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Currently, the chainkey of a lock chain is a hash sum of the class_idx
of all the held locks, the read/write status are not taken in to
consideration while generating the chainkey. This could result into a
problem, if we have:
P1()
{
read_lock(B);
lock(A);
}
P2()
{
lock(A);
read_lock(B);
}
P3()
{
lock(A);
write_lock(B);
}
, and P1(), P2(), P3() run one by one. And when running P2(), lockdep
detects such a lock chain A -> B is not a deadlock, then it's added in
the chain cache, and then when running P3(), even if it's a deadlock, we
could miss it because of the hit of chain cache. This could be confirmed
by self testcase "chain cached mixed R-L/L-W ".
To resolve this, we use concept "hlock_id" to generate the chainkey, the
hlock_id is a tuple (hlock->class_idx, hlock->read), which fits in a u16
type. With this, the chainkeys are different is the lock sequences have
the same locks but different read/write status.
Besides, since we use "hlock_id" to generate chainkeys, the chain_hlocks
array now store the "hlock_id"s rather than lock_class indexes.
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200807074238.1632519-15-boqun.feng@gmail.com
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|---|---|---|
| .. | ||
| lock_events.c | ||
| lock_events.h | ||
| lock_events_list.h | ||
| lockdep.c | ||
| lockdep_internals.h | ||
| lockdep_proc.c | ||
| lockdep_states.h | ||
| locktorture.c | ||
| Makefile | ||
| mcs_spinlock.h | ||
| mutex-debug.c | ||
| mutex-debug.h | ||
| mutex.c | ||
| mutex.h | ||
| osq_lock.c | ||
| percpu-rwsem.c | ||
| qrwlock.c | ||
| qspinlock.c | ||
| qspinlock_paravirt.h | ||
| qspinlock_stat.h | ||
| rtmutex-debug.c | ||
| rtmutex-debug.h | ||
| rtmutex.c | ||
| rtmutex.h | ||
| rtmutex_common.h | ||
| rwsem.c | ||
| rwsem.h | ||
| semaphore.c | ||
| spinlock.c | ||
| spinlock_debug.c | ||
| test-ww_mutex.c | ||