[PATCH] irq_poll: Remove redundant barrier when using clear_bit_unlock()

[PATCH] irq_poll: Remove redundant barrier when using clear_bit_unlock()

[Davidlohr Bueso]

... as the call obviously already implies unlock/RC semantics,
therefore lets get rid of the superfluous smp_mb calls.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
---
 lib/irq_poll.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/lib/irq_poll.c b/lib/irq_poll.c
index 836f7db4e548..2a6ae2720ccb 100644
--- a/lib/irq_poll.c
+++ b/lib/irq_poll.c
@@ -50,7 +50,6 @@ EXPORT_SYMBOL(irq_poll_sched);
 static void __irq_poll_complete(struct irq_poll *iop)
 {
 	list_del(&iop->list);
-	smp_mb__before_atomic();
 	clear_bit_unlock(IRQ_POLL_F_SCHED, &iop->state);
 }
 
@@ -161,7 +160,6 @@ EXPORT_SYMBOL(irq_poll_disable);
 void irq_poll_enable(struct irq_poll *iop)
 {
 	BUG_ON(!test_bit(IRQ_POLL_F_SCHED, &iop->state));
-	smp_mb__before_atomic();
 	clear_bit_unlock(IRQ_POLL_F_SCHED, &iop->state);
 }
 EXPORT_SYMBOL(irq_poll_enable);
-- 
2.8.1

Re: [PATCH] irq_poll: Remove redundant barrier when using clear_bit_unlock()

[Bart Van Assche]

On 04/16/2016 01:55 PM, Davidlohr Bueso wrote:
> ... as the call obviously already implies unlock/RC semantics,
> therefore lets get rid of the superfluous smp_mb calls.

Hello Davidlohr,

Are you sure that this patch has been sent to the right person? I have 
helped to review a change in this code but I'm not the maintainer of 
this code.

Thanks,

Bart.

Re: [PATCH] irq_poll: Remove redundant barrier when using clear_bit_unlock()

[Davidlohr Bueso]

On Tue, 19 Apr 2016, Bart Van Assche wrote:

>On 04/16/2016 01:55 PM, Davidlohr Bueso wrote:
>>... as the call obviously already implies unlock/RC semantics,
>>therefore lets get rid of the superfluous smp_mb calls.
>
>Hello Davidlohr,
>
>Are you sure that this patch has been sent to the right person? I have 
>helped to review a change in this code but I'm not the maintainer of 
>this code.

Ah, adding Andrew and Ingo, not sure who is responsible for these bits.

Thanks,
Davidlohr

Re: [PATCH] irq_poll: Remove redundant barrier when using clear_bit_unlock()

[Bart Van Assche]

On 04/19/2016 09:23 PM, Davidlohr Bueso wrote:
> On Tue, 19 Apr 2016, Bart Van Assche wrote:
>
>> On 04/16/2016 01:55 PM, Davidlohr Bueso wrote:
>>> ... as the call obviously already implies unlock/RC semantics,
>>> therefore lets get rid of the superfluous smp_mb calls.
>>
>> Hello Davidlohr,
>>
>> Are you sure that this patch has been sent to the right person? I have
>> helped to review a change in this code but I'm not the maintainer of
>> this code.
>
> Ah, adding Andrew and Ingo, not sure who is responsible for these bits.

Please also CC Jens Axboe and Christoph Hellwig. Jens is the original 
author of this code. See also "block: add blk-iopoll, a NAPI like 
approach for block devices" 
(https://groups.google.com/forum/#!topic/linux.kernel/aMhcMrYaXC8).

Bart.