Re: [PATCH tip/core/rcu 1/3] membarrier: Provide register expedited private command
From: Peter Zijlstra <peterz@infradead.org>
Date: 2017-10-05 12:13:22
Also in:
linux-arch, lkml
On Wed, Oct 04, 2017 at 02:37:53PM -0700, Paul E. McKenney wrote:
quoted hunk ↗ jump to hunk
diff --git a/arch/powerpc/kernel/membarrier.c b/arch/powerpc/kernel/membarrier.c new file mode 100644 index 000000000000..b0d79a5f5981 --- /dev/null +++ b/arch/powerpc/kernel/membarrier.c@@ -0,0 +1,45 @@
+void membarrier_arch_register_private_expedited(struct task_struct *p)
+{
+ struct task_struct *t;
+
+ if (get_nr_threads(p) == 1) {
+ set_thread_flag(TIF_MEMBARRIER_PRIVATE_EXPEDITED);
+ return;
+ }
+ /*
+ * Coherence of TIF_MEMBARRIER_PRIVATE_EXPEDITED against thread
+ * fork is protected by siglock.
+ */
+ spin_lock(&p->sighand->siglock);
+ for_each_thread(p, t)
+ set_ti_thread_flag(task_thread_info(t),
+ TIF_MEMBARRIER_PRIVATE_EXPEDITED);I'm not sure this works correctly vs CLONE_VM without CLONE_THREAD.
+ spin_unlock(&p->sighand->siglock); + /* + * Ensure all future scheduler executions will observe the new + * thread flag state for this process. + */ + synchronize_sched();
This relies on the flag being read inside rq->lock, right?
+}