From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756932Ab1LBPqK (ORCPT ); Fri, 2 Dec 2011 10:46:10 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.125]:43513 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754424Ab1LBPqI (ORCPT ); Fri, 2 Dec 2011 10:46:08 -0500 X-Authority-Analysis: v=2.0 cv=Xd0LPfF5 c=1 sm=0 a=ZycB6UtQUfgMyuk2+PxD7w==:17 a=WQKrF2fF-hAA:10 a=5SG0PmZfjMsA:10 a=IkcTkHD0fZMA:10 a=VwQbUJbxAAAA:8 a=20KFwNOVAAAA:8 a=NYJXv619IkKg1yI-x4kA:9 a=KEtRX-mIHa5z8miy_xYA:7 a=QEXdDO2ut3YA:10 a=0kPLrQdw3YYA:10 a=jEp0ucaQiEUA:10 a=Iq1oNnCWIomtHMEa:21 a=3xXwiGiim9Tnpugv:21 a=ZycB6UtQUfgMyuk2+PxD7w==:117 X-Cloudmark-Score: 0 X-Originating-IP: 74.67.80.29 Subject: Re: [PATCH-RT] Fix for sleeping function called from invalid context when running gdb From: Steven Rostedt To: John Kacur Cc: Thomas Gleixner , rt-users , lkml , Andi Kleen In-Reply-To: <1322833159-3846-1-git-send-email-jkacur@redhat.com> References: <1322833159-3846-1-git-send-email-jkacur@redhat.com> Content-Type: text/plain; charset="UTF-8" Date: Fri, 02 Dec 2011 10:46:03 -0500 Message-ID: <1322840763.30977.39.camel@frodo> Mime-Version: 1.0 X-Mailer: Evolution 2.32.3 (2.32.3-1.fc14) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2011-12-02 at 14:39 +0100, John Kacur wrote: > While running gdb on cyclictest on v3.2-rc2-rt3 I got the following error > > [root@starship ~]# [11887.443716] BUG: sleeping function called from invalid con > text at /home/jkacur/linux-rt/kernel/rtmutex.c:645 > [11887.443720] in_atomic(): 1, irqs_disabled(): 0, pid: 4859, name: cyclictest > [11887.443723] no locks held by cyclictest/4859. > [11887.443726] Pid: 4859, comm: cyclictest Not tainted 3.2.0-rc2-rt3-debug-expr+ > #1 > [11887.443728] Call Trace: > [11887.443737] [] __might_sleep+0x185/0x18d > [11887.443743] [] rt_spin_lock_fastlock.clone.0+0x24/0x31 > [11887.443749] [] rt_spin_lock+0x16/0x40 > [11887.443754] [] force_sig_info+0x3d/0xeb > [11887.443758] [] force_sig+0x16/0x18 > [11887.443761] [] do_trap+0xef/0x130 > [11887.443766] [] ? trace_hardirqs_on_caller+0x12a/0x161 > [11887.443771] [] do_int3+0x8d/0x9a > [11887.443774] [] int3+0x27/0x40 > > I found that there is a patch for this in v2.6.33.9-rt31 that I forward-ported > to v3.2-rc2-rt3 > > I believe that Thomas Gleixner is the original author, but I'm not sure. > Thomas - can you provide your signed-off-by if you are the author? Actually, the author was Andi. It's in the 2.6.24-rt patch set too. Here's the change log: >>From ak@suse.de Sat Oct 27 10:32:13 2007 Date: Sat, 27 Oct 2007 12:39:33 +0200 From: Andi Kleen To: linux-rt-users@vger.kernel.org Subject: [PATCH] Don't disable preemption in exception handlers without IST Some of the exception handlers that run on an IST in a normal kernel still disable preemption. This causes might_sleep warning when sending signals for debugging in PREEMPT-RT because sending signals can take a lock. Since the ISTs are disabled now for those don't disable the preemption. This completes the remove IST patch I sent some time ago and fixes another case where using gdb caused warnings. Also it will likely improve latency a little bit. Signed-off-by: Andi Kleen Thomas, I think this patch is worth adding, unless you have a better work around. -- Steve > > Forward-ported from v2.6.33.9-rt31 to v3.2-rc2-rt3 > Signed-off-by: John Kacur > --- > arch/x86/kernel/traps.c | 24 +++++++++++++----------- > 1 files changed, 13 insertions(+), 11 deletions(-) > > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c > index a8e3eb8..3654390 100644 > --- a/arch/x86/kernel/traps.c > +++ b/arch/x86/kernel/traps.c > @@ -87,9 +87,10 @@ static inline void conditional_sti(struct pt_regs *regs) > local_irq_enable(); > } > > -static inline void preempt_conditional_sti(struct pt_regs *regs) > +static inline void preempt_conditional_sti(struct pt_regs *regs, int stack) > { > - inc_preempt_count(); > + if (stack) > + inc_preempt_count(); > if (regs->flags & X86_EFLAGS_IF) > local_irq_enable(); > } > @@ -100,11 +101,12 @@ static inline void conditional_cli(struct pt_regs *regs) > local_irq_disable(); > } > > -static inline void preempt_conditional_cli(struct pt_regs *regs) > +static inline void preempt_conditional_cli(struct pt_regs *regs, int stack) > { > if (regs->flags & X86_EFLAGS_IF) > local_irq_disable(); > - dec_preempt_count(); > + if (stack) > + dec_preempt_count(); > } > > static void __kprobes > @@ -222,9 +224,9 @@ dotraplinkage void do_stack_segment(struct pt_regs *regs, long error_code) > if (notify_die(DIE_TRAP, "stack segment", regs, error_code, > 12, SIGBUS) == NOTIFY_STOP) > return; > - preempt_conditional_sti(regs); > + preempt_conditional_sti(regs, STACKFAULT_STACK); > do_trap(12, SIGBUS, "stack segment", regs, error_code, NULL); > - preempt_conditional_cli(regs); > + preempt_conditional_cli(regs, STACKFAULT_STACK); > } > > dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code) > @@ -316,9 +318,9 @@ dotraplinkage void __kprobes do_int3(struct pt_regs *regs, long error_code) > return; > #endif > > - preempt_conditional_sti(regs); > + preempt_conditional_sti(regs, DEBUG_STACK); > do_trap(3, SIGTRAP, "int3", regs, error_code, NULL); > - preempt_conditional_cli(regs); > + preempt_conditional_cli(regs, DEBUG_STACK); > } > > #ifdef CONFIG_X86_64 > @@ -412,12 +414,12 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code) > return; > > /* It's safe to allow irq's after DR6 has been saved */ > - preempt_conditional_sti(regs); > + preempt_conditional_sti(regs, DEBUG_STACK); > > if (regs->flags & X86_VM_MASK) { > handle_vm86_trap((struct kernel_vm86_regs *) regs, > error_code, 1); > - preempt_conditional_cli(regs); > + preempt_conditional_cli(regs, DEBUG_STACK); > return; > } > > @@ -436,7 +438,7 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code) > si_code = get_si_code(tsk->thread.debugreg6); > if (tsk->thread.debugreg6 & (DR_STEP | DR_TRAP_BITS) || user_icebp) > send_sigtrap(tsk, regs, error_code, si_code); > - preempt_conditional_cli(regs); > + preempt_conditional_cli(regs, DEBUG_STACK); > > return; > }