On Friday 23 October 2015 17:12:38 Pingbo Wen wrote: > On Monday, October 19, 2015 04:58 PM, Arnd Bergmann wrote: > >> - do_gettimeofday(&tv); > >> - tv.tv_usec += USEC_PER_SEC * (tv.tv_sec - mlc->instart.tv_sec); > >> - tv.tv_usec -= mlc->instart.tv_usec; > >> - if (tv.tv_usec >= mlc->intimeout) goto sched; > >> - tv.tv_usec = (mlc->intimeout - tv.tv_usec) * HZ / USEC_PER_SEC; > >> - if (!tv.tv_usec) goto sched; > >> - mod_timer(&hil_mlcs_kicker, jiffies + tv.tv_usec); > >> + ktime_get_ts64(&ts64); > >> + ts64.tv_nsec += NSEC_PER_SEC * > >> + (ts64.tv_sec - mlc->instart.tv_sec); > >> + ts64.tv_nsec -= mlc->instart.tv_nsec; > > > > tv_nsec will overflow here for any timeout over 4.3 seconds, where it > > used to overflow after 4294 seconds. This is almost certainly a bug. > > > > You could work around that by using ktime_get_ns() to get a nanosecond > > value right away, but a 64-bit number is more expensive to convert to > > jiffies. > > You are right, I didn't notice that tv_nsec is a 32bit variable. Maybe > we should use ktime_t here, so that handling sec and nsec separately is > needless. > > Using jiffies here will need to take more codes to handle jiffies overflow > carefully. I think coverting 64bit number to jiffies is the price we must > take, if we use 64bit version here. Handling the jiffies overflow is trivially done through the time_before() and time_after() helpers, like start = jiffies; ... now = jiffies; timeout = start + HZ * timeout_usec / USEC_PER_SEC; if (time_after(now, start + timeout_jiffies) timeout(); else mod_timer(timer, start + timeout_jiffies); The time_after function works because unsigned overflow is well-defined in C (unlike signed overflow). As a side-note, please take the time to delete any lines from the original mail that you are not referencing when you reply. Arnd -- 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
