* [PATCH 1/3] scsi: drop unlikely behind BUG_ON()
@ 2015-10-04 6:18 Geliang Tang
2015-10-04 6:18 ` [PATCH 2/3] sched/core: " Geliang Tang
2015-10-04 14:33 ` Bart Van Assche
0 siblings, 2 replies; 18+ messages in thread
From: Geliang Tang @ 2015-10-04 6:18 UTC (permalink / raw)
To: James E.J. Bottomley; +Cc: Geliang Tang, linux-scsi, linux-kernel
BUG_ON() already contain an unlikely compiler flag. Drop it.
Signed-off-by: Geliang Tang <geliangtang@163.com>
---
drivers/scsi/scsi_lib.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index f570b48..3b5faab 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1164,8 +1164,8 @@ int scsi_init_io(struct scsi_cmnd *cmd)
count = blk_rq_map_integrity_sg(rq->q, rq->bio,
prot_sdb->table.sgl);
- BUG_ON(unlikely(count > ivecs));
- BUG_ON(unlikely(count > queue_max_integrity_segments(rq->q)));
+ BUG_ON(count > ivecs);
+ BUG_ON(count > queue_max_integrity_segments(rq->q));
cmd->prot_sdb = prot_sdb;
cmd->prot_sdb->table.nents = count;
--
2.5.0
^ permalink raw reply related [flat|nested] 18+ messages in thread
* [PATCH 2/3] sched/core: drop unlikely behind BUG_ON()
2015-10-04 6:18 [PATCH 1/3] scsi: drop unlikely behind BUG_ON() Geliang Tang
@ 2015-10-04 6:18 ` Geliang Tang
2015-10-04 6:18 ` Geliang Tang
2015-10-04 14:33 ` Bart Van Assche
1 sibling, 1 reply; 18+ messages in thread
From: Geliang Tang @ 2015-10-04 6:18 UTC (permalink / raw)
To: Ingo Molnar, Peter Zijlstra; +Cc: Geliang Tang, linux-kernel
BUG_ON() already contain an unlikely compiler flag. Drop it.
Signed-off-by: Geliang Tang <geliangtang@163.com>
---
kernel/sched/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index fe81929..a3518789 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2947,7 +2947,7 @@ static noinline void __schedule_bug(struct task_struct *prev)
static inline void schedule_debug(struct task_struct *prev)
{
#ifdef CONFIG_SCHED_STACK_END_CHECK
- BUG_ON(unlikely(task_stack_end_corrupted(prev)));
+ BUG_ON(task_stack_end_corrupted(prev));
#endif
/*
* Test if we are atomic. Since do_exit() needs to call into
--
2.5.0
^ permalink raw reply related [flat|nested] 18+ messages in thread
* [PATCH 3/3] mm/nommu: drop unlikely behind BUG_ON()
2015-10-04 6:18 ` [PATCH 2/3] sched/core: " Geliang Tang
@ 2015-10-04 6:18 ` Geliang Tang
0 siblings, 0 replies; 18+ messages in thread
From: Geliang Tang @ 2015-10-04 6:18 UTC (permalink / raw)
To: Andrew Morton, Kirill A. Shutemov, Hugh Dickins,
Peter Zijlstra (Intel),
Andrea Arcangeli, Davidlohr Bueso, Joonsoo Kim, Arnd Bergmann,
Paul Gortmaker, Leon Romanovsky, Oleg Nesterov
Cc: Geliang Tang, linux-mm, linux-kernel
BUG_ON() already contain an unlikely compiler flag. Drop it.
