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debugobjects,locking: Annotate debug_object_fill_pool() wait type violation

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There is an explicit wait-type violation in debug_object_fill_pool()
for PREEMPT_RT=n kernels which allows them to more easily fill the
object pool and reduce the chance of allocation failures.

Lockdep's wait-type checks are designed to check the PREEMPT_RT
locking rules even for PREEMPT_RT=n kernels and object to this, so
create a lockdep annotation to allow this to stand.

Specifically, create a 'lock' type that overrides the inner wait-type
while it is held -- allowing one to temporarily raise it, such that
the violation is hidden.

Reported-by: Vlastimil Babka <vbabka@suse.cz>
Reported-by: Qi Zheng <zhengqi.arch@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Qi Zheng <zhengqi.arch@bytedance.com>
Link: https://lkml.kernel.org/r/20230429100614.GA1489784@hirez.programming.kicks-ass.net
This commit is contained in:
Peter Zijlstra
2023-04-25 17:03:13 +02:00
parent 0af462f19e
commit 0cce06ba85
4 changed files with 49 additions and 9 deletions
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15
lib/debugobjects.c
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@@ -591,10 +591,21 @@ static void debug_objects_fill_pool(void)
{
/*
* On RT enabled kernels the pool refill must happen in preemptible
* context:
* context -- for !RT kernels we rely on the fact that spinlock_t and
* raw_spinlock_t are basically the same type and this lock-type
* inversion works just fine.
*/
if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible())
if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible()) {
/*
* Annotate away the spinlock_t inside raw_spinlock_t warning
* by temporarily raising the wait-type to WAIT_SLEEP, matching
* the preemptible() condition above.
*/
static DEFINE_WAIT_OVERRIDE_MAP(fill_pool_map, LD_WAIT_SLEEP);
lock_map_acquire_try(&fill_pool_map);
fill_pool();
lock_map_release(&fill_pool_map);
}
}
static void