'hrtimer_forward_now()' returns zero due to bigger backward time drift. This causes timerfd_read to return 0. As per man page, read on timerfd is not expected to return 0. This problem is well explained in https://lkml.org/lkml/2019/7/31/442 . This patch fixes this problem. Signed-off-by: Arul Jeniston <arul.jeniston@xxxxxxxxx> --- fs/timerfd.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/fs/timerfd.c b/fs/timerfd.c index 6a6fc8aa1de7..f5094e070e9a 100644 --- a/fs/timerfd.c +++ b/fs/timerfd.c @@ -284,8 +284,16 @@ static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count, &ctx->t.alarm, ctx->tintv) - 1; alarm_restart(&ctx->t.alarm); } else { - ticks += hrtimer_forward_now(&ctx->t.tmr, - ctx->tintv) - 1; + u64 nooftimeo = hrtimer_forward_now(&ctx->t.tmr, + ctx->tintv); + /* + * ticks shouldn't become zero at this point. + * Ignore if hrtimer_forward_now returns 0 + * due to larger backward time drift. + */ + if (likely(nooftimeo)) { + ticks += nooftimeo - 1; + } hrtimer_restart(&ctx->t.tmr); } } -- 2.11.0
