Re: [PATCH 2/2] ptrace: fix set_task_blockstep()->update_debugctlmsr()logic
From: Sebastian Andrzej Siewior
Date: Fri Aug 03 2012 - 12:43:22 EST
On 08/03/2012 06:29 PM, Oleg Nesterov wrote:
diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c
index afa60db..636402e 100644
--- a/arch/x86/kernel/step.c
+++ b/arch/x86/kernel/step.c
@@ -166,12 +166,18 @@ static void set_task_blockstep(struct task_struct *task, bool on)
else
clear_tsk_thread_flag(task, TIF_BLOCKSTEP);
+ if (task != current)
+ return;
+
+ /* ensure irq/preemption can't change debugctl in between */
+ local_irq_disable();
debugctl = get_debugctlmsr();
if (on)
debugctl |= DEBUGCTLMSR_BTF;
else
debugctl&= ~DEBUGCTLMSR_BTF;
update_debugctlmsr(debugctl);
+ local_irq_enable();
wouldn't preempt_disable() be enough?
}
/*
Sebastian
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