Re: [PATCH] Fix posix-cpu-timer breakage caused by stale p->last_ran value
On Thu, 01 Mar 2007 18:45:14 -0500
Chuck Ebbert <[EMAIL PROTECTED]> wrote:
> Thomas Gleixner wrote:
> > Problem description at:
> > http://bugzilla.kernel.org/show_bug.cgi?id=8048
> >
> > Commit b18ec80396834497933d77b81ec0918519f4e2a7
> > [PATCH] sched: improve migration accuracy
> > optimized the scheduler time calculations, but broke posix-cpu-timers.
> >
> > The problem is that the p->last_ran value is not updated after a context
> > switch. So a subsequent call to current_sched_time() calculates with a
> > stale p->last_ran value, i.e. accounts the full time, which the task was
> > scheduled away.
> >
> > Signed-off-by: Thomas Gleixner <[EMAIL PROTECTED]>
> >
> > Index: linux-2.6/kernel/sched.c
> > ===
> > --- linux-2.6.orig/kernel/sched.c
> > +++ linux-2.6/kernel/sched.c
> > @@ -3566,7 +3566,7 @@ switch_tasks:
> >
> > sched_info_switch(prev, next);
> > if (likely(prev != next)) {
> > - next->timestamp = now;
> > + next->timestamp = next->last_ran = now;
> > rq->nr_switches++;
> > rq->curr = next;
> > ++*switch_count;
> >
>
> Is this going to be merged or not??
It just hit mainline.
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Re: [PATCH] Fix posix-cpu-timer breakage caused by stale p->last_ran value
Thomas Gleixner wrote:
> Problem description at:
> http://bugzilla.kernel.org/show_bug.cgi?id=8048
>
> Commit b18ec80396834497933d77b81ec0918519f4e2a7
> [PATCH] sched: improve migration accuracy
> optimized the scheduler time calculations, but broke posix-cpu-timers.
>
> The problem is that the p->last_ran value is not updated after a context
> switch. So a subsequent call to current_sched_time() calculates with a
> stale p->last_ran value, i.e. accounts the full time, which the task was
> scheduled away.
>
> Signed-off-by: Thomas Gleixner <[EMAIL PROTECTED]>
>
> Index: linux-2.6/kernel/sched.c
> ===
> --- linux-2.6.orig/kernel/sched.c
> +++ linux-2.6/kernel/sched.c
> @@ -3566,7 +3566,7 @@ switch_tasks:
>
> sched_info_switch(prev, next);
> if (likely(prev != next)) {
> - next->timestamp = now;
> + next->timestamp = next->last_ran = now;
> rq->nr_switches++;
> rq->curr = next;
> ++*switch_count;
>
Is this going to be merged or not??
-
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Re: [PATCH] Fix posix-cpu-timer breakage caused by stale p-last_ran value
Thomas Gleixner wrote:
Problem description at:
http://bugzilla.kernel.org/show_bug.cgi?id=8048
Commit b18ec80396834497933d77b81ec0918519f4e2a7
[PATCH] sched: improve migration accuracy
optimized the scheduler time calculations, but broke posix-cpu-timers.
The problem is that the p-last_ran value is not updated after a context
switch. So a subsequent call to current_sched_time() calculates with a
stale p-last_ran value, i.e. accounts the full time, which the task was
scheduled away.
Signed-off-by: Thomas Gleixner [EMAIL PROTECTED]
Index: linux-2.6/kernel/sched.c
===
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -3566,7 +3566,7 @@ switch_tasks:
sched_info_switch(prev, next);
if (likely(prev != next)) {
- next-timestamp = now;
+ next-timestamp = next-last_ran = now;
rq-nr_switches++;
rq-curr = next;
++*switch_count;
Is this going to be merged or not??
-
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the body of a message to [EMAIL PROTECTED]
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Re: [PATCH] Fix posix-cpu-timer breakage caused by stale p-last_ran value
On Thu, 01 Mar 2007 18:45:14 -0500
Chuck Ebbert [EMAIL PROTECTED] wrote:
Thomas Gleixner wrote:
Problem description at:
http://bugzilla.kernel.org/show_bug.cgi?id=8048
Commit b18ec80396834497933d77b81ec0918519f4e2a7
[PATCH] sched: improve migration accuracy
optimized the scheduler time calculations, but broke posix-cpu-timers.
The problem is that the p-last_ran value is not updated after a context
switch. So a subsequent call to current_sched_time() calculates with a
stale p-last_ran value, i.e. accounts the full time, which the task was
scheduled away.
Signed-off-by: Thomas Gleixner [EMAIL PROTECTED]
Index: linux-2.6/kernel/sched.c
===
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -3566,7 +3566,7 @@ switch_tasks:
sched_info_switch(prev, next);
if (likely(prev != next)) {
- next-timestamp = now;
+ next-timestamp = next-last_ran = now;
rq-nr_switches++;
rq-curr = next;
++*switch_count;
Is this going to be merged or not??
