* [RFC] jffs2: use cond_resched() instead of yield()
@ 2010-09-01 16:03 Wolfram Sang
2010-09-01 18:35 ` Artem Bityutskiy
2010-09-20 13:00 ` Artem Bityutskiy
0 siblings, 2 replies; 6+ messages in thread
From: Wolfram Sang @ 2010-09-01 16:03 UTC (permalink / raw)
To: linux-kernel; +Cc: Artem Bityutskiy, Ingo Molnar, linux-mtd, Wolfram Sang
yield() has different semantics meanwhile and even causes RT-kernels to
BUG. Replace the only appearance left in jffs2.
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Cc: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Cc: Ingo Molnar <mingo@elte.hu>
---
The aforementioned BUG() showed up in one of our customer's RT-projects. While
this could be handled by rearranging his thread-priorities, I wondered if such
a patch would be worthwhile, still. Reading through the material covering
yield() and related replacements, I believe this patch should be appropriate.
Please say if I missed some side-effects.
fs/jffs2/erase.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/fs/jffs2/erase.c b/fs/jffs2/erase.c
index abac961..e513f19 100644
--- a/fs/jffs2/erase.c
+++ b/fs/jffs2/erase.c
@@ -151,7 +151,7 @@ int jffs2_erase_pending_blocks(struct jffs2_sb_info *c, int count)
}
/* Be nice */
- yield();
+ cond_resched();
mutex_lock(&c->erase_free_sem);
spin_lock(&c->erase_completion_lock);
}
--
1.7.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [RFC] jffs2: use cond_resched() instead of yield()
2010-09-01 16:03 [RFC] jffs2: use cond_resched() instead of yield() Wolfram Sang
@ 2010-09-01 18:35 ` Artem Bityutskiy
2010-09-02 7:01 ` Joakim Tjernlund
2010-09-20 13:00 ` Artem Bityutskiy
1 sibling, 1 reply; 6+ messages in thread
From: Artem Bityutskiy @ 2010-09-01 18:35 UTC (permalink / raw)
To: Wolfram Sang
Cc: Artem Bityutskiy, Ingo Molnar, dwmw2, linux-mtd, linux-kernel
This 'yield()' was introduced by dwmw2, so he may have strong feelings
about it. CCed.
On Wed, 2010-09-01 at 18:03 +0200, Wolfram Sang wrote:
> yield() has different semantics meanwhile and even causes RT-kernels to
> BUG. Replace the only appearance left in jffs2.
>
> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
> Cc: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
> Cc: Ingo Molnar <mingo@elte.hu>
> ---
>
> The aforementioned BUG() showed up in one of our customer's RT-projects. While
> this could be handled by rearranging his thread-priorities, I wondered if such
> a patch would be worthwhile, still. Reading through the material covering
> yield() and related replacements, I believe this patch should be appropriate.
> Please say if I missed some side-effects.
>
> fs/jffs2/erase.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/fs/jffs2/erase.c b/fs/jffs2/erase.c
> index abac961..e513f19 100644
> --- a/fs/jffs2/erase.c
> +++ b/fs/jffs2/erase.c
> @@ -151,7 +151,7 @@ int jffs2_erase_pending_blocks(struct jffs2_sb_info *c, int count)
> }
>
> /* Be nice */
> - yield();
> + cond_resched();
> mutex_lock(&c->erase_free_sem);
> spin_lock(&c->erase_completion_lock);
> }
--
Best Regards,
Artem Bityutskiy (Битюцкий Артём)
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [RFC] jffs2: use cond_resched() instead of yield()
2010-09-01 18:35 ` Artem Bityutskiy
@ 2010-09-02 7:01 ` Joakim Tjernlund
2010-09-02 10:59 ` Artem Bityutskiy
0 siblings, 1 reply; 6+ messages in thread
From: Joakim Tjernlund @ 2010-09-02 7:01 UTC (permalink / raw)
To: dedekind1
Cc: Artem Bityutskiy, linux-kernel, Wolfram Sang, linux-mtd,
Ingo Molnar, dwmw2
>
> This 'yield()' was introduced by dwmw2, so he may have strong feelings
> about it. CCed.
Actually, it was introduced by me with commit fd5324909e410a3202c1b01bd507c2dfba58fca5 :
[JFFS2] Fix hanging close for /dev/mtd character device.
When pdflush is erasing lots of sectors, drivers calling
mtd->sync will hang until all blocks are erased. Be nicer.
Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
@@ -142,7 +142,7 @@ void jffs2_erase_pending_blocks(struct jffs2_sb_info *c, int count)
}
/* Be nice */
- cond_resched();
+ yield();
spin_lock(&c->erase_completion_lock);
}
At the time cond_resched() was a problem but now I don't know. The erasing
has moved to the GC thread and been somewhat reworked. I don't know if
it still needs yield(). Perhaps David can tell?
Jocke
>
> On Wed, 2010-09-01 at 18:03 +0200, Wolfram Sang wrote:
> > yield() has different semantics meanwhile and even causes RT-kernels to
> > BUG. Replace the only appearance left in jffs2.
