This is a note to let you know that I've just added the patch titled
x86/entry/traps: Don't force in_interrupt() to return true in IST handlers
to the 4.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-entry-traps-don-t-force-in_interrupt-to-return-true-in-ist-handlers.patch
and it can be found in the queue-4.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From aaee8c3c5cce2d9107310dd9f3026b4f901d441c Mon Sep 17 00:00:00 2001
From: Andy Lutomirski <luto@xxxxxxxxxx>
Date: Tue, 24 May 2016 15:54:04 -0700
Subject: x86/entry/traps: Don't force in_interrupt() to return true in IST handlers
From: Andy Lutomirski <luto@xxxxxxxxxx>
commit aaee8c3c5cce2d9107310dd9f3026b4f901d441c upstream.
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@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Fixes: 959274753857 ("x86, traps: Track entry into and exit from IST context")
Link: http://lkml.kernel.org/r/cdc215f94d118d691d73df35275022331156fb45.1464130360.git.luto@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/traps.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -95,6 +95,12 @@ static inline void cond_local_irq_disabl
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)) {
@@ -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();
/* This code is a bit fragile. Test it. */
RCU_LOCKDEP_WARN(!rcu_is_watching(), "ist_enter didn't work");
@@ -123,7 +123,7 @@ 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();
@@ -154,7 +154,7 @@ void ist_begin_non_atomic(struct pt_regs
BUG_ON((unsigned long)(current_top_of_stack() -
current_stack_pointer()) >= THREAD_SIZE);
- preempt_count_sub(HARDIRQ_OFFSET);
+ preempt_enable_no_resched();
}
/**
@@ -164,7 +164,7 @@ void ist_begin_non_atomic(struct pt_regs
*/
void ist_end_non_atomic(void)
{
- preempt_count_add(HARDIRQ_OFFSET);
+ preempt_disable();
}
static nokprobe_inline int
Patches currently in stable-queue which might be from luto@xxxxxxxxxx are
queue-4.6/x86-entry-traps-don-t-force-in_interrupt-to-return-true-in-ist-handlers.patch
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