It just hit mainline.
-
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to [EMAIL PROTECTED]
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Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Fix posix-cpu-timer breakage caused by stale p->last_ran value
Thomas Gleixner wrote:
Problem description at:
http://bugzilla.kernel.org/show_bug.cgi?id=8048
Commit b18ec80396834497933d77b81ec0918519f4e2a7
[PATCH] sched: improve migration accuracy
optimized the scheduler time calculations, but broke posix-cpu-timers.
The problem is that the p->last_ran value is not updated after a context
switch. So a subsequent call to current_sched_time() calculates with a
stale p->last_ran value, i.e. accounts the full time, which the task was
scheduled away.
Could you expand on the impact of this bug for non-kernel hackers? :-)
I'm currently testing 2.6.20-rt5. My app runs in SCHED_RR and just
blocks waiting for several signals. Since my app is the only SCHED_RR
process running on the system, I get the impression that I'm not
affected by this bug. Is that correct?
Signed-off-by: Thomas Gleixner <[EMAIL PROTECTED]>
Index: linux-2.6/kernel/sched.c
===
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -3566,7 +3566,7 @@ switch_tasks:
sched_info_switch(prev, next);
if (likely(prev != next)) {
- next->timestamp = now;
+ next->timestamp = next->last_ran = now;
rq->nr_switches++;
rq->curr = next;
++*switch_count;
Regards,
John
-
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Re: [PATCH] Fix posix-cpu-timer breakage caused by stale p->last_ran value
On Thu, 2007-02-22 at 01:33 +0100, Thomas Gleixner wrote: > Problem description at: > http://bugzilla.kernel.org/show_bug.cgi?id=8048 > > Commit b18ec80396834497933d77b81ec0918519f4e2a7 > [PATCH] sched: improve migration accuracy > optimized the scheduler time calculations, but broke posix-cpu-timers. > > The problem is that the p->last_ran value is not updated after a context > switch. So a subsequent call to current_sched_time() calculates with a > stale p->last_ran value, i.e. accounts the full time, which the task was > scheduled away. Oops, missed that. You could also remove the prev->last_ran assignment just above your addition, and turn this into a negative cost bugfix :) -Mike - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Fix posix-cpu-timer breakage caused by stale p-last_ran value
On Thu, 2007-02-22 at 01:33 +0100, Thomas Gleixner wrote: Problem description at: http://bugzilla.kernel.org/show_bug.cgi?id=8048 Commit b18ec80396834497933d77b81ec0918519f4e2a7 [PATCH] sched: improve migration accuracy optimized the scheduler time calculations, but broke posix-cpu-timers. The problem is that the p-last_ran value is not updated after a context switch. So a subsequent call to current_sched_time() calculates with a stale p-last_ran value, i.e. accounts the full time, which the task was scheduled away. Oops, missed that. You could also remove the prev-last_ran assignment just above your addition, and turn this into a negative cost bugfix :) -Mike - To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Fix posix-cpu-timer breakage caused by stale p-last_ran value
Thomas Gleixner wrote:
Problem description at:
http://bugzilla.kernel.org/show_bug.cgi?id=8048
Commit b18ec80396834497933d77b81ec0918519f4e2a7
[PATCH] sched: improve migration accuracy
optimized the scheduler time calculations, but broke posix-cpu-timers.
The problem is that the p-last_ran value is not updated after a context
switch. So a subsequent call to current_sched_time() calculates with a
stale p-last_ran value, i.e. accounts the full time, which the task was
scheduled away.
Could you expand on the impact of this bug for non-kernel hackers? :-)
I'm currently testing 2.6.20-rt5. My app runs in SCHED_RR and just
blocks waiting for several signals. Since my app is the only SCHED_RR
process running on the system, I get the impression that I'm not
affected by this bug. Is that correct?
Signed-off-by: Thomas Gleixner [EMAIL PROTECTED]
Index: linux-2.6/kernel/sched.c
===
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -3566,7 +3566,7 @@ switch_tasks:
sched_info_switch(prev, next);
if (likely(prev != next)) {
- next-timestamp = now;
+ next-timestamp = next-last_ran = now;
rq-nr_switches++;
rq-curr = next;
++*switch_count;
Regards,
John
-
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the body of a message to [EMAIL PROTECTED]
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Re: [PATCH] Fix posix-cpu-timer breakage caused by stale p->last_ran value
On Thu, 2007-02-22 at 08:46 +0100, Ingo Molnar wrote:
> * Thomas Gleixner <[EMAIL PROTECTED]> wrote:
>
> > The problem is that the p->last_ran value is not updated after a
> > context switch. So a subsequent call to current_sched_time()
> > calculates with a stale p->last_ran value, i.e. accounts the full
> > time, which the task was scheduled away.