Signed-off-by: Geliang Tang <geliangtang@163.com>
---
mm/nommu.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/mm/nommu.c b/mm/nommu.c
index 1e0f168..92be862 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -578,16 +578,16 @@ static noinline void validate_nommu_regions(void)
return;
last = rb_entry(lastp, struct vm_region, vm_rb);
- BUG_ON(unlikely(last->vm_end <= last->vm_start));
- BUG_ON(unlikely(last->vm_top < last->vm_end));
+ BUG_ON(last->vm_end <= last->vm_start);
+ BUG_ON(last->vm_top < last->vm_end);
while ((p = rb_next(lastp))) {
region = rb_entry(p, struct vm_region, vm_rb);
last = rb_entry(lastp, struct vm_region, vm_rb);
- BUG_ON(unlikely(region->vm_end <= region->vm_start));
- BUG_ON(unlikely(region->vm_top < region->vm_end));
- BUG_ON(unlikely(region->vm_start < last->vm_top));
+ BUG_ON(region->vm_end <= region->vm_start);
+ BUG_ON(region->vm_top < region->vm_end);
+ BUG_ON(region->vm_start < last->vm_top);
lastp = p;
}
--
2.5.0
^ permalink raw reply related [flat|nested] 18+ messages in thread
* [PATCH 3/3] mm/nommu: drop unlikely behind BUG_ON()
@ 2015-10-04 6:18 ` Geliang Tang
0 siblings, 0 replies; 18+ messages in thread
From: Geliang Tang @ 2015-10-04 6:18 UTC (permalink / raw)
To: Andrew Morton, Kirill A. Shutemov, Hugh Dickins,
Peter Zijlstra (Intel),
Andrea Arcangeli, Davidlohr Bueso, Joonsoo Kim, Arnd Bergmann,
Paul Gortmaker, Leon Romanovsky, Oleg Nesterov
Cc: Geliang Tang, linux-mm, linux-kernel
BUG_ON() already contain an unlikely compiler flag. Drop it.
Signed-off-by: Geliang Tang <geliangtang@163.com>
---
mm/nommu.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/mm/nommu.c b/mm/nommu.c
index 1e0f168..92be862 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -578,16 +578,16 @@ static noinline void validate_nommu_regions(void)
return;
last = rb_entry(lastp, struct vm_region, vm_rb);
- BUG_ON(unlikely(last->vm_end <= last->vm_start));
- BUG_ON(unlikely(last->vm_top < last->vm_end));
+ BUG_ON(last->vm_end <= last->vm_start);
+ BUG_ON(last->vm_top < last->vm_end);
while ((p = rb_next(lastp))) {
region = rb_entry(p, struct vm_region, vm_rb);
last = rb_entry(lastp, struct vm_region, vm_rb);
- BUG_ON(unlikely(region->vm_end <= region->vm_start));
- BUG_ON(unlikely(region->vm_top < region->vm_end));
- BUG_ON(unlikely(region->vm_start < last->vm_top));
+ BUG_ON(region->vm_end <= region->vm_start);
+ BUG_ON(region->vm_top < region->vm_end);
+ BUG_ON(region->vm_start < last->vm_top);
lastp = p;
}
--
2.5.0
--
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^ permalink raw reply related [flat|nested] 18+ messages in thread
* Re: [PATCH 3/3] mm/nommu: drop unlikely behind BUG_ON()
2015-10-04 6:18 ` Geliang Tang
@ 2015-10-04 11:02 ` Leon Romanovsky
-1 siblings, 0 replies; 18+ messages in thread
From: Leon Romanovsky @ 2015-10-04 11:02 UTC (permalink / raw)
To: Geliang Tang
Cc: Andrew Morton, Kirill A. Shutemov, Hugh Dickins,
Peter Zijlstra (Intel),
Andrea Arcangeli, Davidlohr Bueso, Joonsoo Kim, Arnd Bergmann,
Paul Gortmaker, Oleg Nesterov, Linux-MM, linux-kernel
On Sun, Oct 4, 2015 at 9:18 AM, Geliang Tang <geliangtang@163.com> wrote:
> BUG_ON() already contain an unlikely compiler flag. Drop it.
It is not the case if CONFIG_BUG and HAVE_ARCH_BUG_ON are not set.
