Commit-ID: 0f736a52e4be86476eec1d5adbcbd9c2809ac4b4
Gitweb: https://git.kernel.org/tip/0f736a52e4be86476eec1d5adbcbd9c2809ac4b4
Author: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp>
AuthorDate: Fri, 6 Apr 2018 19:41:18 +0900
Committer: Ingo Molnar <mi...@kernel.org>
CommitDate: Mon, 14 May 2018 09:15:02 +0200
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:
4449a51a7c281602 ("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-ker...@i-love.sakura.ne.jp>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Link:
http://lkml.kernel.org/r/1523011279-8206-1-git-send-email-penguin-ker...@i-love.sakura.ne.jp
Signed-off-by: Ingo Molnar <mi...@kernel.org>
---
kernel/locking/lockdep.c | 43 ++++++++-----------------------------------
1 file changed, 8 insertions(+), 35 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 023386338269..94f4d21ff66d 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -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
