The patch titled
Subject: blackfin: fix possible deadlock in decode_address()
has been added to the -mm tree. Its filename is
blackfin-fix-possible-deadlock-in-decode_address.patch
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From: Anton Vorontsov <anton.vorontsov@xxxxxxxxxx>
Subject: 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@xxxxxxxxxx>
Signed-off-by: Anton Vorontsov <anton.vorontsov@xxxxxxxxxx>
Cc: Mike Frysinger <vapier@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/blackfin/kernel/trace.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff -puN arch/blackfin/kernel/trace.c~blackfin-fix-possible-deadlock-in-decode_address arch/blackfin/kernel/trace.c
--- a/arch/blackfin/kernel/trace.c~blackfin-fix-possible-deadlock-in-decode_address
+++ a/arch/blackfin/kernel/trace.c
@@ -29,7 +29,7 @@ void decode_address(char *buf, unsigned
{
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
* 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)
_
Subject: Subject: blackfin: fix possible deadlock in decode_address()
Patches currently in -mm which might be from anton.vorontsov@xxxxxxxxxx are
cpu-introduce-clear_tasks_mm_cpumask-helper.patch
arm-use-clear_tasks_mm_cpumask.patch
powerpc-use-clear_tasks_mm_cpumask.patch
sh-use-clear_tasks_mm_cpumask.patch
blackfin-a-couple-of-task-mm-handling-fixes.patch
blackfin-fix-possible-deadlock-in-decode_address.patch
um-should-hold-tasklist_lock-while-traversing-processes.patch
um-fix-possible-race-on-task-mm.patch
um-properly-check-all-process-threads-for-a-live-mm.patch
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