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author | Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> | 2018-04-06 19:41:18 +0900 |
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committer | Ingo Molnar <mingo@kernel.org> | 2018-05-14 09:15:02 +0200 |
commit | 0f736a52e4be86476eec1d5adbcbd9c2809ac4b4 (patch) | |
tree | d1a995699c621493e9e7e45c0bf64d404b3c26aa /kernel/locking | |
parent | 12e2c41148a9e68bc3b261954961db9d28decf47 (diff) | |
download | op-kernel-dev-0f736a52e4be86476eec1d5adbcbd9c2809ac4b4.zip op-kernel-dev-0f736a52e4be86476eec1d5adbcbd9c2809ac4b4.tar.gz |
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-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>
Diffstat (limited to 'kernel/locking')
-rw-r--r-- | kernel/locking/lockdep.c | 43 |
1 files changed, 8 insertions, 35 deletions
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 0233863..94f4d21 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 |