> >
> > Signed-off-by: Thomas Gleixner <[EMAIL PROTECTED]>
>
> > sched_info_switch(prev, next);
> > if (likely(prev != next)) {
> > - next->timestamp = now;
> > + next->timestamp = next->last_ran = now;
>
> ouch! nice catch. Also for v2.6.20.2 i think. 2.6.19 should be
> unaffected.
Yes, was introduced in 2.6.20 and definitely should hit the stable tree.
tglx
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Re: [PATCH] Fix posix-cpu-timer breakage caused by stale p->last_ran value
* Thomas Gleixner <[EMAIL PROTECTED]> wrote:
> The problem is that the p->last_ran value is not updated after a
> context switch. So a subsequent call to current_sched_time()
> calculates with a stale p->last_ran value, i.e. accounts the full
> time, which the task was scheduled away.
>
> Signed-off-by: Thomas Gleixner <[EMAIL PROTECTED]>
> sched_info_switch(prev, next);
> if (likely(prev != next)) {
> - next->timestamp = now;
> + next->timestamp = next->last_ran = now;
ouch! nice catch. Also for v2.6.20.2 i think. 2.6.19 should be
unaffected.
Acked-by: Ingo Molnar <[EMAIL PROTECTED]>
Ingo
-
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[PATCH] Fix posix-cpu-timer breakage caused by stale p->last_ran value
Problem description at:
http://bugzilla.kernel.org/show_bug.cgi?id=8048
Commit b18ec80396834497933d77b81ec0918519f4e2a7
[PATCH] sched: improve migration accuracy
optimized the scheduler time calculations, but broke posix-cpu-timers.
The problem is that the p->last_ran value is not updated after a context
switch. So a subsequent call to current_sched_time() calculates with a
stale p->last_ran value, i.e. accounts the full time, which the task was
scheduled away.
Signed-off-by: Thomas Gleixner <[EMAIL PROTECTED]>
Index: linux-2.6/kernel/sched.c
===
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -3566,7 +3566,7 @@ switch_tasks:
sched_info_switch(prev, next);
if (likely(prev != next)) {
- next->timestamp = now;
+ next->timestamp = next->last_ran = now;
rq->nr_switches++;
rq->curr = next;
++*switch_count;
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[PATCH] Fix posix-cpu-timer breakage caused by stale p-last_ran value
Problem description at:
http://bugzilla.kernel.org/show_bug.cgi?id=8048
Commit b18ec80396834497933d77b81ec0918519f4e2a7
[PATCH] sched: improve migration accuracy
optimized the scheduler time calculations, but broke posix-cpu-timers.
The problem is that the p-last_ran value is not updated after a context
switch. So a subsequent call to current_sched_time() calculates with a
stale p-last_ran value, i.e. accounts the full time, which the task was
scheduled away.
Signed-off-by: Thomas Gleixner [EMAIL PROTECTED]
Index: linux-2.6/kernel/sched.c
===
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -3566,7 +3566,7 @@ switch_tasks:
sched_info_switch(prev, next);
if (likely(prev != next)) {
- next-timestamp = now;
+ next-timestamp = next-last_ran = now;
rq-nr_switches++;
rq-curr = next;
++*switch_count;
-
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Fix posix-cpu-timer breakage caused by stale p-last_ran value
* Thomas Gleixner [EMAIL PROTECTED] wrote:
The problem is that the p-last_ran value is not updated after a
context switch. So a subsequent call to current_sched_time()
calculates with a stale p-last_ran value, i.e. accounts the full
time, which the task was scheduled away.
Signed-off-by: Thomas Gleixner [EMAIL PROTECTED]
sched_info_switch(prev, next);
if (likely(prev != next)) {
- next-timestamp = now;
+ next-timestamp = next-last_ran = now;
ouch! nice catch. Also for v2.6.20.2 i think. 2.6.19 should be
unaffected.
Acked-by: Ingo Molnar [EMAIL PROTECTED]
Ingo
-
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Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] Fix posix-cpu-timer breakage caused by stale p-last_ran value
On Thu, 2007-02-22 at 08:46 +0100, Ingo Molnar wrote:
* Thomas Gleixner [EMAIL PROTECTED] wrote:
The problem is that the p-last_ran value is not updated after a
context switch. So a subsequent call to current_sched_time()
calculates with a stale p-last_ran value, i.e. accounts the full
time, which the task was scheduled away.
Signed-off-by: Thomas Gleixner [EMAIL PROTECTED]
sched_info_switch(prev, next);
if (likely(prev != next)) {
- next-timestamp = now;
+ next-timestamp = next-last_ran = now;
ouch! nice catch. Also for v2.6.20.2 i think. 2.6.19 should be
unaffected.
Yes, was introduced in 2.6.20 and definitely should hit the stable tree.
tglx
-
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the body of a message to [EMAIL PROTECTED]
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