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Subject[PATCH] FS: timerfd: Fix unexpected return value of timerfd_read function. '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
Date
From: ARUL JENISTON MC <arul.jeniston@gmail.com>

---
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
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