hrtimer: raise softirq unlocked to avoid circular lock dependency
The scheduler hrtimer bits in 2.6.25 introduced a circular lock
dependency in a rare code path:
=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.25-sched-devel.git-x86-latest.git #19
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X/2980 is trying to acquire lock:
(&rq->rq_lock_key#2){++..}, at: [<ffffffff80230146>] task_rq_lock+0x56/0xa0
but task is already holding lock:
(&cpu_base->lock){++..}, at: [<ffffffff80257ae1>] lock_hrtimer_base+0x31/0x60
which lock already depends on the new lock.
The scenario which leads to this is:
posix-timer signal is delivered
-> posix-timer is rearmed
timer is already expired in hrtimer_enqueue()
-> softirq is raised
To prevent this we need to move the raise of the softirq out of the
base->lock protected code path.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@kernel.org
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
1 file changed
