Messages in this thread Patch in this message | | | Date | Wed, 18 Feb 2009 13:32:32 -0800 | From | Greg KH <> | Subject | [patch 10/39] x86, vm86: fix preemption bug |
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2.6.28-stable review patch. If anyone has any objections, please let us know.
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From: Thomas Gleixner <tglx@linutronix.de>
commit be716615fe596ee117292dc615e95f707fb67fd1 upstream.
Commit 3d2a71a596bd9c761c8487a2178e95f8a61da083 ("x86, traps: converge do_debug handlers") changed the preemption disable logic of do_debug() so vm86_handle_trap() is called with preemption disabled resulting in:
BUG: sleeping function called from invalid context at include/linux/kernel.h:155 in_atomic(): 1, irqs_disabled(): 0, pid: 3005, name: dosemu.bin Pid: 3005, comm: dosemu.bin Tainted: G W 2.6.29-rc1 #51 Call Trace: [<c050d669>] copy_to_user+0x33/0x108 [<c04181f4>] save_v86_state+0x65/0x149 [<c0418531>] handle_vm86_trap+0x20/0x8f [<c064e345>] do_debug+0x15b/0x1a4 [<c064df1f>] debug_stack_correct+0x27/0x2c [<c040365b>] sysenter_do_call+0x12/0x2f BUG: scheduling while atomic: dosemu.bin/3005/0x10000001
Restore the original calling convention and reenable preemption before calling handle_vm86_trap().
Reported-by: Michal Suchanek <hramrach@centrum.cz> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- arch/x86/kernel/traps.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
--- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -104,6 +104,12 @@ static inline void preempt_conditional_s local_irq_enable(); } +static inline void conditional_cli(struct pt_regs *regs) +{ + if (regs->flags & X86_EFLAGS_IF) + local_irq_disable(); +} + static inline void preempt_conditional_cli(struct pt_regs *regs) { if (regs->flags & X86_EFLAGS_IF) @@ -629,8 +635,10 @@ clear_dr7: #ifdef CONFIG_X86_32 debug_vm86: + /* reenable preemption: handle_vm86_trap() might sleep */ + dec_preempt_count(); handle_vm86_trap((struct kernel_vm86_regs *) regs, error_code, 1); - preempt_conditional_cli(regs); + conditional_cli(regs); return; #endif
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