* [PATCH v2 0/9] entry: preempt_schedule_irq() callers scrub
@ 2019-09-23 14:36 Valentin Schneider
2019-09-23 14:36 ` [PATCH v2 1/9] sched/core: Fix preempt_schedule() interrupt return comment Valentin Schneider
2019-09-23 14:36 ` [PATCH v2 6/9] RISC-V: entry: Remove unneeded need_resched() loop Valentin Schneider
0 siblings, 2 replies; 5+ messages in thread
From: Valentin Schneider @ 2019-09-23 14:36 UTC (permalink / raw)
To: linux-kernel
Cc: uclinux-h8-devel, linux-xtensa, linux-c6x-dev, linux-sh,
Peter Zijlstra, Ingo Molnar, Thomas Gleixner, linux-riscv
I've left this to ~rot~ age out in the sun for a while, apologies for that.
One early new-year resolution for me is to maintain a shorter resend
timeout on this.
This is the continuation of [1] where I'm hunting down
preempt_schedule_irq() callers because of [2]. I've looked at users of
preempt_schedule_irq(), and made sure they didn't have one of those useless
loops. The list of offenders is:
$ grep -r -I "preempt_schedule_irq" arch/ | cut -d/ -f2 | sort | uniq
arc
arm
arm64
c6x
csky
h8300
ia64
m68k
microblaze
mips
nds32
nios2
parisc
powerpc
riscv
s390
sh
sparc
x86
xtensa
Regarding that loop, archs seem to fall in 3 categories:
A) Those that don't have the loop
B) Those that have a small need_resched() loop around the
preempt_schedule_irq() callsite
C) Those that branch to some more generic code further up the entry code
and eventually branch back to preempt_schedule_irq()
arc, m68k, nios2 fall in A)
sparc, ia64, s390 fall in C)
all the others fall in B)
I've written patches for B). As of 5.3 mainline contains those for:
- arm64
- mips
- x86
- powerpc
- nds32
I've also got acks/reviews but haven't seen in any tree yet for:
- c6x
- csky
- riscv
- xtensa
The remaining ones for which I haven't had any reply at all are
- h8300
- microblaze
- sh
- sh64
Build-tested:
- h8300
- c6x
- microblaze
- riscv
No major change since v1 other than rebasing on top of 5.4 and collecting
Reviewed-By / Acked-By.
Thanks,
Valentin
[1]: https://lore.kernel.org/lkml/20190131182339.9835-1-valentin.schneider@arm.com/
[2]: https://lore.kernel.org/lkml/cc989920-a13b-d53b-db83-1584a7f53edc@arm.com/
Valentin Schneider (9):
sched/core: Fix preempt_schedule() interrupt return comment
c6x: entry: Remove unneeded need_resched() loop
csky: entry: Remove unneeded need_resched() loop
h8300: entry: Remove unneeded need_resched() loop
microblaze: entry: Remove unneeded need_resched() loop
RISC-V: entry: Remove unneeded need_resched() loop
sh: entry: Remove unneeded need_resched() loop
sh64: entry: Remove unneeded need_resched() loop
xtensa: entry: Remove unneeded need_resched() loop
arch/c6x/kernel/entry.S | 3 +--
arch/csky/kernel/entry.S | 4 ----
arch/h8300/kernel/entry.S | 3 +--
arch/microblaze/kernel/entry.S | 5 -----
arch/riscv/kernel/entry.S | 3 +--
arch/sh/kernel/cpu/sh5/entry.S | 5 +----
arch/sh/kernel/entry-common.S | 4 +---
arch/xtensa/kernel/entry.S | 2 +-
kernel/sched/core.c | 7 +++----
9 files changed, 9 insertions(+), 27 deletions(-)
--
2.22.0
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^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH v2 1/9] sched/core: Fix preempt_schedule() interrupt return comment
2019-09-23 14:36 [PATCH v2 0/9] entry: preempt_schedule_irq() callers scrub Valentin Schneider
@ 2019-09-23 14:36 ` Valentin Schneider
2019-09-27 8:10 ` [tip: sched/urgent] " tip-bot2 for Valentin Schneider
2019-09-23 14:36 ` [PATCH v2 6/9] RISC-V: entry: Remove unneeded need_resched() loop Valentin Schneider
1 sibling, 1 reply; 5+ messages in thread
From: Valentin Schneider @ 2019-09-23 14:36 UTC (permalink / raw)
To: linux-kernel
Cc: uclinux-h8-devel, linux-sh, Peter Zijlstra, linux-m68k,
Ingo Molnar, Thomas Gleixner, linux-riscv
preempt_schedule_irq() is the one that should be called on return from
interrupt, clean up the comment to avoid any ambiguity.
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
---
kernel/sched/core.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f9a1346a5fa9..3f40ea9f1372 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4223,9 +4223,8 @@ static void __sched notrace preempt_schedule_common(void)
#ifdef CONFIG_PREEMPTION
/*
- * this is the entry point to schedule() from in-kernel preemption
- * off of preempt_enable. Kernel preemptions off return from interrupt
- * occur there and call schedule directly.
+ * This is the entry point to schedule() from in-kernel preemption
+ * off of preempt_enable.
*/
asmlinkage __visible void __sched notrace preempt_schedule(void)
{
@@ -4296,7 +4295,7 @@ EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
#endif /* CONFIG_PREEMPTION */
/*
- * this is the entry point to schedule() from kernel preemption
+ * This is the entry point to schedule() from kernel preemption
* off of irq context.
* Note, that this is called and return with irqs disabled. This will
* protect us against recursive calling from irq.