>
> Signed-off-by: Geliang Tang <geliangtang@163.com>
> ---
> mm/nommu.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/mm/nommu.c b/mm/nommu.c
> index 1e0f168..92be862 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -578,16 +578,16 @@ static noinline void validate_nommu_regions(void)
> return;
>
> last = rb_entry(lastp, struct vm_region, vm_rb);
> - BUG_ON(unlikely(last->vm_end <= last->vm_start));
> - BUG_ON(unlikely(last->vm_top < last->vm_end));
> + BUG_ON(last->vm_end <= last->vm_start);
> + BUG_ON(last->vm_top < last->vm_end);
>
> while ((p = rb_next(lastp))) {
> region = rb_entry(p, struct vm_region, vm_rb);
> last = rb_entry(lastp, struct vm_region, vm_rb);
>
> - BUG_ON(unlikely(region->vm_end <= region->vm_start));
> - BUG_ON(unlikely(region->vm_top < region->vm_end));
> - BUG_ON(unlikely(region->vm_start < last->vm_top));
> + BUG_ON(region->vm_end <= region->vm_start);
> + BUG_ON(region->vm_top < region->vm_end);
> + BUG_ON(region->vm_start < last->vm_top);
>
> lastp = p;
> }
> --
> 2.5.0
>
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
--
Leon Romanovsky | Independent Linux Consultant
www.leon.nu | leon@leon.nu
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 3/3] mm/nommu: drop unlikely behind BUG_ON()
@ 2015-10-04 11:02 ` Leon Romanovsky
0 siblings, 0 replies; 18+ messages in thread
From: Leon Romanovsky @ 2015-10-04 11:02 UTC (permalink / raw)
To: Geliang Tang
Cc: Andrew Morton, Kirill A. Shutemov, Hugh Dickins,
Peter Zijlstra (Intel),
Andrea Arcangeli, Davidlohr Bueso, Joonsoo Kim, Arnd Bergmann,
Paul Gortmaker, Oleg Nesterov, Linux-MM, linux-kernel
On Sun, Oct 4, 2015 at 9:18 AM, Geliang Tang <geliangtang@163.com> wrote:
> BUG_ON() already contain an unlikely compiler flag. Drop it.
It is not the case if CONFIG_BUG and HAVE_ARCH_BUG_ON are not set.
>
> Signed-off-by: Geliang Tang <geliangtang@163.com>
> ---
> mm/nommu.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/mm/nommu.c b/mm/nommu.c
> index 1e0f168..92be862 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -578,16 +578,16 @@ static noinline void validate_nommu_regions(void)
> return;
>
> last = rb_entry(lastp, struct vm_region, vm_rb);
> - BUG_ON(unlikely(last->vm_end <= last->vm_start));
> - BUG_ON(unlikely(last->vm_top < last->vm_end));
> + BUG_ON(last->vm_end <= last->vm_start);
> + BUG_ON(last->vm_top < last->vm_end);
>
> while ((p = rb_next(lastp))) {
> region = rb_entry(p, struct vm_region, vm_rb);
> last = rb_entry(lastp, struct vm_region, vm_rb);
>
> - BUG_ON(unlikely(region->vm_end <= region->vm_start));
> - BUG_ON(unlikely(region->vm_top < region->vm_end));
> - BUG_ON(unlikely(region->vm_start < last->vm_top));
> + BUG_ON(region->vm_end <= region->vm_start);
> + BUG_ON(region->vm_top < region->vm_end);
> + BUG_ON(region->vm_start < last->vm_top);
>
> lastp = p;
> }
> --
> 2.5.0
>
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
--
Leon Romanovsky | Independent Linux Consultant
www.leon.nu | leon@leon.nu
--
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^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 1/3] scsi: drop unlikely behind BUG_ON()
2015-10-04 6:18 [PATCH 1/3] scsi: drop unlikely behind BUG_ON() Geliang Tang
@ 2015-10-04 14:33 ` Bart Van Assche
2015-10-04 14:33 ` Bart Van Assche
1 sibling, 0 replies; 18+ messages in thread
From: Bart Van Assche @ 2015-10-04 14:33 UTC (permalink / raw)
To: Geliang Tang, James E.J. Bottomley; +Cc: linux-scsi, linux-kernel
On 10/03/15 23:18, Geliang Tang wrote:
> BUG_ON() already contain an unlikely compiler flag. Drop it.
>
> Signed-off-by: Geliang Tang <geliangtang@163.com>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 1/3] scsi: drop unlikely behind BUG_ON()
@ 2015-10-04 14:33 ` Bart Van Assche
0 siblings, 0 replies; 18+ messages in thread
From: Bart Van Assche @ 2015-10-04 14:33 UTC (permalink / raw)
To: Geliang Tang, James E.J. Bottomley; +Cc: linux-scsi, linux-kernel
On 10/03/15 23:18, Geliang Tang wrote:
> BUG_ON() already contain an unlikely compiler flag. Drop it.
