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Message-Id: <20190816083246.169312-1-arul.jeniston@gmail.com>
Date: Fri, 16 Aug 2019 01:32:46 -0700
From: arul.jeniston@...il.com
To: viro@...iv.linux.org.uk, tglx@...utronix.de
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
arul_mc@...l.com, ARUL JENISTON MC <arul.jeniston@...il.com>
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 patch fixes this problem. Signed-off-by: Arul Jeniston <arul.jeniston@...il.com>
From: ARUL JENISTON MC <arul.jeniston@...il.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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