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With the use of wake_q, we can do task wakeups without holding the wait_lock. There is one exception in the rwsem code, though. It is when the writer in the slowpath detects that there are waiters ahead but the rwsem is not held by a writer. This can lead to a long wait_lock hold time especially when a large number of readers are to be woken up. Remediate this situation by releasing the wait_lock before waking up tasks and re-acquiring it afterward. The rwsem_try_write_lock() function is also modified to read the rwsem count directly to avoid stale count value. Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Will Deacon <will.deacon@arm.com> Cc: huang ying <huang.ying.caritas@gmail.com> Link: https://lkml.kernel.org/r/20190520205918.22251-9-longman@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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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 | ||