* [tip:x86/urgent] x86/entry/traps: Don't force in_interrupt() to return true in IST handlers
2016-05-24 22:54 [PATCH v2] x86/traps: Don't force in_interrupt() to return true in IST handlers Andy Lutomirski
@ 2016-06-08 14:28 ` tip-bot for Andy Lutomirski
2016-06-10 12:01 ` [tip:x86/apic] " tip-bot for Andy Lutomirski
2016-06-10 12:50 ` [PATCH v2] x86/traps: " Oleg Nesterov
2 siblings, 0 replies; 4+ messages in thread
From: tip-bot for Andy Lutomirski @ 2016-06-08 14:28 UTC (permalink / raw)
To: linux-tip-commits
Cc: torvalds, oleg, linux-kernel, tglx, dvlasenk, bp, peterz, hpa,
luto, luto, brgerst, mingo
Commit-ID: 30f12b139326febbb3d323aaf02660435ac8aa42
Gitweb: http://git.kernel.org/tip/30f12b139326febbb3d323aaf02660435ac8aa42
Author: Andy Lutomirski <luto@kernel.org>
AuthorDate: Tue, 24 May 2016 15:54:04 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 8 Jun 2016 15:43:06 +0200
x86/entry/traps: Don't force in_interrupt() to return true in IST handlers
Forcing in_interrupt() to return true if we're not in a bona fide
interrupt confuses the softirq code. This fixes warnings like:
NOHZ: local_softirq_pending 282
... which can happen when running things like selftests/x86.
This will change perf's static percpu buffer usage in IST context.
I think this is okay, and it's changing the behavior to match
historical (pre-4.0) behavior.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Fixes: 959274753857 ("x86, traps: Track entry into and exit from IST context")
Link: http://lkml.kernel.org/r/cdc215f94d118d691d73df35275022331156fb45.1464130360.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/traps.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index d159048..00f03d8 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -96,6 +96,12 @@ static inline void cond_local_irq_disable(struct pt_regs *regs)
local_irq_disable();
}
+/*
+ * In IST context, we explicitly disable preemption. This serves two
+ * purposes: it makes it much less likely that we would accidentally
+ * schedule in IST context and it will force a warning if we somehow
+ * manage to schedule by accident.
+ */
void ist_enter(struct pt_regs *regs)
{
if (user_mode(regs)) {
@@ -110,13 +116,7 @@ void ist_enter(struct pt_regs *regs)
rcu_nmi_enter();
}
- /*
- * We are atomic because we're on the IST stack; or we're on
- * x86_32, in which case we still shouldn't schedule; or we're
- * on x86_64 and entered from user mode, in which case we're
- * still atomic unless ist_begin_non_atomic is called.
- */
- preempt_count_add(HARDIRQ_OFFSET);
+ preempt_disable();
/* This code is a bit fragile. Test it. */
RCU_LOCKDEP_WARN(!rcu_is_watching(), "ist_enter didn't work");
@@ -124,7 +124,7 @@ void ist_enter(struct pt_regs *regs)
void ist_exit(struct pt_regs *regs)
{
- preempt_count_sub(HARDIRQ_OFFSET);
+ preempt_enable_no_resched();
if (!user_mode(regs))
rcu_nmi_exit();
@@ -155,7 +155,7 @@ void ist_begin_non_atomic(struct pt_regs *regs)
BUG_ON((unsigned long)(current_top_of_stack() -
current_stack_pointer()) >= THREAD_SIZE);
- preempt_count_sub(HARDIRQ_OFFSET);
+ preempt_enable_no_resched();
}
/**
@@ -165,7 +165,7 @@ void ist_begin_non_atomic(struct pt_regs *regs)
*/
void ist_end_non_atomic(void)
{
- preempt_count_add(HARDIRQ_OFFSET);
+ preempt_disable();
}
static nokprobe_inline int
^ permalink raw reply related [flat|nested] 4+ messages in thread* [tip:x86/apic] x86/entry/traps: Don't force in_interrupt() to return true in IST handlers
2016-05-24 22:54 [PATCH v2] x86/traps: Don't force in_interrupt() to return true in IST handlers Andy Lutomirski
2016-06-08 14:28 ` [tip:x86/urgent] x86/entry/traps: " tip-bot for Andy Lutomirski
@ 2016-06-10 12:01 ` tip-bot for Andy Lutomirski
2016-06-10 12:50 ` [PATCH v2] x86/traps: " Oleg Nesterov
2 siblings, 0 replies; 4+ messages in thread
From: tip-bot for Andy Lutomirski @ 2016-06-10 12:01 UTC (permalink / raw)
To: linux-tip-commits
Cc: peterz, luto, oleg, brgerst, mingo, linux-kernel, tglx, luto,
torvalds, hpa, dvlasenk, bp
Commit-ID: aaee8c3c5cce2d9107310dd9f3026b4f901d441c
Gitweb: http://git.kernel.org/tip/aaee8c3c5cce2d9107310dd9f3026b4f901d441c
Author: Andy Lutomirski <luto@kernel.org>
AuthorDate: Tue, 24 May 2016 15:54:04 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 10 Jun 2016 13:54:47 +0200
x86/entry/traps: Don't force in_interrupt() to return true in IST handlers
Forcing in_interrupt() to return true if we're not in a bona fide
interrupt confuses the softirq code. This fixes warnings like:
NOHZ: local_softirq_pending 282
... which can happen when running things like selftests/x86.
