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irq_work: Slightly simplify IRQ_WORK_PENDING clearing

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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: 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>
Link: https://lkml.kernel.org/r/20191108160858.31665-4-frederic@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Frederic Weisbecker 2019-11-08 17:08:57 +01:00 committed by Ingo Molnar
parent 25269871db
commit feb4a51323
1 changed files with 3 additions and 4 deletions
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7
kernel/irq_work.c
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@ -34,7 +34,7 @@ static bool irq_work_claim(struct irq_work *work)
oflags = atomic_fetch_or(IRQ_WORK_CLAIMED, &work->flags); oflags = atomic_fetch_or(IRQ_WORK_CLAIMED, &work->flags);
/* /*
* If the work is already pending, no need to raise the IPI. * 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. * everything we did before is visible.
*/ */
if (oflags & IRQ_WORK_PENDING) 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 irq_work *work, *tmp;
struct llist_node *llnode; struct llist_node *llnode;
int flags;
BUG_ON(!irqs_disabled()); BUG_ON(!irqs_disabled());
@ -144,6 +143,7 @@ static void irq_work_run_list(struct llist_head *list)
llnode = llist_del_all(list); llnode = llist_del_all(list);
llist_for_each_entry_safe(work, tmp, llnode, llnode) { llist_for_each_entry_safe(work, tmp, llnode, llnode) {
int flags;
/* /*
* Clear the PENDING bit, after this point the @work * Clear the PENDING bit, after this point the @work
* can be re-used. * 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 * to claim that work don't rely on us to handle their data
* while we are in the middle of the func. * while we are in the middle of the func.
*/ */
flags = atomic_read(&work->flags) & ~IRQ_WORK_PENDING; flags = atomic_fetch_andnot(IRQ_WORK_PENDING, &work->flags);
atomic_xchg(&work->flags, flags);
work->func(work); work->func(work);
/* /*