On 05/09, Sultan Alsawaf wrote: > > On Thu, May 09, 2019 at 05:56:46PM +0200, Oleg Nesterov wrote: > > Impossible ;) I bet lockdep should report the deadlock as soon as find_victims() > > calls find_lock_task_mm() when you already have a locked victim. > > I hope you're not a betting man ;) I am starting to think I am ;) If you have task1 != task2 this code task_lock(task1); task_lock(task2); should trigger print_deadlock_bug(), task1->alloc_lock and task2->alloc_lock are the "same" lock from lockdep pov, held_lock's will have the same hlock_class(). > CONFIG_PROVE_LOCKING=y OK, > And a printk added in vtsk_is_duplicate() to print when a duplicate is detected, in this case find_lock_task_mm() won't be called, and this is what saves us from the actual deadlock. > and my phone's memory cut in half to make simple_lmk do something, this is what > I observed: > taimen:/ # dmesg | grep lockdep > [ 0.000000] \x09RCU lockdep checking is enabled. this reports that CONFIG_PROVE_RCU is enabled ;) > taimen:/ # dmesg | grep simple_lmk > [ 23.211091] simple_lmk: Killing android.carrier with adj 906 to free 37420 kiB > [ 23.211160] simple_lmk: Killing oadcastreceiver with adj 906 to free 36784 kiB yes, looks like simple_lmk has at least 2 locked victims. And I have no idea why you do not see anything else in dmesg. May be debug_locks_off() was already called. But see above, "grep lockdep" won't work. Perhaps you can do "grep -e WARNING -e BUG -e locking". Oleg. _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
