Mailing List Archive: [PATCH] [RFC]IRQ CORE: irq_work_queue function return value not used.

[PATCH] [RFC]IRQ CORE: irq_work_queue function return value not used.

anish198519851985 at gmail

Oct 31, 2012, 7:02 AM

Post #1 of 4 (72 views)

From: anish kumar <anish198519851985@gmail.com>

As no one is using the return value of irq_work_queue function
it is better to just make it void.

This patch is just a way to understand if there is some future
plan to use it but in any case please let me know the reason.
---
kernel/irq_work.c | 21 ++++++++++-----------
1 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/kernel/irq_work.c b/kernel/irq_work.c
index 1588e3b..4a9a44c 100644
--- a/kernel/irq_work.c
+++ b/kernel/irq_work.c
@@ -32,21 +32,21 @@ static DEFINE_PER_CPU(struct llist_head, irq_work_list);
/*
* Claim the entry so that no one else will poke at it.
*/
-static bool irq_work_claim(struct irq_work *work)
+static void irq_work_claim(struct irq_work *work)
{
unsigned long flags, nflags;

for (;;) {
flags = work->flags;
if (flags & IRQ_WORK_PENDING)
- return false;
+ return;
nflags = flags | IRQ_WORK_FLAGS;
if (cmpxchg(&work->flags, flags, nflags) == flags)
break;
cpu_relax();
}

- return true;
+ return;
}

void __weak arch_irq_work_raise(void)
@@ -79,15 +79,14 @@ static void __irq_work_queue(struct irq_work *work)
*
* Can be re-enqueued while the callback is still in progress.
*/
-bool irq_work_queue(struct irq_work *work)
+void irq_work_queue(struct irq_work *work)
{
- if (!irq_work_claim(work)) {
- /*
- * Already enqueued, can't do!
- */
- return false;
- }
-
+ /*
+ * This function either will claim the entry to queue
+ * the work or if the work is already queued and is in
+ * pending state then it will simply return.
+ */
+ irq_work_claim(work)
__irq_work_queue(work);
return true;
}
--
1.7.1

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RE: [PATCH] [RFC]IRQ CORE: irq_work_queue function return value not used. [ In reply to ]

ramakrishna.pallala at intel

Oct 31, 2012, 7:09 AM

Post #2 of 4 (77 views)

Permalink

> -bool irq_work_queue(struct irq_work *work)
> +void irq_work_queue(struct irq_work *work)
> {
> - if (!irq_work_claim(work)) {
> - /*
> - * Already enqueued, can't do!
> - */
> - return false;
> - }
> -
> + /*
> + * This function either will claim the entry to queue
> + * the work or if the work is already queued and is in
> + * pending state then it will simply return.
> + */
> + irq_work_claim(work)
> __irq_work_queue(work);
> return true;
> }
You can remove the last return statement.

Thanks,
Ram
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Re: [PATCH] [RFC]IRQ CORE: irq_work_queue function return value not used. [ In reply to ]

rostedt at goodmis

Oct 31, 2012, 7:15 AM

Post #3 of 4 (74 views)

Permalink

On Wed, 2012-10-31 at 23:02 +0900, anish kumar wrote:
> From: anish kumar <anish198519851985@gmail.com>
>
> As no one is using the return value of irq_work_queue function
> it is better to just make it void.
>
> This patch is just a way to understand if there is some future
> plan to use it but in any case please let me know the reason.
> ---
> kernel/irq_work.c | 21 ++++++++++-----------
> 1 files changed, 10 insertions(+), 11 deletions(-)
>
> diff --git a/kernel/irq_work.c b/kernel/irq_work.c
> index 1588e3b..4a9a44c 100644
> --- a/kernel/irq_work.c
> +++ b/kernel/irq_work.c
> @@ -32,21 +32,21 @@ static DEFINE_PER_CPU(struct llist_head, irq_work_list);
> /*
> * Claim the entry so that no one else will poke at it.
> */
> -static bool irq_work_claim(struct irq_work *work)
> +static void irq_work_claim(struct irq_work *work)
> {
> unsigned long flags, nflags;
>
> for (;;) {
> flags = work->flags;
> if (flags & IRQ_WORK_PENDING)
> - return false;
> + return;
> nflags = flags | IRQ_WORK_FLAGS;
> if (cmpxchg(&work->flags, flags, nflags) == flags)
> break;
> cpu_relax();
> }
>
> - return true;
> + return;
> }
>
> void __weak arch_irq_work_raise(void)
> @@ -79,15 +79,14 @@ static void __irq_work_queue(struct irq_work *work)
> *
> * Can be re-enqueued while the callback is still in progress.
> */
> -bool irq_work_queue(struct irq_work *work)
> +void irq_work_queue(struct irq_work *work)
> {
> - if (!irq_work_claim(work)) {
> - /*
> - * Already enqueued, can't do!
> - */
> - return false;
> - }
> -
> + /*
> + * This function either will claim the entry to queue
> + * the work or if the work is already queued and is in
> + * pending state then it will simply return.
> + */
> + irq_work_claim(work)

Um, no.

If the state was already pending, we will corrupt the llist node of the
work if we call irq_work_queue(). You must check the return value of
irq_work_claim() and return if it fails. You can not call
__irq_work_queue() if irq_work_claim() does not succeed.

The return value of irq_work_queue() can be ignored, but not
irq_work_claim().

-- Steve

> __irq_work_queue(work);
> return true;
> }

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Re: [PATCH] [RFC]IRQ CORE: irq_work_queue function return value not used. [ In reply to ]

anish198519851985 at gmail

Oct 31, 2012, 7:36 AM

Post #4 of 4 (74 views)

Permalink

On Wed, 2012-10-31 at 10:15 -0400, Steven Rostedt wrote:
> On Wed, 2012-10-31 at 23:02 +0900, anish kumar wrote:
> > From: anish kumar <anish198519851985@gmail.com>
> >
> > As no one is using the return value of irq_work_queue function
> > it is better to just make it void.
> >
> > This patch is just a way to understand if there is some future
> > plan to use it but in any case please let me know the reason.
> > ---
> > kernel/irq_work.c | 21 ++++++++++-----------
> > 1 files changed, 10 insertions(+), 11 deletions(-)
> >
> > diff --git a/kernel/irq_work.c b/kernel/irq_work.c
> > index 1588e3b..4a9a44c 100644
> > --- a/kernel/irq_work.c
> > +++ b/kernel/irq_work.c
> > @@ -32,21 +32,21 @@ static DEFINE_PER_CPU(struct llist_head, irq_work_list);
> > /*
> > * Claim the entry so that no one else will poke at it.
> > */
> > -static bool irq_work_claim(struct irq_work *work)
> > +static void irq_work_claim(struct irq_work *work)
> > {
> > unsigned long flags, nflags;
> >
> > for (;;) {
> > flags = work->flags;
> > if (flags & IRQ_WORK_PENDING)
> > - return false;
> > + return;
> > nflags = flags | IRQ_WORK_FLAGS;
> > if (cmpxchg(&work->flags, flags, nflags) == flags)
> > break;
> > cpu_relax();
> > }
> >
> > - return true;
> > + return;
> > }
> >
> > void __weak arch_irq_work_raise(void)
> > @@ -79,15 +79,14 @@ static void __irq_work_queue(struct irq_work *work)
> > *
> > * Can be re-enqueued while the callback is still in progress.
> > */
> > -bool irq_work_queue(struct irq_work *work)
> > +void irq_work_queue(struct irq_work *work)
> > {
> > - if (!irq_work_claim(work)) {
> > - /*
> > - * Already enqueued, can't do!
> > - */
> > - return false;
> > - }
> > -
> > + /*
> > + * This function either will claim the entry to queue
> > + * the work or if the work is already queued and is in
> > + * pending state then it will simply return.
> > + */
> > + irq_work_claim(work)
>
> Um, no.
>
> If the state was already pending, we will corrupt the llist node of the
> work if we call irq_work_queue(). You must check the return value of
> irq_work_claim() and return if it fails. You can not call
> __irq_work_queue() if irq_work_claim() does not succeed.
>
> The return value of irq_work_queue() can be ignored, but not
> irq_work_claim().
Oh I didn't see that logic properly and rightly pointed out by you, we
should _just_ return instead of queuing the work if the state was
already pending.
>
> -- Steve
>
> > __irq_work_queue(work);
> > return true;
> > }
>
>

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