linux-kernel - [tip:core/ipi] panic: decrease oops_in_progress only after having done the panic

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Date:	Fri, 13 Mar 2009 10:36:35 GMT
From:	Ingo Molnar <mingo@...e.hu>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	jbeulich@...ell.com, tglx@...utronix.de, mingo@...e.hu
Subject: [tip:core/ipi] panic: decrease oops_in_progress only after having done the panic

Commit-ID:  ffd71da4e3f323b7673b061e6f7e0d0c12dc2b49
Gitweb:     http://git.kernel.org/tip/ffd71da4e3f323b7673b061e6f7e0d0c12dc2b49
Author:     Ingo Molnar <mingo@...e.hu>
AuthorDate: Fri, 13 Mar 2009 10:54:24 +0100
Commit:     Ingo Molnar <mingo@...e.hu>
CommitDate: Fri, 13 Mar 2009 11:06:47 +0100

panic: decrease oops_in_progress only after having done the panic

Impact: eliminate secondary warnings during panic()

We can panic() in a number of difficult, atomic contexts, hence
we use bust_spinlocks(1) in panic() to increase oops_in_progress,
which prevents various debug checks we have in place.

But in practice this protection only covers the first few printk's
done by panic() - it does not cover the later attempt to stop all
other CPUs and kexec(). If a secondary warning triggers in one of
those facilities that can make the panic message scroll off.

So do bust_spinlocks(0) only much later in panic(). (which code
is only reached if panic policy is relaxed that it can return
after a warning message)

Reported-by: Jan Beulich <jbeulich@...ell.com>
LKML-Reference: <49B91A7E.76E4.0078.0@...ell.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>


---
 kernel/panic.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/panic.c b/kernel/panic.c
index 32fe4ef..57fb005 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -77,7 +77,6 @@ NORET_TYPE void panic(const char * fmt, ...)
 #ifdef CONFIG_DEBUG_BUGVERBOSE
 	dump_stack();
 #endif
-	bust_spinlocks(0);
 
 	/*
 	 * If we have crashed and we have a crash kernel loaded let it handle
@@ -136,6 +135,7 @@ NORET_TYPE void panic(const char * fmt, ...)
 		mdelay(1);
 		i++;
 	}
+	bust_spinlocks(0);
 }
 
 EXPORT_SYMBOL(panic);
--
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