Re: [PATCH 0/4] (Was: lockdep trace from posix timers)
On 09/06, Peter Zijlstra wrote: > > Anyway, do you want me to take these patches through -tip? This would be great, thanks. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 0/4] (Was: lockdep trace from posix timers)
On 09/06, Peter Zijlstra wrote: Anyway, do you want me to take these patches through -tip? This would be great, thanks. Oleg. -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 0/4] (Was: lockdep trace from posix timers)
On Thu, 2012-09-06 at 20:01 +0200, Oleg Nesterov wrote: > Ping... Right, email backlog :-) > Peter, do you think you can do your make-it-lockless patch (hehe, I > think this is not possible ;) on top? Sure, I was trying to see if I could play games with the _cancel semantics that would satisfy the two callsites and be possible. No joy yet though. Anyway, do you want me to take these patches through -tip? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 0/4] (Was: lockdep trace from posix timers)
Ping...
Al, will you agree with these changes?
Peter, do you think you can do your make-it-lockless patch (hehe, I
think this is not possible ;) on top?
On 08/26, Oleg Nesterov wrote:
>
> On 08/24, Oleg Nesterov wrote:
> >
> > Peter, if you think it can work for you and if you agree with
> > the implementation I will be happy to send the patch.
>
> I think I should try anyway ;)
>
> To simplify the review, I attached the resulting code below.
>
> Changes:
>
> - Comments.
>
> - Not sure this is really better, but task_work_run()
> does not need to actually take pi_lock, unlock_wait
> is enough.
>
> However, in this case the dummy entry is better than
> the fake pointer.
>
> Oleg.
>
> #include
> #include
> #include
>
> static struct callback_head work_exited; /* all we need is ->next == NULL */
>
> int
> task_work_add(struct task_struct *task, struct callback_head *work, bool
> notify)
> {
> struct callback_head *head;
>
> do {
> head = ACCESS_ONCE(task->task_works);
> if (unlikely(head == _exited))
> return -ESRCH;
> work->next = head;
> } while (cmpxchg(>task_works, head, work) != head);
>
> if (notify)
> set_notify_resume(task);
> return 0;
> }
>
> struct callback_head *
> task_work_cancel(struct task_struct *task, task_work_func_t func)
> {
> struct callback_head **pprev = >task_works;
> struct callback_head *work = NULL;
> unsigned long flags;
> /*
>* If cmpxchg() fails we continue without updating pprev.
>* Either we raced with task_work_add() which added the
>* new entry before this work, we will find it again. Or
>* we raced with task_work_run(), *pprev == NULL/exited.
>*/
> raw_spin_lock_irqsave(>pi_lock, flags);
> while ((work = ACCESS_ONCE(*pprev))) {
> read_barrier_depends();
> if (work->func != func)
> pprev = >next;
> else if (cmpxchg(pprev, work, work->next) == work)
> break;
> }
> raw_spin_unlock_irqrestore(>pi_lock, flags);
>
> return work;
> }
>
> void task_work_run(void)
> {
> struct task_struct *task = current;
> struct callback_head *work, *head, *next;
>
> for (;;) {
> /*
>* work->func() can do task_work_add(), do not set
>* work_exited unless the list is empty.
>*/
> do {
> work = ACCESS_ONCE(task->task_works);
> head = !work && (task->flags & PF_EXITING) ?
> _exited : NULL;
> } while (cmpxchg(>task_works, work, head) != work);
>
> if (!work)
> break;
> /*
>* Synchronize with task_work_cancel(). It can't remove
>* the first entry == work, cmpxchg(task_works) should
>* fail, but it can play with *work and other entries.
>*/
> raw_spin_unlock_wait(>pi_lock);
> smp_mb();
>
> /* Reverse the list to run the works in fifo order */
> head = NULL;
> do {
> next = work->next;
> work->next = head;
> head = work;
> work = next;
> } while (work);
>
> work = head;
> do {
> next = work->next;
> work->func(work);
> work = next;
> cond_resched();
> } while (work);
> }
> }
--
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Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 0/4] (Was: lockdep trace from posix timers)
Ping...
Al, will you agree with these changes?
Peter, do you think you can do your make-it-lockless patch (hehe, I
think this is not possible ;) on top?
