BUG: warning at kernel/lockdep.c:2427/check_flags()

BUG: warning at kernel/lockdep.c:2427/check_flags()

[Paolo Ornati]

After some hours running 2.6.17-rc6-mm1 + combo-patch I've got this:

[12138.880686] BUG: warning at kernel/lockdep.c:2427/check_flags()
[12138.880692]
[12138.880693] Call Trace:
[12138.880702]  [<ffffffff80240374>] check_flags+0x86/0x201
[12138.880707]  [<ffffffff80240873>] lock_acquire+0x2f/0xa3
[12138.880713]  [<ffffffff8025fcae>] sys_munmap+0x5e/0xa7
[12138.880719]  [<ffffffff8020944e>] system_call+0x7e/0x83
[12138.880723]
[12138.880725] irq event stamp: 18146
[12138.880728] hardirqs last  enabled at (18145): [<ffffffff8049dffc>] _spin_unlock_irq+0x28/0x50
[12138.880734] hardirqs last disabled at (18146): [<ffffffff8049d61e>] trace_hardirqs_off_thunk+0x35/0x67
[12138.880742] softirqs last  enabled at (18112): [<ffffffff8022c1ae>] __do_softirq+0xb2/0xba
[12138.880748] softirqs last disabled at (18105): [<ffffffff8020a2c2>] call_softirq+0x1e/0x28


I don't know if/how it is reproducible.

-- 
	Paolo Ornati
	Linux 2.6.17-rc6-mm1-lockdep on x86_64

Re: BUG: warning at kernel/lockdep.c:2427/check_flags()

[Paolo Ornati]

On Thu, 8 Jun 2006 21:38:09 +0200
Paolo Ornati <ornati@fastwebnet.it> wrote:

> After some hours running 2.6.17-rc6-mm1 + combo-patch I've got this:
> 
> [12138.880686] BUG: warning at kernel/lockdep.c:2427/check_flags()
> [12138.880692]
> [12138.880693] Call Trace:
> [12138.880702]  [<ffffffff80240374>] check_flags+0x86/0x201
> [12138.880707]  [<ffffffff80240873>] lock_acquire+0x2f/0xa3
> [12138.880713]  [<ffffffff8025fcae>] sys_munmap+0x5e/0xa7
> [12138.880719]  [<ffffffff8020944e>] system_call+0x7e/0x83
> [12138.880723]
> [12138.880725] irq event stamp: 18146
> [12138.880728] hardirqs last  enabled at (18145): [<ffffffff8049dffc>] _spin_unlock_irq+0x28/0x50
> [12138.880734] hardirqs last disabled at (18146): [<ffffffff8049d61e>] trace_hardirqs_off_thunk+0x35/0x67
> [12138.880742] softirqs last  enabled at (18112): [<ffffffff8022c1ae>] __do_softirq+0xb2/0xba
> [12138.880748] softirqs last disabled at (18105): [<ffffffff8020a2c2>] call_softirq+0x1e/0x28
> 
> 
> I don't know if/how it is reproducible.

Wow, now I can reproduce it easly :)

Just run under "gdb" a program that segfaults:

void main(void)
{
        *(int*)(0) = 1;
}

and it will trigger.

-- 
	Paolo Ornati
	Linux 2.6.17-rc6-mm1-lockdep on x86_64

Re: BUG: warning at kernel/lockdep.c:2427/check_flags()

[Ingo Molnar]

* Paolo Ornati <ornati@fastwebnet.it> wrote:

> > I don't know if/how it is reproducible.
> 
> Wow, now I can reproduce it easly :)
> 
> Just run under "gdb" a program that segfaults:
> 
> void main(void)
> {
>         *(int*)(0) = 1;
> }
> 
> and it will trigger.

thanks alot, that's very helpful! I'll have a look.

	Ingo

[patch, -rc6-mm1] irqflags tracing: fix x86_64 entry/exit

[Ingo Molnar]

* Paolo Ornati <ornati@fastwebnet.it> wrote:

> Wow, now I can reproduce it easly :)
> 
> Just run under "gdb" a program that segfaults:
> 
> void main(void)
> {
>         *(int*)(0) = 1;
> }
> 
> and it will trigger.

thanks - please try the fix below - it has solved the problem on my 
testbox.

	Ingo

-------------
Subject: irqflags tracing: fix x86_64 entry/exit
From: Ingo Molnar <mingo@elte.hu>

the x86_64 portion of the irqflags code did not properly trace the
"paranoid userspace" type of syscall/ptrace exit variant.

A testcase Paolo Ornati has discovered triggers a lock validator
assert due to this bug.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 arch/x86_64/kernel/entry.S |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

Index: linux/arch/x86_64/kernel/entry.S
===================================================================
--- linux.orig/arch/x86_64/kernel/entry.S
+++ linux/arch/x86_64/kernel/entry.S
@@ -50,9 +50,10 @@
 #define retint_kernel retint_restore_args
 #endif	
 
-.macro TRACE_IRQS_IRETQ
+
+.macro TRACE_IRQS_IRETQ offset=ARGOFFSET
 #ifdef CONFIG_TRACE_IRQFLAGS
-	bt   $9,EFLAGS-ARGOFFSET(%rsp)	/* interrupts off? */
+	bt   $9,EFLAGS-\offset(%rsp)	/* interrupts off? */
 	jnc  1f
 	TRACE_IRQS_ON
 1:
@@ -809,9 +810,9 @@ error_exit:		
 	andl  %edi,%edx
 	jnz  retint_careful
 	/*
-	 * The iret will restore flags:
+	 * The iret might restore flags:
 	 */
-	TRACE_IRQS_ON
+	TRACE_IRQS_IRETQ
 	swapgs 
 	RESTORE_ARGS 0,8,0						
 	jmp iret_label
@@ -999,6 +1000,7 @@ paranoid_exit:
 	testl $3,CS(%rsp)
 	jnz   paranoid_userspace
 paranoid_swapgs:	
+	TRACE_IRQS_IRETQ 0
 	swapgs
 paranoid_restore:	
 	RESTORE_ALL 8

Re: [patch, -rc6-mm1] irqflags tracing: fix x86_64 entry/exit

[Paolo Ornati]

On Fri, 9 Jun 2006 10:59:20 +0200
Ingo Molnar <mingo@elte.hu> wrote:

> > void main(void)
> > {
> >         *(int*)(0) = 1;
> > }
> > 
> > and it will trigger.
> 
> thanks - please try the fix below - it has solved the problem on my 
> testbox.

Works here too.

:)

-- 
	Paolo Ornati
	Linux 2.6.17-rc6-mm1-lockdep on x86_64