>
> Signed-off-by: Geliang Tang <geliangtang@163.com>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 3/3] mm/nommu: drop unlikely behind BUG_ON()
2015-10-04 6:18 ` Geliang Tang
@ 2015-10-05 1:50 ` Davidlohr Bueso
-1 siblings, 0 replies; 18+ messages in thread
From: Davidlohr Bueso @ 2015-10-05 1:50 UTC (permalink / raw)
To: Geliang Tang
Cc: Andrew Morton, Kirill A. Shutemov, Hugh Dickins,
Peter Zijlstra (Intel),
Andrea Arcangeli, Joonsoo Kim, Arnd Bergmann, Paul Gortmaker,
Leon Romanovsky, Oleg Nesterov, linux-mm, linux-kernel
On Sun, 04 Oct 2015, Geliang Tang wrote:
>BUG_ON() already contain an unlikely compiler flag. Drop it.
>
>Signed-off-by: Geliang Tang <geliangtang@163.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
... but I believe you do have some left:
drivers/scsi/scsi_lib.c: BUG_ON(unlikely(count > ivecs));
drivers/scsi/scsi_lib.c: BUG_ON(unlikely(count > queue_max_integrity_segments(rq->q)));
kernel/sched/core.c: BUG_ON(unlikely(task_stack_end_corrupted(prev)));
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 3/3] mm/nommu: drop unlikely behind BUG_ON()
@ 2015-10-05 1:50 ` Davidlohr Bueso
0 siblings, 0 replies; 18+ messages in thread
From: Davidlohr Bueso @ 2015-10-05 1:50 UTC (permalink / raw)
To: Geliang Tang
Cc: Andrew Morton, Kirill A. Shutemov, Hugh Dickins,
Peter Zijlstra (Intel),
Andrea Arcangeli, Joonsoo Kim, Arnd Bergmann, Paul Gortmaker,
Leon Romanovsky, Oleg Nesterov, linux-mm, linux-kernel
On Sun, 04 Oct 2015, Geliang Tang wrote:
>BUG_ON() already contain an unlikely compiler flag. Drop it.
>
>Signed-off-by: Geliang Tang <geliangtang@163.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
... but I believe you do have some left:
drivers/scsi/scsi_lib.c: BUG_ON(unlikely(count > ivecs));
drivers/scsi/scsi_lib.c: BUG_ON(unlikely(count > queue_max_integrity_segments(rq->q)));
kernel/sched/core.c: BUG_ON(unlikely(task_stack_end_corrupted(prev)));
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 3/3] mm/nommu: drop unlikely behind BUG_ON()
2015-10-04 11:02 ` Leon Romanovsky
@ 2015-10-05 2:04 ` Davidlohr Bueso
-1 siblings, 0 replies; 18+ messages in thread
From: Davidlohr Bueso @ 2015-10-05 2:04 UTC (permalink / raw)
To: Leon Romanovsky
Cc: Geliang Tang, Andrew Morton, Kirill A. Shutemov, Hugh Dickins,
Peter Zijlstra (Intel),
Andrea Arcangeli, Joonsoo Kim, Arnd Bergmann, Paul Gortmaker,
Oleg Nesterov, Linux-MM, linux-kernel
On Sun, 04 Oct 2015, Leon Romanovsky wrote:
>On Sun, Oct 4, 2015 at 9:18 AM, Geliang Tang <geliangtang@163.com> wrote:
>> BUG_ON() already contain an unlikely compiler flag. Drop it.
>It is not the case if CONFIG_BUG and HAVE_ARCH_BUG_ON are not set.
Yeah, but that's like the 1% of the cases -- and those probably don't even care
about the branch prediction (I could be wrong). So overall I like getting rid of
explicit BUG_ON(unlikely(... calls. In fact there's a _reason_ why there are so
few of them in the kernel.
Thanks,
Davidlohr
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 3/3] mm/nommu: drop unlikely behind BUG_ON()
@ 2015-10-05 2:04 ` Davidlohr Bueso
0 siblings, 0 replies; 18+ messages in thread
From: Davidlohr Bueso @ 2015-10-05 2:04 UTC (permalink / raw)
To: Leon Romanovsky
Cc: Geliang Tang, Andrew Morton, Kirill A. Shutemov, Hugh Dickins,
Peter Zijlstra (Intel),
Andrea Arcangeli, Joonsoo Kim, Arnd Bergmann, Paul Gortmaker,
Oleg Nesterov, Linux-MM, linux-kernel
On Sun, 04 Oct 2015, Leon Romanovsky wrote:
>On Sun, Oct 4, 2015 at 9:18 AM, Geliang Tang <geliangtang@163.com> wrote:
>> BUG_ON() already contain an unlikely compiler flag. Drop it.
