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Date: Mon, 23 Apr 2012 00:09:15 -0700 From: Anton Vorontsov <anton.vorontsov@...aro.org> To: Andrew Morton <akpm@...ux-foundation.org>, Oleg Nesterov <oleg@...hat.com> Cc: Russell King <linux@....linux.org.uk>, Mike Frysinger <vapier@...too.org>, Benjamin Herrenschmidt <benh@...nel.crashing.org>, Richard Weinberger <richard@....at>, Paul Mundt <lethal@...ux-sh.org>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>, John Stultz <john.stultz@...aro.org>, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, uclinux-dist-devel@...ckfin.uclinux.org, linuxppc-dev@...ts.ozlabs.org, linux-sh@...r.kernel.org, user-mode-linux-devel@...ts.sourceforge.net, linaro-kernel@...ts.linaro.org, patches@...aro.org, linux-mm@...ck.org Subject: [PATCH 6/9] blackfin: Fix possible deadlock in decode_address() 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@...hat.com> Signed-off-by: Anton Vorontsov <anton.vorontsov@...aro.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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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