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authorPeter Zijlstra <peterz@infradead.org>2016-05-24 14:45:21 +0200
committerIngo Molnar <mingo@kernel.org>2016-06-14 11:55:15 +0200
commitbe3e7844980352756de4261b276ee2ba5be7a26b (patch)
tree977f32f488649a6c77dcec9190d36fddc3df6b69
parent726328d92a42b6d4b76078e2659f43067f82c4e8 (diff)
downloadlinux-be3e7844980352756de4261b276ee2ba5be7a26b.tar.bz2
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) <peterz@infradead.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--ipc/sem.c1
-rw-r--r--kernel/exit.c8
-rw-r--r--kernel/task_work.c1
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;