>It is not the case if CONFIG_BUG and HAVE_ARCH_BUG_ON are not set.
Yeah, but that's like the 1% of the cases -- and those probably don't even care
about the branch prediction (I could be wrong). So overall I like getting rid of
explicit BUG_ON(unlikely(... calls. In fact there's a _reason_ why there are so
few of them in the kernel.
Thanks,
Davidlohr
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 3/3] mm/nommu: drop unlikely behind BUG_ON()
2015-10-05 1:50 ` Davidlohr Bueso
@ 2015-10-05 2:30 ` Geliang Tang
-1 siblings, 0 replies; 18+ messages in thread
From: Geliang Tang @ 2015-10-05 2:30 UTC (permalink / raw)
To: Davidlohr Bueso
Cc: Andrew Morton, Kirill A. Shutemov, Hugh Dickins,
Peter Zij lstra (Intel),
Andrea Arcangeli, Joonsoo Kim, Arnd Bergmann, Paul Gortmaker,
Leon Romanovsky, Oleg Nesterov, linux-mm, linux-kernel
On Sun, Oct 04, 2015 at 06:50:55PM -0700, Davidlohr Bueso wrote:
> On Sun, 04 Oct 2015, Geliang Tang wrote:
>
> >BUG_ON() already contain an unlikely compiler flag. Drop it.
> >
> >Signed-off-by: Geliang Tang <geliangtang@163.com>
>
> Acked-by: Davidlohr Bueso <dave@stgolabs.net>
>
> ... but I believe you do have some left:
>
> drivers/scsi/scsi_lib.c: BUG_ON(unlikely(count > ivecs));
> drivers/scsi/scsi_lib.c: BUG_ON(unlikely(count > queue_max_integrity_segments(rq->q)));
> kernel/sched/core.c: BUG_ON(unlikely(task_stack_end_corrupted(prev)));
Thanks for your review, the left have been sended out already in two other patches.
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 3/3] mm/nommu: drop unlikely behind BUG_ON()
@ 2015-10-05 2:30 ` Geliang Tang
0 siblings, 0 replies; 18+ messages in thread
From: Geliang Tang @ 2015-10-05 2:30 UTC (permalink / raw)
To: Davidlohr Bueso
Cc: Andrew Morton, Kirill A. Shutemov, Hugh Dickins,
Peter Zij lstra (Intel),
Andrea Arcangeli, Joonsoo Kim, Arnd Bergmann, Paul Gortmaker,
Leon Romanovsky, Oleg Nesterov, linux-mm, linux-kernel
On Sun, Oct 04, 2015 at 06:50:55PM -0700, Davidlohr Bueso wrote:
> On Sun, 04 Oct 2015, Geliang Tang wrote:
>
> >BUG_ON() already contain an unlikely compiler flag. Drop it.
> >
> >Signed-off-by: Geliang Tang <geliangtang@163.com>
>
> Acked-by: Davidlohr Bueso <dave@stgolabs.net>
>
> ... but I believe you do have some left:
>
> drivers/scsi/scsi_lib.c: BUG_ON(unlikely(count > ivecs));
> drivers/scsi/scsi_lib.c: BUG_ON(unlikely(count > queue_max_integrity_segments(rq->q)));
> kernel/sched/core.c: BUG_ON(unlikely(task_stack_end_corrupted(prev)));
Thanks for your review, the left have been sended out already in two other patches.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 3/3] mm/nommu: drop unlikely behind BUG_ON()
2015-10-05 2:30 ` Geliang Tang
@ 2015-10-05 3:37 ` Davidlohr Bueso
-1 siblings, 0 replies; 18+ messages in thread
From: Davidlohr Bueso @ 2015-10-05 3:37 UTC (permalink / raw)
To: Geliang Tang
Cc: Andrew Morton, Kirill A. Shutemov, Hugh Dickins,
Peter Zij lstra (Intel),
Andrea Arcangeli, Joonsoo Kim, Arnd Bergmann, Paul Gortmaker,
Leon Romanovsky, Oleg Nesterov, linux-mm, linux-kernel
On Mon, 05 Oct 2015, Geliang Tang wrote:
>On Sun, Oct 04, 2015 at 06:50:55PM -0700, Davidlohr Bueso wrote:
>> On Sun, 04 Oct 2015, Geliang Tang wrote:
>>
>> >BUG_ON() already contain an unlikely compiler flag. Drop it.
