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. Change-Id: I502b9ea50d180aedad7f379ffc0b987d0223d739 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>
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@ -4119,8 +4119,6 @@ EXPORT_SYMBOL_GPL(debug_check_no_locks_held);
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void debug_show_all_locks(void)
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{
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struct task_struct *g, *p;
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int count = 10;
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int unlock = 1;
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if (unlikely(!debug_locks)) {
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printk("INFO: lockdep is turned off.\n");
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@ -4128,30 +4126,8 @@ void debug_show_all_locks(void)
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}
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printk("\nShowing all locks held in the system:\n");
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/*
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* Here we try to get the tasklist_lock as hard as possible,
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* if not successful after 2 seconds we ignore it (but keep
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* trying). This is to enable a debug printout even if a
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* tasklist_lock-holding task deadlocks or crashes.
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*/
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retry:
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if (!read_trylock(&tasklist_lock)) {
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if (count == 10)
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printk("hm, tasklist_lock locked, retrying... ");
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if (count) {
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count--;
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printk(" #%d", 10-count);
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mdelay(200);
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goto retry;
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}
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printk(" ignoring it.\n");
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unlock = 0;
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} else {
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if (count != 10)
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printk(KERN_CONT " locked it.\n");
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}
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do_each_thread(g, p) {
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rcu_read_lock();
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for_each_process_thread(g, p) {
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/*
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* It's not reliable to print a task's held locks
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* if it's not sleeping (or if it's not the current
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@ -4159,19 +4135,16 @@ retry:
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*/
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if (p->state == TASK_RUNNING && p != current)
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continue;
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if (p->lockdep_depth)
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if (!p->lockdep_depth)
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continue;
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lockdep_print_held_locks(p);
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if (!unlock)
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if (read_trylock(&tasklist_lock))
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unlock = 1;
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touch_nmi_watchdog();
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} while_each_thread(g, p);
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touch_all_softlockup_watchdogs();
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}
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rcu_read_unlock();
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printk("\n");
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printk("=============================================\n\n");
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if (unlock)
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read_unlock(&tasklist_lock);
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}
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EXPORT_SYMBOL_GPL(debug_show_all_locks);
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