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locking/lockdep: Use for_each_process_thread() for debug_show_all_locks() 

debug_show_all_locks() tries to grab the tasklist_lock for two seconds, but
calling while_each_thread() without tasklist_lock held is not safe.

See the following commit for more information:

  4449a51a7c ("vm_is_stack: use for_each_thread() rather then buggy while_each_thread()")

Change debug_show_all_locks() from "do_each_thread()/while_each_thread()
with possibility of missing tasklist_lock" to "for_each_process_thread()
with RCU", and add a call to touch_all_softlockup_watchdogs() like
show_state_filter() does.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1523011279-8206-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Tetsuo Handa 2018-04-06 19:41:18 +09:00 committed by Ingo Molnar
parent 12e2c41148
commit 0f736a52e4
1 changed files with 8 additions and 35 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

43
kernel/locking/lockdep.c
View File

@ -4451,8 +4451,6 @@ EXPORT_SYMBOL_GPL(debug_check_no_locks_held);
void debug_show_all_locks(void)
{
struct task_struct *g, *p;
int count = 10;
int unlock = 1;
if (unlikely(!debug_locks)) {
pr_warn("INFO: lockdep is turned off.\n");
@ -4460,30 +4458,8 @@ void debug_show_all_locks(void)
}
pr_warn("\nShowing all locks held in the system:\n");
/*
* Here we try to get the tasklist_lock as hard as possible,
* if not successful after 2 seconds we ignore it (but keep
* trying). This is to enable a debug printout even if a
* tasklist_lock-holding task deadlocks or crashes.
*/
retry:
if (!read_trylock(&tasklist_lock)) {
if (count == 10)
pr_warn("hm, tasklist_lock locked, retrying... ");
if (count) {
count--;
pr_cont(" #%d", 10-count);
mdelay(200);
goto retry;
}
pr_cont(" ignoring it.\n");
unlock = 0;
} else {
if (count != 10)
pr_cont(" locked it.\n");
}
do_each_thread(g, p) {
rcu_read_lock();
for_each_process_thread(g, p) {
/*
* It's not reliable to print a task's held locks
* if it's not sleeping (or if it's not the current
@ -4491,19 +4467,16 @@ retry:
*/
if (p->state == TASK_RUNNING && p != current)
continue;
if (p->lockdep_depth)
lockdep_print_held_locks(p);
if (!unlock)
if (read_trylock(&tasklist_lock))
unlock = 1;
if (!p->lockdep_depth)
continue;
lockdep_print_held_locks(p);
touch_nmi_watchdog();
} while_each_thread(g, p);
touch_all_softlockup_watchdogs();
}
rcu_read_unlock();
pr_warn("\n");
pr_warn("=============================================\n\n");
if (unlock)
read_unlock(&tasklist_lock);
}
EXPORT_SYMBOL_GPL(debug_show_all_locks);
#endif