[PATCH 3/4] irq_work: Slightly simplify IRQ_WORK_PENDING clearing

Frederic Weisbecker
2019-11-08T16:09:31Z

Instead of fetching the value of flags and perform an xchg() to clear
a bit, just use atomic_fetch_andnot() that is more suitable to do that
job in one operation while keeping the full ordering.

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
---
kernel/irq_work.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/kernel/irq_work.c b/kernel/irq_work.c
index 255454a48346..49c53f80a13a 100644
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -34,7 +34,7 @@ static bool irq_work_claim(struct irq_work *work)
oflags = atomic_fetch_or(IRQ_WORK_CLAIMED, &work->flags);
/*
* If the work is already pending, no need to raise the IPI.
- * The pairing atomic_xchg() in irq_work_run() makes sure
+ * The pairing atomic_fetch_andnot() in irq_work_run() makes sure
* everything we did before is visible.
*/
if (oflags & IRQ_WORK_PENDING)
@@ -135,7 +135,6 @@ static void irq_work_run_list(struct llist_head *list)
{
struct irq_work *work, *tmp;
struct llist_node *llnode;
- int flags;

BUG_ON(!irqs_disabled());

@@ -144,6 +143,7 @@ static void irq_work_run_list(struct llist_head *list)

llnode = llist_del_all(list);
llist_for_each_entry_safe(work, tmp, llnode, llnode) {
+ int flags;
/*
* Clear the PENDING bit, after this point the @work
* can be re-used.
@@ -151,8 +151,7 @@ static void irq_work_run_list(struct llist_head *list)
* to claim that work don't rely on us to handle their data
* while we are in the middle of the func.
*/
- flags = atomic_read(&work->flags) & ~IRQ_WORK_PENDING;
- atomic_xchg(&work->flags, flags);
+ flags = atomic_fetch_andnot(IRQ_WORK_PENDING, &work->flags);

work->func(work);
/*
--
2.23.0