lock fix

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The problem, reported in:

  http://bugzilla.kernel.org/show_bug.cgi?id=5859

and by various other email messages and lkml posts is that the cpuset hook
in the oom (out of memory) code can try to take a cpuset semaphore while
holding the tasklist_lock (a spinlock).

One must not sleep while holding a spinlock.

The fix seems easy enough - move the cpuset semaphore region outside the
tasklist_lock region.

This required a few lines of mechanism to implement.  The oom code where
the locking needs to be changed does not have access to the cpuset locks,
which are internal to kernel/cpuset.c only.  So I provided a couple more
cpuset interface routines, available to the rest of the kernel, which
simple take and drop the lock needed here (cpusets callback_sem).

Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Paul Jackson 2006-01-14 13:21:06 -08:00 • committed by Linus Torvalds
parent ed68cb3676
commit 505970b96e
3 changed files with 37 additions and 5 deletions
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6
include/linux/cpuset.h
View file

@ -48,6 +48,9 @@ extern void __cpuset_memory_pressure_bump(void);
extern struct file_operations proc_cpuset_operations;
extern char *cpuset_task_status_allowed(struct task_struct *task, char *buffer);
extern void cpuset_lock(void);
extern void cpuset_unlock(void);
#else /* !CONFIG_CPUSETS */
static inline int cpuset_init_early(void) { return 0; }
@ -93,6 +96,9 @@ static inline char *cpuset_task_status_allowed(struct task_struct *task,
return buffer;
}
static inline void cpuset_lock(void) {}
static inline void cpuset_unlock(void) {}
#endif /* !CONFIG_CPUSETS */
#endif /* _LINUX_CPUSET_H */