From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>,
x86@kernel.org, Peter Zijlstra <peterz@infradead.org>,
Matt Rickard <matt@softrans.com.au>,
Stephen Boyd <sboyd@kernel.org>,
John Stultz <john.stultz@linaro.org>,
Florian Weimer <fweimer@redhat.com>,
"K. Y. Srinivasan" <kys@microsoft.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
devel@linuxdriverproject.org,
virtualization@lists.linux-foundation.org,
Paolo Bonzini <pbonzini@redhat.com>,
Arnd Bergmann <arnd@arndb.de>, Juergen Gross <jgross@suse.com>
Subject: [patch 08/11] x86/vdso: Replace the clockid switch case
Date: Fri, 14 Sep 2018 14:50:14 +0200 [thread overview]
Message-ID: <20180914125118.827005379@linutronix.de> (raw)
In-Reply-To: 20180914125006.349747096@linutronix.de
[-- Attachment #1: x86-vdso--Replace-the-clockid-switch-case.patch --]
[-- Type: text/plain, Size: 2114 bytes --]
Now that the time getter functions use the clockid as index into the
storage array for the base time access, the switch case can be replaced.
- Check for clockid >= MAX_CLOCKS and for negative clockid (CPU/FD) first
and call the fallback function right away.
- After establishing that clockid is < MAX_CLOCKS, convert the clockid to a
bitmask
- Check for the supported high resolution and coarse functions by anding
the bitmask of supported clocks and check whether a bit is set.
This completely avoids jump tables, reduces the number of conditionals and
makes the VDSO extensible for other clock ids.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/entry/vdso/vclock_gettime.c | 38 ++++++++++++++++-------------------
1 file changed, 18 insertions(+), 20 deletions(-)
--- a/arch/x86/entry/vdso/vclock_gettime.c
+++ b/arch/x86/entry/vdso/vclock_gettime.c
@@ -239,29 +239,27 @@ notrace static void do_coarse(clockid_t
notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
{
- switch (clock) {
- case CLOCK_REALTIME:
- if (do_hres(CLOCK_REALTIME, ts) == VCLOCK_NONE)
- goto fallback;
- break;
- case CLOCK_MONOTONIC:
- if (do_hres(CLOCK_MONOTONIC, ts) == VCLOCK_NONE)
- goto fallback;
- break;
- case CLOCK_REALTIME_COARSE:
- do_coarse(CLOCK_REALTIME_COARSE, ts);
- break;
- case CLOCK_MONOTONIC_COARSE:
- do_coarse(CLOCK_MONOTONIC_COARSE, ts);
- break;
- default:
- goto fallback;
- }
+ unsigned int msk;
+
+ /* Sort out negative (CPU/FD) and invalid clocks */
+ if (unlikely((unsigned int) clock >= MAX_CLOCKS))
+ return vdso_fallback_gettime(clock, ts);
- return 0;
-fallback:
+ /*
+ * Convert the clockid to a bitmask and use it to check which
+ * clocks are handled in the VDSO directly.
+ */
+ msk = 1U << clock;
+ if (likely(msk & VGTOD_HRES)) {
+ if (do_hres(clock, ts) != VCLOCK_NONE)
+ return 0;
+ } else if (msk & VGTOD_COARSE) {
+ do_coarse(clock, ts);
+ return 0;
+ }
return vdso_fallback_gettime(clock, ts);
}
+
int clock_gettime(clockid_t, struct timespec *)
__attribute__((weak, alias("__vdso_clock_gettime")));
next prev parent reply other threads:[~2018-09-14 12:52 UTC|newest]
Thread overview: 81+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-14 12:50 [patch 00/11] x86/vdso: Cleanups, simmplifications and CLOCK_TAI support Thomas Gleixner
2018-09-14 12:50 ` [patch 01/11] clocksource: Provide clocksource_arch_init() Thomas Gleixner
2018-09-14 12:50 ` [patch 02/11] x86/time: Implement clocksource_arch_init() Thomas Gleixner
2018-09-14 15:45 ` Vitaly Kuznetsov
2018-09-15 6:05 ` Thomas Gleixner