>> >
>> >Signed-off-by: Geliang Tang <geliangtang@163.com>
>>
>> Acked-by: Davidlohr Bueso <dave@stgolabs.net>
>>
>> ... but I believe you do have some left:
>>
>> drivers/scsi/scsi_lib.c: BUG_ON(unlikely(count > ivecs));
>> drivers/scsi/scsi_lib.c: BUG_ON(unlikely(count > queue_max_integrity_segments(rq->q)));
>> kernel/sched/core.c: BUG_ON(unlikely(task_stack_end_corrupted(prev)));
>
>Thanks for your review, the left have been sended out already in two other patches.
So given that the 'unlikely' is based on CONFIG_BUG/HAVE_ARCH_BUG_ON, the
changelog needs to be rewritten. Ie mentioning at least why it should be
ok to drop the redundant predictions: (1) For !CONFIG_BUG cases, the bug call
is a no-op, so we couldn't care less and the change is ok. (2) ppc and
mips, which HAVE_ARCH_BUG_ON, do not rely on branch predictions as it seems
to be pointless[1] and thus callers should not be trying to push an optimization
in the first place.
Also, I think that all the changes should be in the same patch. Logically,
this is a tree wide change, and trivial enough. But I don't really have a
preference.
Thanks,
Davidlohr
[1] http://lkml.iu.edu/hypermail/linux/kernel/1101.3/02289.html
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 3/3] mm/nommu: drop unlikely behind BUG_ON()
@ 2015-10-05 3:37 ` Davidlohr Bueso
0 siblings, 0 replies; 18+ messages in thread
From: Davidlohr Bueso @ 2015-10-05 3:37 UTC (permalink / raw)
To: Geliang Tang
Cc: Andrew Morton, Kirill A. Shutemov, Hugh Dickins,
Peter Zij lstra (Intel),
Andrea Arcangeli, Joonsoo Kim, Arnd Bergmann, Paul Gortmaker,
Leon Romanovsky, Oleg Nesterov, linux-mm, linux-kernel
On Mon, 05 Oct 2015, Geliang Tang wrote:
>On Sun, Oct 04, 2015 at 06:50:55PM -0700, Davidlohr Bueso wrote:
>> On Sun, 04 Oct 2015, Geliang Tang wrote:
>>
>> >BUG_ON() already contain an unlikely compiler flag. Drop it.
>> >
>> >Signed-off-by: Geliang Tang <geliangtang@163.com>
>>
>> Acked-by: Davidlohr Bueso <dave@stgolabs.net>
>>
>> ... but I believe you do have some left:
>>
>> drivers/scsi/scsi_lib.c: BUG_ON(unlikely(count > ivecs));
>> drivers/scsi/scsi_lib.c: BUG_ON(unlikely(count > queue_max_integrity_segments(rq->q)));
>> kernel/sched/core.c: BUG_ON(unlikely(task_stack_end_corrupted(prev)));
>
>Thanks for your review, the left have been sended out already in two other patches.
So given that the 'unlikely' is based on CONFIG_BUG/HAVE_ARCH_BUG_ON, the
changelog needs to be rewritten. Ie mentioning at least why it should be
ok to drop the redundant predictions: (1) For !CONFIG_BUG cases, the bug call
is a no-op, so we couldn't care less and the change is ok. (2) ppc and
mips, which HAVE_ARCH_BUG_ON, do not rely on branch predictions as it seems
to be pointless[1] and thus callers should not be trying to push an optimization
in the first place.
Also, I think that all the changes should be in the same patch. Logically,
this is a tree wide change, and trivial enough. But I don't really have a
preference.
