Hi Anton, On Tue, Aug 15, 2017 at 04:46:25PM +0300, Anton Volkov wrote: > Hello. > > While searching for races in the Linux kernel I've come across > "drivers/input/touchscreen/ucb1400_ts.ko" module. Here is a question > that I came up with while analyzing results. Lines are given using > the info from Linux v4.12. > > Consider the following case: > > Thread 1: Thread 2: > ucb1400_suspend > ->ucb1400_ts_start > ucb->stopped = false > enable_irq() > > ucb1400_resume > ->ucb1400_ts_stop ucb1400_irq > ucb->stopped = true while(!ucb->stopped && ...) > (ucb1400_ts.c: line 230) (ucb1400_ts.c: line 202) > disable_irq() > > The value of ucb->stopped may be changed in the midst of 'while' > loop iterations or prevent all of them from happening. Is this > feasible from your point of view? If so, is it a benign race or is > it serious? Well, I guess nobody is using that driver in mainline, or at least not with platforms that do system suspend. The suspend is supposed to call ucb1400_ts_stop(), not ucb1400_ts_start(), and resume is messed up as well. We need to fix it. Once it is done, then it should look better. The ucb->stopped can change in the middle of while loop, and that should cause the interrupt handler to stop running. The "stop" uses disable_irq() and thus will wait for the interrupt handler to finish before continuing. Thanks. -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