On 08/26, Oleg Nesterov wrote:
On 08/24, Oleg Nesterov wrote:
Peter, if you think it can work for you and if you agree with
the implementation I will be happy to send the patch.
I think I should try anyway ;)
To simplify the review, I attached the resulting code below.
Changes:
- Comments.
- Not sure this is really better, but task_work_run()
does not need to actually take pi_lock, unlock_wait
is enough.
However, in this case the dummy entry is better than
the fake pointer.
Oleg.
#include linux/spinlock.h
#include linux/task_work.h
#include linux/tracehook.h
static struct callback_head work_exited; /* all we need is -next == NULL */
int
task_work_add(struct task_struct *task, struct callback_head *work, bool
notify)
{
struct callback_head *head;
do {
head = ACCESS_ONCE(task-task_works);
if (unlikely(head == work_exited))
return -ESRCH;
work-next = head;
} while (cmpxchg(task-task_works, head, work) != head);
if (notify)
set_notify_resume(task);
return 0;
}
struct callback_head *
task_work_cancel(struct task_struct *task, task_work_func_t func)
{
struct callback_head **pprev = task-task_works;
struct callback_head *work = NULL;
unsigned long flags;
/*
* If cmpxchg() fails we continue without updating pprev.
* Either we raced with task_work_add() which added the
* new entry before this work, we will find it again. Or
* we raced with task_work_run(), *pprev == NULL/exited.
*/
raw_spin_lock_irqsave(task-pi_lock, flags);
while ((work = ACCESS_ONCE(*pprev))) {
read_barrier_depends();
if (work-func != func)
pprev = work-next;
else if (cmpxchg(pprev, work, work-next) == work)
break;
}
raw_spin_unlock_irqrestore(task-pi_lock, flags);
return work;
}
void task_work_run(void)
{
struct task_struct *task = current;
struct callback_head *work, *head, *next;
for (;;) {
/*
* work-func() can do task_work_add(), do not set
* work_exited unless the list is empty.
*/
do {
work = ACCESS_ONCE(task-task_works);
head = !work (task-flags PF_EXITING) ?
work_exited : NULL;
} while (cmpxchg(task-task_works, work, head) != work);
if (!work)
break;
/*
* Synchronize with task_work_cancel(). It can't remove
* the first entry == work, cmpxchg(task_works) should
* fail, but it can play with *work and other entries.
*/
raw_spin_unlock_wait(task-pi_lock);
smp_mb();
/* Reverse the list to run the works in fifo order */
head = NULL;
do {
next = work-next;
work-next = head;
head = work;
work = next;
} while (work);
work = head;
do {
next = work-next;
work-func(work);
work = next;
cond_resched();
} while (work);
}
}
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH 0/4] (Was: lockdep trace from posix timers)
On Thu, 2012-09-06 at 20:01 +0200, Oleg Nesterov wrote: Ping... Right, email backlog :-) Peter, do you think you can do your make-it-lockless patch (hehe, I think this is not possible ;) on top? Sure, I was trying to see if I could play games with the _cancel semantics that would satisfy the two callsites and be possible. No joy yet though. Anyway, do you want me to take these patches through -tip? -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[PATCH 0/4] (Was: lockdep trace from posix timers)
On 08/24, Oleg Nesterov wrote:
>
> Peter, if you think it can work for you and if you agree with
> the implementation I will be happy to send the patch.
I think I should try anyway ;)
To simplify the review, I attached the resulting code below.
Changes:
- Comments.
- Not sure this is really better, but task_work_run()
does not need to actually take pi_lock, unlock_wait
is enough.
However, in this case the dummy entry is better than
the fake pointer.
Oleg.
#include
#include
#include
static struct callback_head work_exited; /* all we need is ->next == NULL */
int
task_work_add(struct task_struct *task, struct callback_head *work, bool notify)
{
struct callback_head *head;
do {
head = ACCESS_ONCE(task->task_works);
if (unlikely(head == _exited))
return -ESRCH;
work->next = head;
} while (cmpxchg(>task_works, head, work) != head);
if (notify)
set_notify_resume(task);
return 0;
}
struct callback_head *
task_work_cancel(struct task_struct *task, task_work_func_t func)
{
struct callback_head **pprev = >task_works;
struct callback_head *work = NULL;
unsigned long flags;
/*
* If cmpxchg() fails we continue without updating pprev.