2018-09-14 12:50 ` [patch 03/11] x86/vdso: Enforce 64bit clocksource Thomas Gleixner
2018-09-14 12:50 ` [patch 04/11] x86/vdso: Use unsigned int consistently for vsyscall_gtod_data::seq Thomas Gleixner
2018-09-14 12:50 ` [patch 05/11] x86/vdso: Introduce and use vgtod_ts Thomas Gleixner
2018-09-14 12:50 ` [patch 06/11] x86/vdso: Collapse high resolution functions Thomas Gleixner
2018-09-14 12:50 ` [patch 07/11] x86/vdso: Collapse coarse functions Thomas Gleixner
2018-09-14 12:50 ` Thomas Gleixner [this message]
2018-09-14 12:50 ` [patch 09/11] x86/vdso: Simplify the invalid vclock case Thomas Gleixner
2018-09-17 19:25 ` Andy Lutomirski
2018-09-17 20:12 ` John Stultz
2018-09-18 7:52 ` Thomas Gleixner
2018-09-18 8:30 ` Peter Zijlstra
2018-09-18 8:52 ` Thomas Gleixner
2018-09-18 10:06 ` Thomas Gleixner
2018-09-18 10:41 ` Thomas Gleixner
2018-09-18 12:48 ` Peter Zijlstra
2018-09-18 13:23 ` Thomas Gleixner
2018-09-18 13:38 ` Peter Zijlstra
2018-09-18 15:52 ` Thomas Gleixner
2018-09-27 14:41 ` Thomas Gleixner
2018-09-18 14:01 ` Andy Lutomirski
2018-09-18 22:46 ` Thomas Gleixner
2018-09-18 23:03 ` Andy Lutomirski
2018-09-18 23:16 ` Thomas Gleixner
2018-09-27 14:36 ` Thomas Gleixner
2018-09-27 14:39 ` Andy Lutomirski
2018-09-19 9:08 ` Rasmus Villemoes
2018-09-19 13:29 ` Thomas Gleixner
2018-09-14 12:50 ` [patch 10/11] x86/vdso: Move cycle_last handling into the caller Thomas Gleixner
2018-09-14 15:26 ` Vitaly Kuznetsov
2018-09-14 12:50 ` [patch 11/11] x66/vdso: Add CLOCK_TAI support Thomas Gleixner
2018-09-14 14:04 ` Andy Lutomirski
2018-09-14 14:27 ` Thomas Gleixner
2018-09-14 14:59 ` Andy Lutomirski
2018-09-16 9:39 ` Thomas Gleixner
2018-09-14 12:56 ` [patch 00/11] x86/vdso: Cleanups, simmplifications and " Florian Weimer
2018-09-14 13:05 ` Thomas Gleixner
2018-09-14 13:06 ` Florian Weimer
2018-09-14 13:19 ` Thomas Gleixner
2018-09-14 13:09 ` Peter Zijlstra
2018-09-14 14:22 ` Arnd Bergmann
2018-09-17 13:00 ` Thomas Gleixner
2018-09-24 21:08 ` Arnd Bergmann
2018-10-03 5:15 ` Andy Lutomirski
2018-10-03 9:22 ` Vitaly Kuznetsov
2018-10-03 10:20 ` Andy Lutomirski
2018-10-03 12:01 ` Vitaly Kuznetsov
2018-10-03 14:20 ` Andy Lutomirski
2018-10-03 15:10 ` Thomas Gleixner
2018-10-03 16:18 ` Andy Lutomirski
2018-10-03 19:06 ` Marcelo Tosatti
2018-10-04 7:54 ` Vitaly Kuznetsov
2018-10-04 8:11 ` Peter Zijlstra
2018-10-04 14:00 ` Andy Lutomirski
2018-10-04 19:31 ` Peter Zijlstra
2018-10-04 20:05 ` Andy Lutomirski
2018-10-04 22:15 ` Andy Lutomirski
2018-10-06 20:27 ` Marcelo Tosatti
2018-10-06 22:28 ` Andy Lutomirski
2018-10-08 15:26 ` Marcelo Tosatti
2018-10-08 17:38 ` Andy Lutomirski
2018-10-08 19:36 ` Marcelo Tosatti
2018-10-09 20:09 ` Andy Lutomirski
2018-10-11 22:27 ` Marcelo Tosatti
2018-10-11 23:00 ` Andy Lutomirski
2018-10-15 13:39 ` Marcelo Tosatti
2018-10-06 20:49 ` Marcelo Tosatti
2018-10-04 12:00 ` Paolo Bonzini
2018-10-04 14:04 ` Andy Lutomirski
2018-10-05 21:18 ` Marcelo Tosatti
2018-10-03 19:00 ` Marcelo Tosatti
2018-10-03 19:05 ` [patch 00/11] x86/vdso: Cleanups, simmplifications and CLOCK_TAI support\ Marcelo Tosatti
2018-10-03 22:32 ` [patch 00/11] x86/vdso: Cleanups, simmplifications and CLOCK_TAI support Andy Lutomirski
2018-10-04 16:37 ` Marcelo Tosatti
2018-10-04 17:08 ` Andy Lutomirski
2018-10-04 17:28 ` Vitaly Kuznetsov
2018-10-04 20:32 ` Andy Lutomirski
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