This will change perf's static percpu buffer usage in IST context.
I think this is okay, and it's changing the behavior to match
historical (pre-4.0) behavior.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Fixes: 959274753857 ("x86, traps: Track entry into and exit from IST context")
Link: http://lkml.kernel.org/r/cdc215f94d118d691d73df35275022331156fb45.1464130360.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/traps.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index d159048..00f03d8 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -96,6 +96,12 @@ static inline void cond_local_irq_disable(struct pt_regs *regs)
local_irq_disable();
}
+/*
+ * In IST context, we explicitly disable preemption. This serves two
+ * purposes: it makes it much less likely that we would accidentally
+ * schedule in IST context and it will force a warning if we somehow
+ * manage to schedule by accident.
+ */
void ist_enter(struct pt_regs *regs)
{
if (user_mode(regs)) {
@@ -110,13 +116,7 @@ void ist_enter(struct pt_regs *regs)
rcu_nmi_enter();
}
- /*
- * We are atomic because we're on the IST stack; or we're on
- * x86_32, in which case we still shouldn't schedule; or we're
- * on x86_64 and entered from user mode, in which case we're
- * still atomic unless ist_begin_non_atomic is called.
- */
- preempt_count_add(HARDIRQ_OFFSET);
+ preempt_disable();
/* This code is a bit fragile. Test it. */
RCU_LOCKDEP_WARN(!rcu_is_watching(), "ist_enter didn't work");
@@ -124,7 +124,7 @@ void ist_enter(struct pt_regs *regs)
void ist_exit(struct pt_regs *regs)
{
- preempt_count_sub(HARDIRQ_OFFSET);
+ preempt_enable_no_resched();
if (!user_mode(regs))
rcu_nmi_exit();
@@ -155,7 +155,7 @@ void ist_begin_non_atomic(struct pt_regs *regs)
BUG_ON((unsigned long)(current_top_of_stack() -
current_stack_pointer()) >= THREAD_SIZE);
- preempt_count_sub(HARDIRQ_OFFSET);
+ preempt_enable_no_resched();
}
/**
@@ -165,7 +165,7 @@ void ist_begin_non_atomic(struct pt_regs *regs)
*/
void ist_end_non_atomic(void)
{
- preempt_count_add(HARDIRQ_OFFSET);
+ preempt_disable();
}
static nokprobe_inline int
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH v2] x86/traps: Don't force in_interrupt() to return true in IST handlers
2016-05-24 22:54 [PATCH v2] x86/traps: Don't force in_interrupt() to return true in IST handlers Andy Lutomirski
2016-06-08 14:28 ` [tip:x86/urgent] x86/entry/traps: " tip-bot for Andy Lutomirski
2016-06-10 12:01 ` [tip:x86/apic] " tip-bot for Andy Lutomirski
@ 2016-06-10 12:50 ` Oleg Nesterov
2 siblings, 0 replies; 4+ messages in thread
From: Oleg Nesterov @ 2016-06-10 12:50 UTC (permalink / raw)
To: Andy Lutomirski
Cc: x86, linux-kernel, Borislav Petkov, Andi Kleen, stable,
Alexander Kuleshov
On 05/24, Andy Lutomirski wrote:
>
> void ist_enter(struct pt_regs *regs)
> {
> if (user_mode(regs)) {
> @@ -109,13 +115,7 @@ void ist_enter(struct pt_regs *regs)
> rcu_nmi_enter();
> }
>
> - /*
> - * We are atomic because we're on the IST stack; or we're on
> - * x86_32, in which case we still shouldn't schedule; or we're
> - * on x86_64 and entered from user mode, in which case we're
> - * still atomic unless ist_begin_non_atomic is called.
> - */
> - preempt_count_add(HARDIRQ_OFFSET);
> + preempt_disable();
off-topic question,
perhaps it makes sense to remove another preempt_disable/preempt_enable_no_resched
in do_int3() and do_debug() ?
They were added by d99e1bd175f4291ddb6e62b22bb5bdbe3976389a ("x86/entry/traps: Refactor
preemption and interrupt flag handling") and afaics for no reason.
Oleg.
^ permalink raw reply [flat|nested] 4+ messages in thread