x86/traps: Get rid of unnecessary preempt_disable/preempt_enable_no_resched (07d495da) · Commits · 戴 / test

Exception handlers which may run on IST stack call ist_enter() at the start of execution and ist_exit() in the end. ist_enter() disables preemption unconditionally and ist_exit() enables it. So the extra preempt_disable/enable() pairs nested inside the ist_enter/exit() regions are pointless and can be removed. Signed-off-by:

Alexander Kuleshov <kuleshovmail@gmail.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Jianyu Zhan <nasa4836@gmail.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@suse.de> Link: http://lkml.kernel.org/r/20161128075057.7724-1-kuleshovmail@gmail.com Signed-off-by:

Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/traps.c

+0 −5

Original line number	Diff line number	Diff line
		@@ -563,11 +563,9 @@ dotraplinkage void notrace do_int3(struct pt_regs *regs, long error_code)
		* as we may switch to the interrupt stack.
		*/
		debug_stack_usage_inc();
		preempt_disable();
		cond_local_irq_enable(regs);
		do_trap(X86_TRAP_BP, SIGTRAP, "int3", regs, error_code, NULL);
		cond_local_irq_disable(regs);
		preempt_enable_no_resched();
		debug_stack_usage_dec();
		exit:
		ist_exit(regs);
		@@ -742,14 +740,12 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code)
		debug_stack_usage_inc();

		/* It's safe to allow irq's after DR6 has been saved */
		preempt_disable();
		cond_local_irq_enable(regs);

		if (v8086_mode(regs)) {
		handle_vm86_trap((struct kernel_vm86_regs *) regs, error_code,
		X86_TRAP_DB);
		cond_local_irq_disable(regs);
		preempt_enable_no_resched();
		debug_stack_usage_dec();
		goto exit;
		}
		@@ -769,7 +765,6 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code)
		if (tsk->thread.debugreg6 & (DR_STEP \| DR_TRAP_BITS) \|\| user_icebp)
		send_sigtrap(tsk, regs, error_code, si_code);
		cond_local_irq_disable(regs);
		preempt_enable_no_resched();
		debug_stack_usage_dec();

		exit:

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