--
2.22.0
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^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH v2 6/9] RISC-V: entry: Remove unneeded need_resched() loop
2019-09-23 14:36 [PATCH v2 0/9] entry: preempt_schedule_irq() callers scrub Valentin Schneider
2019-09-23 14:36 ` [PATCH v2 1/9] sched/core: Fix preempt_schedule() interrupt return comment Valentin Schneider
@ 2019-09-23 14:36 ` Valentin Schneider
2019-10-09 0:51 ` Paul Walmsley
1 sibling, 1 reply; 5+ messages in thread
From: Valentin Schneider @ 2019-09-23 14:36 UTC (permalink / raw)
To: linux-kernel; +Cc: linux-riscv, Palmer Dabbelt, Albert Ou
Since the enabling and disabling of IRQs within preempt_schedule_irq()
is contained in a need_resched() loop, we don't need the outer arch
code loop.
Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: linux-riscv@lists.infradead.org
---
arch/riscv/kernel/entry.S | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index 74ccfd464071..d0523167d261 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -250,12 +250,11 @@ restore_all:
resume_kernel:
REG_L s0, TASK_TI_PREEMPT_COUNT(tp)
bnez s0, restore_all
-need_resched:
REG_L s0, TASK_TI_FLAGS(tp)
andi s0, s0, _TIF_NEED_RESCHED
beqz s0, restore_all
call preempt_schedule_irq
- j need_resched
+ j restore_all
#endif
work_pending:
--
2.22.0
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^ permalink raw reply related [flat|nested] 5+ messages in thread
* [tip: sched/urgent] sched/core: Fix preempt_schedule() interrupt return comment
2019-09-23 14:36 ` [PATCH v2 1/9] sched/core: Fix preempt_schedule() interrupt return comment Valentin Schneider
@ 2019-09-27 8:10 ` tip-bot2 for Valentin Schneider
0 siblings, 0 replies; 5+ messages in thread
From: tip-bot2 for Valentin Schneider @ 2019-09-27 8:10 UTC (permalink / raw)
To: linux-tip-commits
Cc: uclinux-h8-devel, Peter Zijlstra (Intel),
linux-kernel, linux-riscv, Ingo Molnar, linux-m68k,
Borislav Petkov, Thomas Gleixner, Linus Torvalds,
Valentin Schneider
The following commit has been merged into the sched/urgent branch of tip:
Commit-ID: a49b4f4012ef233143c5f7ce44f97851e54d5ef9
Gitweb: https://git.kernel.org/tip/a49b4f4012ef233143c5f7ce44f97851e54d5ef9
Author: Valentin Schneider <valentin.schneider@arm.com>
AuthorDate: Mon, 23 Sep 2019 15:36:12 +01:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Wed, 25 Sep 2019 17:42:32 +02:00
sched/core: Fix preempt_schedule() interrupt return comment
preempt_schedule_irq() is the one that should be called on return from
interrupt, clean up the comment to avoid any ambiguity.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-m68k@lists.linux-m68k.org
Cc: linux-riscv@lists.infradead.org
Cc: uclinux-h8-devel@lists.sourceforge.jp
Link: https://lkml.kernel.org/r/20190923143620.29334-2-valentin.schneider@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/sched/core.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 83ea23e..00ef44c 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4218,9 +4218,8 @@ static void __sched notrace preempt_schedule_common(void)
#ifdef CONFIG_PREEMPTION
/*
- * this is the entry point to schedule() from in-kernel preemption
- * off of preempt_enable. Kernel preemptions off return from interrupt
- * occur there and call schedule directly.
+ * This is the entry point to schedule() from in-kernel preemption
+ * off of preempt_enable.
*/
asmlinkage __visible void __sched notrace preempt_schedule(void)
{
@@ -4291,7 +4290,7 @@ EXPORT_SYMBOL_GPL(preempt_schedule_notrace);
#endif /* CONFIG_PREEMPTION */
/*
- * this is the entry point to schedule() from kernel preemption
+ * This is the entry point to schedule() from kernel preemption
* off of irq context.
* Note, that this is called and return with irqs disabled. This will
* protect us against recursive calling from irq.
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^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH v2 6/9] RISC-V: entry: Remove unneeded need_resched() loop
2019-09-23 14:36 ` [PATCH v2 6/9] RISC-V: entry: Remove unneeded need_resched() loop Valentin Schneider
@ 2019-10-09 0:51 ` Paul Walmsley
0 siblings, 0 replies; 5+ messages in thread
From: Paul Walmsley @ 2019-10-09 0:51 UTC (permalink / raw)
To: Valentin Schneider; +Cc: linux-riscv, Palmer Dabbelt, linux-kernel, Albert Ou
On Mon, 23 Sep 2019, Valentin Schneider wrote:
> Since the enabling and disabling of IRQs within preempt_schedule_irq()
> is contained in a need_resched() loop, we don't need the outer arch
> code loop.
>
> Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
> Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
> Cc: Albert Ou <aou@eecs.berkeley.edu>
> Cc: linux-riscv@lists.infradead.org
Thanks, queued for v5.4-rc.
- Paul
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^ permalink raw reply [flat|nested] 5+ messages in thread
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2019-09-23 14:36 [PATCH v2 0/9] entry: preempt_schedule_irq() callers scrub Valentin Schneider
2019-09-23 14:36 ` [PATCH v2 1/9] sched/core: Fix preempt_schedule() interrupt return comment Valentin Schneider
2019-09-27 8:10 ` [tip: sched/urgent] " tip-bot2 for Valentin Schneider
2019-09-23 14:36 ` [PATCH v2 6/9] RISC-V: entry: Remove unneeded need_resched() loop Valentin Schneider
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