[PATCH -tip v3 4/7] kprobes/x86: Disable preempt in optprobe

From: Masami Hiramatsu <mhiramat@kernel.org>
To: Ingo Molnar <mingo@kernel.org>, mingo@redhat.com
Cc: x86@kernel.org, Steven Rostedt <rostedt@goodmis.org>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	linux-kernel@vger.kernel.org,
	Peter Zijlstra <peterz@infradead.org>,
	Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	"H . Peter Anvin" <hpa@zytor.com>,
	"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Alexei Starovoitov <ast@fb.com>
Subject: [PATCH -tip v3 4/7] kprobes/x86: Disable preempt in optprobe
Date: Tue, 19 Sep 2017 19:00:59 +0900	[thread overview]
Message-ID: <150581525942.32348.6359217983269060829.stgit@devbox> (raw)
In-Reply-To: <150581509713.32348.1905525476438163954.stgit@devbox>

Disable preempt in optprobe handler as described
in Documentation/kprobes.txt, there is

"Probe handlers are run with preemption disabled."

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 arch/x86/kernel/kprobes/opt.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
index 259b7e828b02..36e4f61c3eec 100644
--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -161,6 +161,7 @@ optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs)
 		return;
 
 	local_irq_save(flags);
+	preempt_disable();
 	if (kprobe_running()) {
 		kprobes_inc_nmissed_count(&op->kp);
 	} else {
@@ -180,6 +181,7 @@ optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs)
 		opt_pre_handler(&op->kp, regs);
 		__this_cpu_write(current_kprobe, NULL);
 	}
+	preempt_enable_no_resched();
 	local_irq_restore(flags);
 }
 NOKPROBE_SYMBOL(optimized_callback);