Thanks,
Davidlohr
[1] http://lkml.iu.edu/hypermail/linux/kernel/1101.3/02289.html
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^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 3/3] mm/nommu: drop unlikely behind BUG_ON()
2015-10-05 2:04 ` Davidlohr Bueso
@ 2015-10-05 7:49 ` Leon Romanovsky
-1 siblings, 0 replies; 18+ messages in thread
From: Leon Romanovsky @ 2015-10-05 7:49 UTC (permalink / raw)
To: Geliang Tang, Andrew Morton, Kirill A. Shutemov, Hugh Dickins,
Peter Zijlstra (Intel),
Andrea Arcangeli, Joonsoo Kim, Arnd Bergmann, Paul Gortmaker,
Oleg Nesterov, Linux-MM, linux-kernel
On Sun, Oct 04, 2015 at 07:04:06PM -0700, Davidlohr Bueso wrote:
> On Sun, 04 Oct 2015, Leon Romanovsky wrote:
>
> >On Sun, Oct 4, 2015 at 9:18 AM, Geliang Tang <geliangtang@163.com> wrote:
> >>BUG_ON() already contain an unlikely compiler flag. Drop it.
> >It is not the case if CONFIG_BUG and HAVE_ARCH_BUG_ON are not set.
>
> Yeah, but that's like the 1% of the cases -- and those probably don't even care
> about the branch prediction (I could be wrong). So overall I like getting rid of
> explicit BUG_ON(unlikely(... calls. In fact there's a _reason_ why there are so
> few of them in the kernel.
I agree with you that this change is welcomed and I would like to see it
is accepted.
My main concern that I would expect to see it's coming after the change
of BUG_ON definition to be similar in all places, with "unlikely" in all
definitions, and not instead.
>
> Thanks,
> Davidlohr
^ permalink raw reply [flat|nested] 18+ messages in thread
* Re: [PATCH 3/3] mm/nommu: drop unlikely behind BUG_ON()
@ 2015-10-05 7:49 ` Leon Romanovsky
0 siblings, 0 replies; 18+ messages in thread
From: Leon Romanovsky @ 2015-10-05 7:49 UTC (permalink / raw)
To: Geliang Tang, Andrew Morton, Kirill A. Shutemov, Hugh Dickins,
Peter Zijlstra (Intel),
Andrea Arcangeli, Joonsoo Kim, Arnd Bergmann, Paul Gortmaker,
Oleg Nesterov, Linux-MM, linux-kernel
On Sun, Oct 04, 2015 at 07:04:06PM -0700, Davidlohr Bueso wrote:
> On Sun, 04 Oct 2015, Leon Romanovsky wrote:
>
> >On Sun, Oct 4, 2015 at 9:18 AM, Geliang Tang <geliangtang@163.com> wrote:
> >>BUG_ON() already contain an unlikely compiler flag. Drop it.
> >It is not the case if CONFIG_BUG and HAVE_ARCH_BUG_ON are not set.
>
> Yeah, but that's like the 1% of the cases -- and those probably don't even care
> about the branch prediction (I could be wrong). So overall I like getting rid of
> explicit BUG_ON(unlikely(... calls. In fact there's a _reason_ why there are so
> few of them in the kernel.
I agree with you that this change is welcomed and I would like to see it
is accepted.
My main concern that I would expect to see it's coming after the change
of BUG_ON definition to be similar in all places, with "unlikely" in all
definitions, and not instead.
>
> Thanks,
> Davidlohr
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^ permalink raw reply [flat|nested] 18+ messages in thread
end of thread, other threads:[~2015-10-05 7:53 UTC | newest]
Thread overview: 18+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-10-04 6:18 [PATCH 1/3] scsi: drop unlikely behind BUG_ON() Geliang Tang
2015-10-04 6:18 ` [PATCH 2/3] sched/core: " Geliang Tang
2015-10-04 6:18 ` [PATCH 3/3] mm/nommu: " Geliang Tang
2015-10-04 6:18 ` Geliang Tang
2015-10-04 11:02 ` Leon Romanovsky
2015-10-04 11:02 ` Leon Romanovsky
2015-10-05 2:04 ` Davidlohr Bueso
2015-10-05 2:04 ` Davidlohr Bueso
2015-10-05 7:49 ` Leon Romanovsky
2015-10-05 7:49 ` Leon Romanovsky
2015-10-05 1:50 ` Davidlohr Bueso
2015-10-05 1:50 ` Davidlohr Bueso
2015-10-05 2:30 ` Geliang Tang
2015-10-05 2:30 ` Geliang Tang
2015-10-05 3:37 ` Davidlohr Bueso
2015-10-05 3:37 ` Davidlohr Bueso
2015-10-04 14:33 ` [PATCH 1/3] scsi: " Bart Van Assche
2015-10-04 14:33 ` Bart Van Assche
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