[PATCH 06/10] blackfin: Fix possible deadlock in decode_address()
From: Anton Vorontsov <hidden>
Date: 2012-03-24 10:31:21
Also in:
linux-arm-kernel, linux-mm, linux-sh, linux-um, lkml
Subsystem:
the rest, tracing os noise / latency tracers · Maintainers:
Linus Torvalds, Steven Rostedt
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 <redacted> --- 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 5102cdf..9cc9302 100644
--- a/arch/blackfin/kernel/trace.c
+++ b/arch/blackfin/kernel/trace.c@@ -28,7 +28,7 @@ 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
@@ -112,7 +112,7 @@ 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;
@@ -185,7 +185,7 @@ __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