On Fri 2025-01-31 21:22:13, zhang warden wrote: > > > > On Jan 22, 2025, at 20:50, Petr Mladek <pmladek@xxxxxxxx> wrote: > > > > With this patch, any operation which takes the tasklist_lock might > > break klp_try_complete_transition(). I am afraid that this might > > block the transition for a long time on huge systems with some > > specific loads. > > > > And the problem is caused by a printk() added just for debugging. > > I wonder if you even use a slow serial port. > > > > You might try to use printk_deferred() instead. Also you might need > > to disable interrupts around the read_lock()/read_unlock() to > > make sure that the console handling will be deferred after > > the tasklist_lock gets released. > > > > Anyway, I am against this patch. > > > > Best Regards, > > Petr > > Hi, Petr. > > I am unfamiliar with the function `rwlock_is_contended`, but it seems this function will not block and just only check the status of the rw_lock. > > If I understand it right, the problem would raise from the `break` which will stop the process of `for_each_process_thread`, right? You got it right. I am afraid that it might create a livelock situation for the livepatch transition. I mean that the check might almost always break on systems with thousands of processes and frequently created/exited processes. It always has to start from the beginning. Best Regards, Petr
