Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933093AbbGVHhh (ORCPT ); Wed, 22 Jul 2015 03:37:37 -0400 Received: from mail4.hitachi.co.jp ([133.145.228.5]:57564 "EHLO mail4.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756130AbbGVHhe (ORCPT ); Wed, 22 Jul 2015 03:37:34 -0400 X-AuditID: 85900ec0-9ebcbb9000001a57-93-55af4813c148 X-Mailbox-Line: From nobody Wed Jul 22 11:14:21 2015 Subject: [PATCH 2/3] kexec: Fix race between panic() and crash_kexec() directly called To: Jonathan Corbet , Peter Zijlstra , Ingo Molnar , "Eric W. Biederman" , "H. Peter Anvin" , Andrew Morton , Thomas Gleixner , Vivek Goyal From: Hidehiro Kawai Cc: Masami Hiramatsu , x86@kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org Date: Wed, 22 Jul 2015 11:14:21 +0900 Message-ID: <20150722021421.5155.99671.stgit@softrs> In-Reply-To: <20150722021421.5155.74460.stgit@softrs> References: <20150722021421.5155.74460.stgit@softrs> User-Agent: StGit/0.16 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3665 Lines: 126 Currently, panic() and crash_kexec() can be called at the same time. For example (x86 case): CPU 0: oops_end() crash_kexec() mutex_trylock() // acquired nmi_shootdown_cpus() // stop other cpus CPU 1: panic() crash_kexec() mutex_trylock() // failed to acquire smp_send_stop() // stop other cpus infinite loop If CPU 1 calls smp_send_stop() before nmi_shootdown_cpus(), kdump fails. In another case: CPU 0: oops_end() crash_kexec() mutex_trylock() // acquired io_check_error() panic() crash_kexec() mutex_trylock() // failed to acquire infinite loop Clearly, this is an undesirable result. To fix this problem, this patch changes crash_kexec() to exclude others by using panic_lock. Signed-off-by: Hidehiro Kawai Cc: Eric Biederman Cc: Vivek Goyal Cc: Andrew Morton --- include/linux/kexec.h | 2 ++ kernel/kexec.c | 12 +++++++++++- kernel/panic.c | 4 ++-- 3 files changed, 15 insertions(+), 3 deletions(-) diff --git a/include/linux/kexec.h b/include/linux/kexec.h index e804306..bd6e477 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -238,6 +238,7 @@ extern int kexec_purgatory_get_set_symbol(struct kimage *image, extern void *kexec_purgatory_get_symbol_addr(struct kimage *image, const char *name); extern void crash_kexec(struct pt_regs *); +extern void __crash_kexec(struct pt_regs *); int kexec_should_crash(struct task_struct *); void crash_save_cpu(struct pt_regs *regs, int cpu); void crash_save_vmcoreinfo(void); @@ -322,6 +323,7 @@ int parse_crashkernel_low(char *cmdline, unsigned long long system_ram, struct pt_regs; struct task_struct; static inline void crash_kexec(struct pt_regs *regs) { } +static inline void __crash_kexec(struct pt_regs *regs) { } static inline int kexec_should_crash(struct task_struct *p) { return 0; } #endif /* CONFIG_KEXEC */ diff --git a/kernel/kexec.c b/kernel/kexec.c index a785c10..fcdd825 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -1470,7 +1470,7 @@ void __weak crash_unmap_reserved_pages(void) #endif /* CONFIG_KEXEC_FILE */ -void crash_kexec(struct pt_regs *regs) +void __crash_kexec(struct pt_regs *regs) { /* Take the kexec_mutex here to prevent sys_kexec_load * running on one cpu from replacing the crash kernel @@ -1493,6 +1493,16 @@ void crash_kexec(struct pt_regs *regs) } } +void crash_kexec(struct pt_regs *regs) +{ + unsigned long flags; + + if (spin_trylock_irqsave(&panic_lock, flags)) { + __crash_kexec(regs); + spin_unlock_irqrestore(&panic_lock, flags); + } +} + size_t crash_get_memory_size(void) { size_t size = 0; diff --git a/kernel/panic.c b/kernel/panic.c index 3c8338b..ce5c8ab 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -135,7 +135,7 @@ void __panic(char *msg) * the "crash_kexec_post_notifiers" option to the kernel. */ if (!crash_kexec_post_notifiers) - crash_kexec(NULL); + __crash_kexec(NULL); /* * Note smp_send_stop is the usual smp shutdown function, which @@ -160,7 +160,7 @@ void __panic(char *msg) * more unstable, it can increase risks of the kdump failure too. */ if (crash_kexec_post_notifiers) - crash_kexec(NULL); + __crash_kexec(NULL); bust_spinlocks(0); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/