linux-kernel - [PATCH] Fix kexec abort due to IPI from panic().

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Message-ID: <5C4C569E8A4B9B42A84A977CF070A35B2C0979C90E@USINDEVS01.corp.hds.com>
Date:	Thu, 16 Sep 2010 16:16:14 -0400
From:	Seiji Aguchi <seiji.aguchi@....com>
To:	"ebiederm@...ssion.com" <ebiederm@...ssion.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"xiyou.wangcong@...il.com" <xiyou.wangcong@...il.com>,
	"paulmck@...ux.vnet.ibm.com" <paulmck@...ux.vnet.ibm.com>,
	"simon.kagstrom@...insight.net" <simon.kagstrom@...insight.net>,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	Satoru Moriya <satoru.moriya@....com>,
	"dle-develop@...ts.sourceforge.net" 
	<dle-develop@...ts.sourceforge.net>
Subject: [PATCH] Fix kexec abort due to IPI from panic().

Hi,

I'm Seiji Aguchi.
I work for Hitachi Data Systems.
It's a first time to send a patch to lkml.
Nice to meet you.

I found an issue in kexec.
Please give me your comments and suggestions.

Kexec abort when two cpus panic at the same time.
An example scenario:
1. Two cpus panic at the same time .
2. One cpu ,cpu0, get kexec_mutex in crash_kexec().
3. The other cpu ,cpu1, can't get kexec_mutex and return from crash_kexec().
4. Cpu0 runs kmsg_dump(KMSG_DUMP_KEXEC).
5. Cpu1 can't get dump_list_lock and return from kmsg_dump(KMSG_DUMP_PANIC).
6. Cpu1 runs smp_send_stop() in panic() and sends IPI to other cpus.
7. Cpu0 may receive IPI from cpu1 while running kmsg_dump(KMSG_DUMP_KEXEC),
   crash_setup_regs(), or crash_save_vmcore().

We can solve this issue by disabling external interrupt while getting kexec_mutex 
in crash_kexec().

 Signed-off-by: Seiji Aguchi <seiji.aguchi@....com>

---
 kernel/kexec.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/kernel/kexec.c b/kernel/kexec.c
index c0613f7..9e9f159 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -1075,6 +1075,10 @@ void crash_kexec(struct pt_regs *regs)
 	 * sufficient.  But since I reuse the memory...
 	 */
 	if (mutex_trylock(&kexec_mutex)) {
+		unsigned long flags;
+
+		local_irq_save(flags);
+
 		if (kexec_crash_image) {
 			struct pt_regs fixed_regs;

@@ -1085,6 +1089,9 @@ void crash_kexec(struct pt_regs *regs)
 			machine_crash_shutdown(&fixed_regs);
 			machine_kexec(kexec_crash_image);
 		}
+
+		local_irq_restore(flags);
+
 		mutex_unlock(&kexec_mutex);
 	}
 }
-- 
1.7.2.2

Regards,

Seiji
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