* Either we raced with task_work_add() which added the
* new entry before this work, we will find it again. Or
* we raced with task_work_run(), *pprev == NULL/exited.
*/
raw_spin_lock_irqsave(>pi_lock, flags);
while ((work = ACCESS_ONCE(*pprev))) {
read_barrier_depends();
if (work->func != func)
pprev = >next;
else if (cmpxchg(pprev, work, work->next) == work)
break;
}
raw_spin_unlock_irqrestore(>pi_lock, flags);
return work;
}
void task_work_run(void)
{
struct task_struct *task = current;
struct callback_head *work, *head, *next;
for (;;) {
/*
* work->func() can do task_work_add(), do not set
* work_exited unless the list is empty.
*/
do {
work = ACCESS_ONCE(task->task_works);
head = !work && (task->flags & PF_EXITING) ?
_exited : NULL;
} while (cmpxchg(>task_works, work, head) != work);
if (!work)
break;
/*
* Synchronize with task_work_cancel(). It can't remove
* the first entry == work, cmpxchg(task_works) should
* fail, but it can play with *work and other entries.
*/
raw_spin_unlock_wait(>pi_lock);
smp_mb();
/* Reverse the list to run the works in fifo order */
head = NULL;
do {
next = work->next;
work->next = head;
head = work;
work = next;
} while (work);
work = head;
do {
next = work->next;
work->func(work);
work = next;
cond_resched();
} while (work);
}
}
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[PATCH 0/4] (Was: lockdep trace from posix timers)
On 08/24, Oleg Nesterov wrote:
Peter, if you think it can work for you and if you agree with
the implementation I will be happy to send the patch.
I think I should try anyway ;)
To simplify the review, I attached the resulting code below.
Changes:
- Comments.
- Not sure this is really better, but task_work_run()
does not need to actually take pi_lock, unlock_wait
is enough.
However, in this case the dummy entry is better than
the fake pointer.
Oleg.
#include linux/spinlock.h
#include linux/task_work.h
#include linux/tracehook.h
static struct callback_head work_exited; /* all we need is -next == NULL */
int
task_work_add(struct task_struct *task, struct callback_head *work, bool notify)
{
struct callback_head *head;
do {
head = ACCESS_ONCE(task-task_works);
if (unlikely(head == work_exited))
return -ESRCH;
work-next = head;
} while (cmpxchg(task-task_works, head, work) != head);
if (notify)
set_notify_resume(task);
return 0;
}
struct callback_head *
task_work_cancel(struct task_struct *task, task_work_func_t func)
{
struct callback_head **pprev = task-task_works;
struct callback_head *work = NULL;
unsigned long flags;
/*
* If cmpxchg() fails we continue without updating pprev.
* Either we raced with task_work_add() which added the
* new entry before this work, we will find it again. Or
* we raced with task_work_run(), *pprev == NULL/exited.
*/
raw_spin_lock_irqsave(task-pi_lock, flags);
while ((work = ACCESS_ONCE(*pprev))) {
read_barrier_depends();
if (work-func != func)
pprev = work-next;
else if (cmpxchg(pprev, work, work-next) == work)
break;
}
raw_spin_unlock_irqrestore(task-pi_lock, flags);
return work;
}
void task_work_run(void)
{
struct task_struct *task = current;
struct callback_head *work, *head, *next;
for (;;) {
/*
* work-func() can do task_work_add(), do not set
* work_exited unless the list is empty.
*/
do {
work = ACCESS_ONCE(task-task_works);
head = !work (task-flags PF_EXITING) ?
work_exited : NULL;
} while (cmpxchg(task-task_works, work, head) != work);
if (!work)
break;
/*
* Synchronize with task_work_cancel(). It can't remove
* the first entry == work, cmpxchg(task_works) should
* fail, but it can play with *work and other entries.
*/
raw_spin_unlock_wait(task-pi_lock);
smp_mb();
/* Reverse the list to run the works in fifo order */
head = NULL;
do {
next = work-next;
work-next = head;
head = work;
work = next;
} while (work);
work = head;
do {
next = work-next;
work-func(work);
work = next;
cond_resched();
} while (work);
}
}
--
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the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
