From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Gleixner Subject: [PATCH] x86: vm86: fix preemption bug Date: Tue, 13 Jan 2009 23:36:34 +0100 (CET) Message-ID: References: Mime-Version: 1.0 Return-path: In-Reply-To: Sender: kernel-testers-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: TEXT/PLAIN; charset="us-ascii" Content-Transfer-Encoding: 7bit To: "Rafael J. Wysocki" Cc: Linux Kernel Mailing List , Kernel Testers List , Michal Suchanek , Alexander van Heukelum , "H. Peter Anvin" , Ingo Molnar Impact: fix scheduling while atomic bug 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: [] copy_to_user+0x33/0x108 [] save_v86_state+0x65/0x149 [] handle_vm86_trap+0x20/0x8f [] do_debug+0x15b/0x1a4 [] debug_stack_correct+0x27/0x2c [] 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 Cc: stable-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org Signed-off-by: Thomas Gleixner --- arch/x86/kernel/traps.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) Index: linux-2.6/arch/x86/kernel/traps.c =================================================================== --- linux-2.6.orig/arch/x86/kernel/traps.c +++ linux-2.6/arch/x86/kernel/traps.c @@ -99,6 +99,12 @@ 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) @@ -626,8 +632,10 @@ 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