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authorAndy Lutomirski <luto@kernel.org>2016-05-24 15:54:04 -0700
committerIngo Molnar <mingo@kernel.org>2016-06-10 13:54:47 +0200
commitaaee8c3c5cce2d9107310dd9f3026b4f901d441c (patch)
tree8b10873439a9d961d0f3a75076ade112c5bbe4c5
parent96685a55a82c383cbba7ef1d4a636acf708cf17f (diff)
downloadlinux-aaee8c3c5cce2d9107310dd9f3026b4f901d441c.tar.gz
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>
-rw-r--r--arch/x86/kernel/traps.c20
1 files changed, 10 insertions, 10 deletions
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index d1590486204a..00f03d82e69a 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