mm/kmemleak: use _irq lock/unlock variants in kmemleak_scan/_clear()
Patch series "mm/kmemleak: Avoid soft lockup in kmemleak_scan()", v2.
There are 3 RCU-based object iteration loops in kmemleak_scan(). Because
of the need to take RCU read lock, we can't insert cond_resched() into the
loop like other parts of the function. As there can be millions of
objects to be scanned, it takes a while to iterate all of them. The
kmemleak functionality is usually enabled in a debug kernel which is much
slower than a non-debug kernel. With sufficient number of kmemleak
objects, the time to iterate them all may exceed 22s causing soft lockup.
watchdog: BUG: soft lockup - CPU#3 stuck for 22s! [kmemleak:625]
This patch series make changes to the 3 object iteration loops in
kmemleak_scan() to prevent them from causing soft lockup.
This patch (of 3):
kmemleak_scan() is called only from the kmemleak scan thread or from write
to the kmemleak debugfs file. Both are in task context and so we can
directly use the simpler _irq() lock/unlock calls instead of the more
complex _irqsave/_irqrestore variants.
Similarly, kmemleak_clear() is called only from write to the kmemleak
debugfs file. The same change can be applied.
Link: https://lkml.kernel.org/r/20220614220359.59282-1-longman@redhat.com
Link: https://lkml.kernel.org/r/20220614220359.59282-2-longman@redhat.com
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>