Fix a bug identified by Zou Nan hai <nanhai.zou@intel.com>:
If the system is in state SYSTEM_BOOTING, and need_resched() is true,
cond_resched() returns true even though it didn't reschedule. Consequently
need_resched() remains true and JBD locks up.
Fix that by teaching cond_resched() to only return true if it really did call
schedule().
cond_resched_lock() and cond_resched_softirq() have a problem too. If we're
in SYSTEM_BOOTING state and need_resched() is true, these functions will drop
the lock and will then try to call schedule(), but the SYSTEM_BOOTING state
will prevent schedule() from being called. So on return, need_resched() will
still be true, but cond_resched_lock() has to return 1 to tell the caller that
the lock was dropped. The caller will probably lock up.
Bottom line: if these functions dropped the lock, they _must_ call schedule()
to clear need_resched(). Make it so.
Also, uninline __cond_resched(). It's largeish, and slowpath.
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
e7b384043e