From: Anton Vorontsov <anton.vorontsov@linaro.org>
To: Andrew Morton <akpm@linux-foundation.org>,
Oleg Nesterov <oleg@redhat.com>
Cc: Russell King <linux@arm.linux.org.uk>,
Mike Frysinger <vapier@gentoo.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Richard Weinberger <richard@nod.at>,
Paul Mundt <lethal@linux-sh.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
John Stultz <john.stultz@linaro.org>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
uclinux-dist-devel@blackfin.uclinux.org,
linuxppc-dev@lists.ozlabs.org, linux-sh@vger.kernel.org,
user-mode-linux-devel@lists.sourceforge.net,
linaro-kernel@lists.linaro.org, patches@linaro.org,
linux-mm@kvack.org
Subject: [PATCH 6/9] blackfin: Fix possible deadlock in decode_address()
Date: Mon, 23 Apr 2012 00:09:15 -0700 [thread overview]
Message-ID: <20120423070915.GF30752@lizard> (raw)
In-Reply-To: <20120423070641.GA27702@lizard>
Oleg Nesterov found an interesting deadlock possibility:
> sysrq_showregs_othercpus() does smp_call_function(showacpu)
> and showacpu() show_stack()->decode_address(). Now suppose that IPI
> interrupts the task holding read_lock(tasklist).
To fix this, blackfin should not grab the write_ variant of the
tasklist lock, read_ one is enough.
Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
---
arch/blackfin/kernel/trace.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/blackfin/kernel/trace.c b/arch/blackfin/kernel/trace.c
index d08f0e3..f7f7a18 100644
--- a/arch/blackfin/kernel/trace.c
+++ b/arch/blackfin/kernel/trace.c
@@ -29,7 +29,7 @@ void decode_address(char *buf, unsigned long address)
{
struct task_struct *p;
struct mm_struct *mm;
- unsigned long flags, offset;
+ unsigned long offset;
struct rb_node *n;
#ifdef CONFIG_KALLSYMS
@@ -113,7 +113,7 @@ void decode_address(char *buf, unsigned long address)
* mappings of all our processes and see if we can't be a whee
* bit more specific
*/
- write_lock_irqsave(&tasklist_lock, flags);
+ read_lock(&tasklist_lock);
for_each_process(p) {
struct task_struct *t;
@@ -186,7 +186,7 @@ __continue:
sprintf(buf, "/* kernel dynamic memory */");
done:
- write_unlock_irqrestore(&tasklist_lock, flags);
+ read_unlock(&tasklist_lock);
}
#define EXPAND_LEN ((1 << CONFIG_DEBUG_BFIN_HWTRACE_EXPAND_LEN) * 256 - 1)
--
1.7.9.2
next prev parent reply other threads:[~2012-04-23 7:10 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-23 7:06 [PATCH v3 0/9] Fixes for common mistakes w/ for_each_process and task->mm Anton Vorontsov
2012-04-23 7:07 ` [PATCH 1/9] cpu: Introduce clear_tasks_mm_cpumask() helper Anton Vorontsov
2012-04-26 23:59 ` Andrew Morton
2012-05-01 10:45 ` Peter Zijlstra
2012-05-05 1:47 ` [PATCH] cpu: Document clear_tasks_mm_cpumask() Anton Vorontsov
2012-05-05 1:47 ` [PATCH 1/9] cpu: Introduce clear_tasks_mm_cpumask() helper Anton Vorontsov
2012-04-23 7:08 ` [PATCH 2/9] arm: Use clear_tasks_mm_cpumask() Anton Vorontsov
2012-04-23 7:08 ` [PATCH 3/9] powerpc: " Anton Vorontsov
2012-04-23 7:08 ` [PATCH 4/9] sh: " Anton Vorontsov
2012-04-23 7:09 ` [PATCH 5/9] blackfin: A couple of task->mm handling fixes Anton Vorontsov
2012-06-01 4:36 ` Mike Frysinger
2012-04-23 7:09 ` Anton Vorontsov [this message]
2012-04-23 7:09 ` [PATCH 7/9] um: Should hold tasklist_lock while traversing processes Anton Vorontsov
2012-04-23 14:57 ` Richard Weinberger
2012-04-23 15:40 ` Anton Vorontsov
2012-04-23 7:09 ` [PATCH 8/9] um: Fix possible race on task->mm Anton Vorontsov
2012-04-23 7:09 ` [PATCH 9/9] um: Properly check all process' threads for a live mm Anton Vorontsov
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