Merge branch 'core/irq_work' of git://git.kernel.org/pub/scm/linux/kernel/git/frederi...

[~andy/linux] / kernel / irq_work.c

diff --git a/kernel/irq_work.c b/kernel/irq_work.c
index 1588e3b2871b9e28a68316f91ca418d44a75cba2..64eddd59ed83852262b5655a56e8ebb284dcb119 100644 (file)
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -34,15 +34,21 @@ static DEFINE_PER_CPU(struct llist_head, irq_work_list);
  */
 static bool irq_work_claim(struct irq_work *work)
 {
-       unsigned long flags, nflags;
+       unsigned long flags, oflags, nflags;
 
+       /*
+        * Start with our best wish as a premise but only trust any
+        * flag value after cmpxchg() result.
+        */
+       flags = work->flags & ~IRQ_WORK_PENDING;
        for (;;) {
-               flags = work->flags;
-               if (flags & IRQ_WORK_PENDING)
-                       return false;
                nflags = flags | IRQ_WORK_FLAGS;
-               if (cmpxchg(&work->flags, flags, nflags) == flags)
+               oflags = cmpxchg(&work->flags, flags, nflags);
+               if (oflags == flags)
                        break;
+               if (oflags & IRQ_WORK_PENDING)
+                       return false;
+               flags = oflags;
                cpu_relax();
        }
 
@@ -119,8 +125,11 @@ void irq_work_run(void)
                /*
                 * Clear the PENDING bit, after this point the @work
                 * can be re-used.
+                * Make it immediately visible so that other CPUs trying
+                * to claim that work don't rely on us to handle their data
+                * while we are in the middle of the func.
                 */
-               work->flags = IRQ_WORK_BUSY;
+               xchg(&work->flags, IRQ_WORK_BUSY);
                work->func(work);
                /*
                 * Clear the BUSY bit and return to the free state if