[PATCH RT 1/2][RFC] x86: Do not disable preemption in int3 on 32bit
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2012-01-24 19:15:00
Also in:
lkml
Preemption must be disabled before enabling interrupts in do_trap on x86_64 because the stack in use for int3 and debug is a per CPU stack set by th IST. But in 32bit, the stack still belongs to the current task and there is no problem in scheduling out the task. Keep preemption enabled on X86_32 when enabling interrupts for do_trap(). Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Index: linux-rt.git/arch/x86/kernel/traps.c ===================================================================
--- linux-rt.git.orig/arch/x86/kernel/traps.c
+++ linux-rt.git/arch/x86/kernel/traps.c@@ -89,7 +89,14 @@ static inline void conditional_sti(struc static inline void preempt_conditional_sti(struct pt_regs *regs) { +#ifdef CONFIG_X86_64 + /* + * X86_64 uses a per CPU stack for certain traps like int3. + * We must disable preemption, otherwise we can corrupt the + * stack if the task is scheduled out with this stack. + */ inc_preempt_count(); +#endif if (regs->flags & X86_EFLAGS_IF) local_irq_enable(); }
@@ -104,7 +111,9 @@ static inline void preempt_conditional_c { if (regs->flags & X86_EFLAGS_IF) local_irq_disable(); +#ifdef CONFIG_X86_64 dec_preempt_count(); +#endif } static void __kprobes