From: Arul Jeniston <arul.jeniston@gmail.com>
To: viro@zeniv.linux.org.uk, tglx@linutronix.de
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
arul_mc@dell.com, ARUL JENISTON MC <arul.jeniston@gmail.com>
Subject: [PATCH] FS: timerfd: Fix unexpected return value of timerfd_read function.
Date: Fri, 16 Aug 2019 15:52:09 +0530 [thread overview]
Message-ID: <CACAVd4iXVH2U41msVKhT4GBGgE=2V2oXnOXkQUQKSSh72HMMmw@mail.gmail.com> (raw)
In-Reply-To: <20190816083246.169312-1-arul.jeniston@gmail.com>
'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@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
next prev parent reply other threads:[~2019-08-16 10:22 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-16 8:32 [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@gmail.com> arul.jeniston
2019-08-16 9:05 ` [PATCH] FS: timerfd: [Trimmed unreadable long subject line ] Thomas Gleixner
2019-08-16 10:22 ` Arul Jeniston [this message]
2019-08-16 10:45 ` [PATCH] FS: timerfd: Fix unexpected return value of timerfd_read function Thomas Gleixner
2019-08-16 16:55 ` Arul Jeniston
2019-08-16 17:00 ` Arul Jeniston
2019-08-16 21:17 ` Thomas Gleixner
[not found] ` <CACAVd4hT6QYtgtDsBcgy7c_s9WVBAH+1m0r5geBe7BUWJWYhbA@mail.gmail.com>
2019-08-17 19:23 ` Thomas Gleixner
2019-08-19 6:07 ` Arul Jeniston
2019-08-19 8:04 ` Thomas Gleixner
2019-08-19 14:25 ` Arul Jeniston
2019-08-19 14:52 ` Thomas Gleixner
2019-08-19 15:26 ` Arul Jeniston
2019-08-19 15:59 ` Thomas Gleixner
[not found] ` <CACAVd4iRN7=eq_B1+Yb-xcspU-Sg1dmMo_=VtLXXVPkjN1hY5Q@mail.gmail.com>
2019-08-19 18:29 ` Thomas Gleixner
2019-08-20 6:11 ` Arul Jeniston
2019-08-20 8:49 ` Thomas Gleixner
2019-08-20 9:42 ` Arul Jeniston
2019-09-05 8:48 ` Arul Jeniston
2019-09-05 15:34 ` Thomas Gleixner
2019-09-06 16:36 ` Arul Jeniston
2019-09-07 14:38 ` Thomas Gleixner
2019-11-05 5:01 ` Arul Jeniston
2019-11-05 10:01 ` Thomas Gleixner
2019-11-06 3:38 ` Arul Jeniston
2020-02-12 18:14 ` Arul Jeniston
2020-02-13 12:11 ` Thomas Gleixner
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