From be3e7844980352756de4261b276ee2ba5be7a26b Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 24 May 2016 14:45:21 +0200 Subject: [PATCH] locking/spinlock: Update spin_unlock_wait() users With the modified semantics of spin_unlock_wait() a number of explicit barriers can be removed. Also update the comment for the do_exit() usecase, as that was somewhat stale/obscure. Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- ipc/sem.c | 1 - kernel/exit.c | 8 ++++++-- kernel/task_work.c | 1 - 3 files changed, 6 insertions(+), 4 deletions(-) diff --git a/ipc/sem.c b/ipc/sem.c index 84dff3df11a4..ae72b3cddc8d 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -282,7 +282,6 @@ static void sem_wait_array(struct sem_array *sma) sem = sma->sem_base + i; spin_unlock_wait(&sem->lock); } - smp_acquire__after_ctrl_dep(); } /* diff --git a/kernel/exit.c b/kernel/exit.c index 9e6e1356e6bb..0b40791b9e70 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -700,10 +700,14 @@ void do_exit(long code) exit_signals(tsk); /* sets PF_EXITING */ /* - * tsk->flags are checked in the futex code to protect against - * an exiting task cleaning up the robust pi futexes. + * Ensure that all new tsk->pi_lock acquisitions must observe + * PF_EXITING. Serializes against futex.c:attach_to_pi_owner(). */ smp_mb(); + /* + * Ensure that we must observe the pi_state in exit_mm() -> + * mm_release() -> exit_pi_state_list(). + */ raw_spin_unlock_wait(&tsk->pi_lock); if (unlikely(in_atomic())) { diff --git a/kernel/task_work.c b/kernel/task_work.c index 53fa971d000d..6ab4842b00e8 100644 --- a/kernel/task_work.c +++ b/kernel/task_work.c @@ -108,7 +108,6 @@ void task_work_run(void) * fail, but it can play with *work and other entries. */ raw_spin_unlock_wait(&task->pi_lock); - smp_mb(); do { next = work->next; -- 2.20.1