[v2,0/3] mm/kmemleak: Avoid soft lockup in kmemleak_scan()

Message

Waiman Long June 14, 2022, 10:03 p.m. UTC

v2:
  - Update patch 3 to count the objects checked instead of being
    gray for determining when to do cond_resched(). This is more
    reliable.

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.

Waiman Long (3):
  mm/kmemleak: Use _irq lock/unlock variants in kmemleak_scan/_clear()
  mm/kmemleak: Skip unlikely objects in kmemleak_scan() without taking
    lock
  mm/kmemleak: Prevent soft lockup in first object iteration loop of
    kmemleak_scan()

 mm/kmemleak.c | 60 +++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 49 insertions(+), 11 deletions(-)