x86/entry/traps: Don't force in_interrupt() to return true in IST handlers (aaee8c3c) · Commits · 戴 / test

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: ("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

+10 −10

Original line number	Diff line number	Diff line
		@@ -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

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