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

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Date:   Tue, 19 Sep 2017 19:00:59 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>, mingo@...hat.com
Cc:     x86@...nel.org, Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Alexei Starovoitov <ast@...com>
Subject: [PATCH -tip v3 4/7] kprobes/x86: Disable preempt in optprobe

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@...nel.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);