freezer: fix wait_event_freezable/__thaw_task races (24b7ead3) · Commits · 戴 / test

wait_event_freezable() and friends stop the waiting if try_to_freeze() fails. This is not right, we can race with __thaw_task() and in this case - wait_event_freezable() returns the wrong ERESTARTSYS - wait_event_freezable_timeout() can return the positive value while condition == F Change the code to always check __retval/condition before return. Note: with or without this patch the timeout logic looks strange, probably we should recalc timeout if try_to_freeze() returns T. Signed-off-by:

Oleg Nesterov <oleg@redhat.com> Acked-by:

Tejun Heo <tj@kernel.org>

include/linux/freezer.h

+10 −8

Original line number	Diff line number	Diff line
		@@ -122,28 +122,30 @@ static inline int freezer_should_skip(struct task_struct *p)
		#define wait_event_freezable(wq, condition) \
		({ \
		int __retval; \
		do { \
		for (;;) { \
		__retval = wait_event_interruptible(wq, \
		(condition) \|\| freezing(current)); \
		if (__retval && !freezing(current)) \
		if (__retval \|\| (condition)) \
		break; \
		else if (!(condition)) \
		__retval = -ERESTARTSYS; \
		} while (try_to_freeze()); \
		try_to_freeze(); \
		} \
		__retval; \
		})


		#define wait_event_freezable_timeout(wq, condition, timeout) \
		({ \
		long __retval = timeout; \
		do { \
		for (;;) { \
		__retval = wait_event_interruptible_timeout(wq, \
		(condition) \|\| freezing(current), \
		__retval); \
		} while (try_to_freeze()); \
		if (__retval <= 0 \|\| (condition)) \
		break; \
		try_to_freeze(); \
		} \
		__retval; \
		})

		#else /* !CONFIG_FREEZER */
		static inline bool frozen(struct task_struct *p) { return false; }
		static inline bool freezing(struct task_struct *p) { return false; }

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