From: tip-bot for Geert Uytterhoeven <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: arnd@arndb.de, john.stultz@linaro.org, geert@linux-m68k.org,
sboyd@kernel.org, tglx@linutronix.de,
linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@kernel.org
Subject: [tip:timers/urgent] time: Make sure jiffies_to_msecs() preserves non-zero time periods
Date: Fri, 22 Jun 2018 08:51:52 -0700 [thread overview]
Message-ID: <tip-abcbcb80cd09cd40f2089d912764e315459b71f7@git.kernel.org> (raw)
In-Reply-To: <20180622143357.7495-1-geert@linux-m68k.org>
Commit-ID: abcbcb80cd09cd40f2089d912764e315459b71f7
Gitweb: https://git.kernel.org/tip/abcbcb80cd09cd40f2089d912764e315459b71f7
Author: Geert Uytterhoeven <geert@linux-m68k.org>
AuthorDate: Fri, 22 Jun 2018 16:33:57 +0200
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Fri, 22 Jun 2018 17:48:36 +0200
time: Make sure jiffies_to_msecs() preserves non-zero time periods
For the common cases where 1000 is a multiple of HZ, or HZ is a multiple of
1000, jiffies_to_msecs() never returns zero when passed a non-zero time
period.
However, if HZ > 1000 and not an integer multiple of 1000 (e.g. 1024 or
1200, as used on alpha and DECstation), jiffies_to_msecs() may return zero
for small non-zero time periods. This may break code that relies on
receiving back a non-zero value.
jiffies_to_usecs() does not need such a fix: one jiffy can only be less
than one µs if HZ > 1000000, and such large values of HZ are already
rejected at build time, twice:
- include/linux/jiffies.h does #error if HZ >= 12288,
- kernel/time/time.c has BUILD_BUG_ON(HZ > USEC_PER_SEC).
Broken since forever.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: linux-alpha@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20180622143357.7495-1-geert@linux-m68k.org
---
kernel/time/time.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/kernel/time/time.c b/kernel/time/time.c
index 6fa99213fc72..2b41e8e2d31d 100644
--- a/kernel/time/time.c
+++ b/kernel/time/time.c
@@ -28,6 +28,7 @@
*/
#include <linux/export.h>
+#include <linux/kernel.h>
#include <linux/timex.h>
#include <linux/capability.h>
#include <linux/timekeeper_internal.h>
@@ -314,9 +315,10 @@ unsigned int jiffies_to_msecs(const unsigned long j)
return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
#else
# if BITS_PER_LONG == 32
- return (HZ_TO_MSEC_MUL32 * j) >> HZ_TO_MSEC_SHR32;
+ return (HZ_TO_MSEC_MUL32 * j + (1ULL << HZ_TO_MSEC_SHR32) - 1) >>
+ HZ_TO_MSEC_SHR32;
# else
- return (j * HZ_TO_MSEC_NUM) / HZ_TO_MSEC_DEN;
+ return DIV_ROUND_UP(j * HZ_TO_MSEC_NUM, HZ_TO_MSEC_DEN);
# endif
#endif
}
prev parent reply other threads:[~2018-06-22 15:52 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-22 14:33 [PATCH v3] time: Make sure jiffies_to_msecs() preserves non-zero time periods Geert Uytterhoeven
2018-06-22 15:51 ` tip-bot for Geert Uytterhoeven [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=tip-abcbcb80cd09cd40f2089d912764e315459b71f7@git.kernel.org \
--to=tipbot@zytor.com \
--cc=arnd@arndb.de \
--cc=geert@linux-m68k.org \
--cc=hpa@zytor.com \
--cc=john.stultz@linaro.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-tip-commits@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=sboyd@kernel.org \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).