> >
> > Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
> > Cc: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
> > Cc: Ingo Molnar <mingo@elte.hu>
> > ---
> >
> > The aforementioned BUG() showed up in one of our customer's RT-projects. While
> > this could be handled by rearranging his thread-priorities, I wondered if such
> > a patch would be worthwhile, still. Reading through the material covering
> > yield() and related replacements, I believe this patch should be appropriate.
> > Please say if I missed some side-effects.
> >
> > fs/jffs2/erase.c | 2 +-
> > 1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/fs/jffs2/erase.c b/fs/jffs2/erase.c
> > index abac961..e513f19 100644
> > --- a/fs/jffs2/erase.c
> > +++ b/fs/jffs2/erase.c
> > @@ -151,7 +151,7 @@ int jffs2_erase_pending_blocks(struct jffs2_sb_info *c, int count)
> > }
> >
> > /* Be nice */
> > - yield();
> > + cond_resched();
> > mutex_lock(&c->erase_free_sem);
> > spin_lock(&c->erase_completion_lock);
> > }
>
> --
> Best Regards,
> Artem Bityutskiy (Битюцкий Артём)
>
>
> ______________________________________________________
> Linux MTD discussion mailing list
> http://lists.infradead.org/mailman/listinfo/linux-mtd/
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [RFC] jffs2: use cond_resched() instead of yield()
2010-09-02 7:01 ` Joakim Tjernlund
@ 2010-09-02 10:59 ` Artem Bityutskiy
2010-09-02 13:52 ` Joakim Tjernlund
0 siblings, 1 reply; 6+ messages in thread
From: Artem Bityutskiy @ 2010-09-02 10:59 UTC (permalink / raw)
To: Joakim Tjernlund
Cc: Artem Bityutskiy, linux-kernel, Wolfram Sang, linux-mtd,
Ingo Molnar, dwmw2
On Thu, 2010-09-02 at 09:01 +0200, Joakim Tjernlund wrote:
> At the time cond_resched() was a problem but now I don't know. The erasing
> has moved to the GC thread and been somewhat reworked. I don't know if
> it still needs yield(). Perhaps David can tell?
I think 'yield()' is rather a hack than a real solution.
--
Best Regards,
Artem Bityutskiy (Битюцкий Артём)
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [RFC] jffs2: use cond_resched() instead of yield()
2010-09-02 10:59 ` Artem Bityutskiy
@ 2010-09-02 13:52 ` Joakim Tjernlund
0 siblings, 0 replies; 6+ messages in thread
From: Joakim Tjernlund @ 2010-09-02 13:52 UTC (permalink / raw)
To: dedekind1
Cc: Artem Bityutskiy, linux-kernel, Wolfram Sang, linux-mtd,
Ingo Molnar, dwmw2
Artem Bityutskiy <dedekind1@gmail.com> wrote on 2010/09/02 12:59:09:
>
> On Thu, 2010-09-02 at 09:01 +0200, Joakim Tjernlund wrote:
> > At the time cond_resched() was a problem but now I don't know. The erasing
> > has moved to the GC thread and been somewhat reworked. I don't know if
> > it still needs yield(). Perhaps David can tell?
>
> I think 'yield()' is rather a hack than a real solution.
Yes, the real fix is to move erasing to GC and that has been done now.
There is a good chance yield() can be removed without regression
but I am not sure nor do I have the time to test that.
Jocke
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [RFC] jffs2: use cond_resched() instead of yield()
2010-09-01 16:03 [RFC] jffs2: use cond_resched() instead of yield() Wolfram Sang
2010-09-01 18:35 ` Artem Bityutskiy
@ 2010-09-20 13:00 ` Artem Bityutskiy
1 sibling, 0 replies; 6+ messages in thread
From: Artem Bityutskiy @ 2010-09-20 13:00 UTC (permalink / raw)
To: Wolfram Sang; +Cc: Ingo Molnar, linux-mtd, linux-kernel
On Wed, 2010-09-01 at 18:03 +0200, Wolfram Sang wrote:
> yield() has different semantics meanwhile and even causes RT-kernels to
> BUG. Replace the only appearance left in jffs2.
>
> Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
> Cc: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
> Cc: Ingo Molnar <mingo@elte.hu>
FYI, I've pushed this patch to my l2-mtd-2.6.git tree, thanks.
--
Best Regards,
Artem Bityutskiy (Артём Битюцкий)
^ permalink raw reply [flat|nested] 6+ messages in thread
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2010-09-01 16:03 [RFC] jffs2: use cond_resched() instead of yield() Wolfram Sang
2010-09-01 18:35 ` Artem Bityutskiy
2010-09-02 7:01 ` Joakim Tjernlund
2010-09-02 10:59 ` Artem Bityutskiy
2010-09-02 13:52 ` Joakim Tjernlund
2010-09-20 13:00 ` Artem Bityutskiy
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