Commit af1be5a5 authored by Anton Vorontsov's avatar Anton Vorontsov Committed by Linus Torvalds

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: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarAnton Vorontsov <anton.vorontsov@linaro.org>
Cc: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2214f707
...@@ -29,7 +29,7 @@ void decode_address(char *buf, unsigned long address) ...@@ -29,7 +29,7 @@ void decode_address(char *buf, unsigned long address)
{ {
struct task_struct *p; struct task_struct *p;
struct mm_struct *mm; struct mm_struct *mm;
unsigned long flags, offset; unsigned long offset;
struct rb_node *n; struct rb_node *n;
#ifdef CONFIG_KALLSYMS #ifdef CONFIG_KALLSYMS
...@@ -113,7 +113,7 @@ void decode_address(char *buf, unsigned long address) ...@@ -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 * mappings of all our processes and see if we can't be a whee
* bit more specific * bit more specific
*/ */
write_lock_irqsave(&tasklist_lock, flags); read_lock(&tasklist_lock);
for_each_process(p) { for_each_process(p) {
struct task_struct *t; struct task_struct *t;
...@@ -186,7 +186,7 @@ void decode_address(char *buf, unsigned long address) ...@@ -186,7 +186,7 @@ void decode_address(char *buf, unsigned long address)
sprintf(buf, "/* kernel dynamic memory */"); sprintf(buf, "/* kernel dynamic memory */");
done: done:
write_unlock_irqrestore(&tasklist_lock, flags); read_unlock(&tasklist_lock);
} }
#define EXPAND_LEN ((1 << CONFIG_DEBUG_BFIN_HWTRACE_EXPAND_LEN) * 256 - 1) #define EXPAND_LEN ((1 << CONFIG_DEBUG_BFIN_HWTRACE_EXPAND_LEN) * 256 - 1)
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment