From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>, Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
John Stultz <john.stultz@linaro.org>,
Frederic Weisbecker <frederic@kernel.org>,
Anna-Maria Behnsen <anna-maria@linutronix.de>,
Christoph Hellwig <hch@lst.de>
Subject: [patch V2 32/38] posix-cpu-timers: Get rid of zero checks
Date: Wed, 21 Aug 2019 21:09:19 +0200 [thread overview]
Message-ID: <20190821192922.275086128@linutronix.de> (raw)
In-Reply-To: 20190821190847.665673890@linutronix.de
Deactivation of the expiry cache is done by setting all clock caches to
0. That requires to have a check for zero in all places which update the
expiry cache:
if (cache == 0 || new < cache)
cache = new;
Use U64_MAX as the deactivated value, which allows to remove the zero
checks when updating the cache and reduces it to the obvious check:
if (new < cache)
cache = new;
This also removes the weird workaround in do_prlimit() which was required
to convert a RLIMIT_CPU value of 0 (immediate expiry) to 1 because handing
in 0 to the posix CPU timer code would have effectively disarmed it.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
V2: Adopt to the per clock base struct and cleanup the rlimit setter code.
---
include/linux/posix-timers.h | 7 +++++--
kernel/sys.c | 9 ---------
kernel/time/posix-cpu-timers.c | 36 ++++++++++++++----------------------
3 files changed, 19 insertions(+), 33 deletions(-)
--- a/include/linux/posix-timers.h
+++ b/include/linux/posix-timers.h
@@ -86,7 +86,9 @@ struct posix_cputimers {
static inline void posix_cputimers_init(struct posix_cputimers *pct)
{
- memset(pct->bases, 0, sizeof(pct->bases));
+ pct->bases[0].nextevt = U64_MAX;
+ pct->bases[1].nextevt = U64_MAX;
+ pct->bases[2].nextevt = U64_MAX;
INIT_LIST_HEAD(&pct->bases[0].cpu_timers);
INIT_LIST_HEAD(&pct->bases[1].cpu_timers);
INIT_LIST_HEAD(&pct->bases[2].cpu_timers);
@@ -102,7 +104,8 @@ static inline void posix_cputimers_rt_wa
/* Init task static initializer */
#define INIT_CPU_TIMERBASE(b) { \
- .cpu_timers = LIST_HEAD_INIT(b.cpu_timers), \
+ .nextevt = U64_MAX, \
+ .cpu_timers = LIST_HEAD_INIT(b.cpu_timers), \
}
#define INIT_CPU_TIMERBASES(b) { \
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1557,15 +1557,6 @@ int do_prlimit(struct task_struct *tsk,
retval = -EPERM;
if (!retval)
retval = security_task_setrlimit(tsk, resource, new_rlim);
- if (resource == RLIMIT_CPU && new_rlim->rlim_cur == 0) {
- /*
- * The caller is asking for an immediate RLIMIT_CPU
- * expiry. But we use the zero value to mean "it was
- * never set". So let's cheat and make it one second
- * instead
- */
- new_rlim->rlim_cur = 1;
- }
}
if (!retval) {
if (old_rlim)
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -122,11 +122,12 @@ static void bump_cpu_timer(struct k_itim
}
}
-static inline bool expiry_cache_is_zero(const struct posix_cputimers *pct)
+/* Check whether all cache entries contain U64_MAX, i.e. eternal expiry time */
+static inline bool expiry_cache_is_inactive(const struct posix_cputimers *pct)
{
- return !(pct->bases[CPUCLOCK_PROF].nextevt |
- pct->bases[CPUCLOCK_VIRT].nextevt |
- pct->bases[CPUCLOCK_SCHED].nextevt);
+ return !(~pct->bases[CPUCLOCK_PROF].nextevt |
+ ~pct->bases[CPUCLOCK_VIRT].nextevt |
+ ~pct->bases[CPUCLOCK_SCHED].nextevt);
}
static int
@@ -442,11 +443,6 @@ void posix_cpu_timers_exit_group(struct
cleanup_timers(&tsk->signal->posix_cputimers);
}
-static inline int expires_gt(u64 expires, u64 new_exp)
-{
- return expires == 0 || expires > new_exp;
-}
-
/*
* Insert the timer on the appropriate list before any timers that
* expire later. This must be called with the sighand lock held.
@@ -483,7 +479,7 @@ static void arm_timer(struct k_itimer *t
* for process timers we share expiration cache with itimers
* and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
*/
- if (expires_gt(base->nextevt, newexp))
+ if (newexp < base->nextevt)
base->nextevt = newexp;
if (CPUCLOCK_PERTHREAD(timer->it_clock))
@@ -753,7 +749,7 @@ check_timers_list(struct list_head *time
list_move_tail(&t->entry, firing);
}
- return 0;
+ return U64_MAX;
}
static inline void check_dl_overrun(struct task_struct *tsk)
@@ -779,11 +775,7 @@ static void check_thread_timers(struct t
if (dl_task(tsk))
check_dl_overrun(tsk);
- /*
- * If the expiry cache is zero, then there are no active per thread
- * CPU timers.
- */
- if (expiry_cache_is_zero(&tsk->posix_cputimers))
+ if (expiry_cache_is_inactive(&tsk->posix_cputimers))
return;
task_cputime(tsk, &utime, &stime);
@@ -833,7 +825,7 @@ static void check_thread_timers(struct t
}
}
- if (expiry_cache_is_zero(&tsk->posix_cputimers))
+ if (expiry_cache_is_inactive(&tsk->posix_cputimers))
tick_dep_clear_task(tsk, TICK_DEP_BIT_POSIX_TIMER);
}
@@ -864,7 +856,7 @@ static void check_cpu_itimer(struct task
__group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
}
- if (it->expires && (!*expires || it->expires < *expires))
+ if (it->expires && it->expires < *expires)
*expires = it->expires;
}
@@ -948,7 +940,7 @@ static void check_process_timers(struct
}
}
softns = soft * NSEC_PER_SEC;
- if (!prof_exp || softns < prof_exp)
+ if (softns < prof_exp)
prof_exp = softns;
}
@@ -956,7 +948,7 @@ static void check_process_timers(struct
base[CPUCLOCK_VIRT].nextevt = virt_exp;
base[CPUCLOCK_SCHED].nextevt = sched_exp;
- if (expiry_cache_is_zero(&sig->posix_cputimers))
+ if (expiry_cache_is_inactive(&sig->posix_cputimers))
stop_process_timers(sig);
sig->cputimer.checking_timer = false;
@@ -1055,7 +1047,7 @@ static inline bool fastpath_timer_check(
{
struct signal_struct *sig;
- if (!expiry_cache_is_zero(&tsk->posix_cputimers)) {
+ if (!expiry_cache_is_inactive(&tsk->posix_cputimers)) {
u64 samples[CPUCLOCK_MAX];
task_sample_cputime(tsk, samples);
@@ -1199,7 +1191,7 @@ void set_process_cpu_timer(struct task_s
* Update expiration cache if this is the earliest timer. CPUCLOCK_PROF
* expiry cache is also used by RLIMIT_CPU!.
*/
- if (expires_gt(*nextevt, *newval))
+ if (*newval < *nextevt)
*nextevt = *newval;
tick_dep_set_signal(tsk->signal, TICK_DEP_BIT_POSIX_TIMER);
next prev parent reply other threads:[~2019-08-21 19:31 UTC|newest]
Thread overview: 137+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-21 19:08 [patch V2 00/38] posix-cpu-timers: Cleanup and consolidation Thomas Gleixner
2019-08-21 19:08 ` [patch V2 01/38] posix-cpu-timers: Provide task validation functions Thomas Gleixner
2019-08-21 22:33 ` Frederic Weisbecker
2019-08-21 23:03 ` Frederic Weisbecker
2019-08-23 15:33 ` Thomas Gleixner
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:08 ` [patch V2 02/38] posix-cpu-timers: Use common permission check in posix_cpu_clock_get() Thomas Gleixner
2019-08-21 23:40 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-29 11:00 ` kbuild test robot
2019-08-29 11:21 ` Thomas Gleixner
2019-08-30 1:08 ` [kbuild-all] " Philip Li
2019-08-29 11:23 ` kbuild test robot
2019-08-21 19:08 ` [patch V2 03/38] posix-cpu-timers: Use common permission check in posix_cpu_timer_create() Thomas Gleixner
2019-08-21 23:49 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:08 ` [patch V2 04/38] posix-cpu-timers: Provide quick sample function for itimer Thomas Gleixner
2019-08-22 12:13 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:08 ` [patch V2 05/38] itimers: Use quick sample function Thomas Gleixner
2019-08-22 12:15 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-29 23:47 ` kbuild test robot
2019-08-30 6:01 ` Thomas Gleixner
2019-08-21 19:08 ` [patch V2 06/38] posix-cpu-timers: Sample directly in timer check Thomas Gleixner
2019-08-22 12:30 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:08 ` [patch V2 07/38] posix-cpu-timers: Rename thread_group_cputimer() and make it static Thomas Gleixner
2019-08-22 12:41 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:08 ` [patch V2 08/38] posix-cpu-timers: Consolidate thread group sample code Thomas Gleixner
2019-08-22 13:49 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:08 ` [patch V2 09/38] posix-cpu-timers: Use clock ID in posix_cpu_timer_set() Thomas Gleixner
2019-08-22 13:58 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:08 ` [patch V2 10/38] posix-cpu-timers: Use clock ID in posix_cpu_timer_get() Thomas Gleixner
2019-08-22 14:07 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:08 ` [patch V2 11/38] posix-cpu-timers: Use clock ID in posix_cpu_timer_rearm() Thomas Gleixner
2019-08-22 14:12 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:08 ` [patch V2 12/38] posix-cpu-timers: Remove pointless return value check Thomas Gleixner
2019-08-22 14:15 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 13/38] posix-cpu-timers: Simplify sample functions Thomas Gleixner
2019-08-22 14:20 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 14/38] posix-cpu-timers: Get rid of pointer indirection Thomas Gleixner
2019-08-22 14:41 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 15/38] posix-cpu-timers: Sample task times once in expiry check Thomas Gleixner
2019-08-22 15:00 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 16/38] posix-cpu-timers: Move prof/virt_ticks into caller Thomas Gleixner
2019-08-22 15:05 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 17/38] posix-cpu-timers: Create a container struct Thomas Gleixner
2019-08-22 15:32 ` Frederic Weisbecker
2019-08-23 15:34 ` Thomas Gleixner
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 19/38] posix-cpu-timers: Move expiry cache into struct posix_cputimers Thomas Gleixner
2019-08-22 16:29 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 20/38] posix-cpu-timers: Provide array based access to expiry cache Thomas Gleixner
2019-08-23 17:33 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 21/38] posix-cpu-timers: Simplify timer queueing Thomas Gleixner
2019-08-23 17:51 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 22/38] posix-cpu-timers: Simplify set_process_cpu_timer() Thomas Gleixner
2019-08-23 18:00 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 23/38] posix-cpu-timers: Switch check_*_timers() to array cache Thomas Gleixner
2019-08-23 18:13 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 24/38] posix-cpu-timers: Remove the odd field rename defines Thomas Gleixner
2019-08-23 18:36 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 25/38] posix-cpu-timers: Provide array based sample functions Thomas Gleixner
2019-08-23 22:08 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 26/38] posix-cpu-timers: Make expiry checks array based Thomas Gleixner
2019-08-23 22:44 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 27/38] posix-cpu-timers: Remove cputime_expires Thomas Gleixner
2019-08-23 22:50 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 28/38] posix-cpu-timers: Restructure expiry array Thomas Gleixner
2019-08-26 16:32 ` Frederic Weisbecker
2019-08-26 18:16 ` Thomas Gleixner
2019-08-26 18:22 ` [patch V3 " Thomas Gleixner
2019-08-26 19:45 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-26 21:06 ` [patch V2 28/38] " Frederic Weisbecker
2019-08-26 21:46 ` Thomas Gleixner
2019-08-21 19:09 ` [patch V2 29/38] posix-cpu-timers: Switch thread group sampling to array Thomas Gleixner
2019-08-26 21:12 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 30/38] posix-cpu-timers: Respect INFINITY for hard RTTIME limit Thomas Gleixner
2019-08-26 21:19 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 31/38] rlimit: Rewrite non-sensical RLIMIT_CPU comment Thomas Gleixner
2019-08-26 21:41 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` Thomas Gleixner [this message]
2019-08-26 21:57 ` [patch V2 32/38] posix-cpu-timers: Get rid of zero checks Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 33/38] posix-cpu-timers: Consolidate timer expiry further Thomas Gleixner
2019-08-26 22:29 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 34/38] posix-cpu-timers: Get rid of 64bit divisions Thomas Gleixner
2019-08-26 22:51 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 35/38] posix-cpu-timers: Remove pointless comparisons Thomas Gleixner
2019-08-26 22:59 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 36/38] posix-cpu-timers: Deduplicate rlimit handling Thomas Gleixner
2019-08-26 23:13 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 37/38] posix-cpu-timers: Move state tracking to struct posix_cputimers Thomas Gleixner
2019-08-26 23:28 ` Frederic Weisbecker
2019-08-26 23:33 ` Thomas Gleixner
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-21 19:09 ` [patch V2 38/38] posix-cpu-timers: Utilize timerqueue for storage Thomas Gleixner
2019-08-27 0:48 ` Frederic Weisbecker
2019-08-27 6:08 ` Thomas Gleixner
2019-08-27 13:17 ` Frederic Weisbecker
2019-08-27 13:46 ` Thomas Gleixner
2019-08-27 19:31 ` [patch V3 " Thomas Gleixner
2019-08-27 22:23 ` Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
2019-08-22 0:54 ` [patch V2 00/38] posix-cpu-timers: Cleanup and consolidation Christoph Hellwig
2019-08-22 1:02 ` Frederic Weisbecker
2019-08-22 1:02 ` Christoph Hellwig
[not found] ` <20190821192920.909530418@linutronix.de>
2019-08-22 16:06 ` [patch V2 18/38] sched: Move struct task_cputime to types.h Frederic Weisbecker
2019-08-28 10:16 ` [tip: timers/core] " tip-bot2 for Thomas Gleixner
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=20190821192922.275086128@linutronix.de \
--to=tglx@linutronix.de \
--cc=anna-maria@linutronix.de \
--cc=frederic@kernel.org \
--cc=hch@lst.de \
--cc=john.stultz@linaro.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=oleg@redhat.com \
--cc=peterz@infradead.org \
/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).