diff options
| author | Anton Vorontsov <anton.vorontsov@linaro.org> | 2012-06-01 03:26:24 +0400 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-06-01 04:49:30 +0400 |
| commit | af1be5a578a1ccc9961c55290f8c509a00a69036 (patch) | |
| tree | f8659ba36228582a114c7809bdf580640eb626cf | |
| parent | 2214f707de257c35773d5cd68cec9e31b91e01ca (diff) | |
| download | linux-af1be5a578a1ccc9961c55290f8c509a00a69036.tar.xz | |
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@redhat.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Cc: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | arch/blackfin/kernel/trace.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/arch/blackfin/kernel/trace.c b/arch/blackfin/kernel/trace.c index d08f0e3e2dcc..f7f7a18abca9 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) |