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Subject[tip: timers/core] posix-cpu-timers: Switch thread group sampling to array
The following commit has been merged into the timers/core branch of tip:

Commit-ID: b7be4ef1365dcb56fdffc6689e41058b23f5996d
Gitweb: https://git.kernel.org/tip/b7be4ef1365dcb56fdffc6689e41058b23f5996d
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Wed, 21 Aug 2019 21:09:16 +02:00
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Wed, 28 Aug 2019 11:50:39 +02:00

posix-cpu-timers: Switch thread group sampling to array

That allows more simplifications in various places.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lkml.kernel.org/r/20190821192921.988426956@linutronix.de

---
include/linux/sched/cputime.h | 2 +-
kernel/time/itimer.c | 11 +---
kernel/time/posix-cpu-timers.c | 104 +++++++++++++-------------------
3 files changed, 49 insertions(+), 68 deletions(-)

diff --git a/include/linux/sched/cputime.h b/include/linux/sched/cputime.h
index 2638fd0..eefa5df 100644
--- a/include/linux/sched/cputime.h
+++ b/include/linux/sched/cputime.h
@@ -61,7 +61,7 @@ extern void cputime_adjust(struct task_cputime *curr, struct prev_cputime *prev,
* Thread group CPU time accounting.
*/
void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times);
-void thread_group_sample_cputime(struct task_struct *tsk, struct task_cputime *times);
+void thread_group_sample_cputime(struct task_struct *tsk, u64 *samples);

/*
* The following are functions that support scheduler-internal time accounting.
diff --git a/kernel/time/itimer.c b/kernel/time/itimer.c
index ae04bc2..77f1e56 100644
--- a/kernel/time/itimer.c
+++ b/kernel/time/itimer.c
@@ -55,15 +55,10 @@ static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
val = it->expires;
interval = it->incr;
if (val) {
- struct task_cputime cputime;
- u64 t;
+ u64 t, samples[CPUCLOCK_MAX];

- thread_group_sample_cputime(tsk, &cputime);
- if (clock_id == CPUCLOCK_PROF)
- t = cputime.utime + cputime.stime;
- else
- /* CPUCLOCK_VIRT */
- t = cputime.utime;
+ thread_group_sample_cputime(tsk, samples);
+ t = samples[clock_id];

if (val < t)
/* about to fire */
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index 9ac601a..e62139a 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -225,22 +225,14 @@ static inline void __update_gt_cputime(atomic64_t *cputime, u64 sum_cputime)
}
}

-static void update_gt_cputime(struct task_cputime_atomic *cputime_atomic, struct task_cputime *sum)
+static void update_gt_cputime(struct task_cputime_atomic *cputime_atomic,
+ struct task_cputime *sum)
{
__update_gt_cputime(&cputime_atomic->utime, sum->utime);
__update_gt_cputime(&cputime_atomic->stime, sum->stime);
__update_gt_cputime(&cputime_atomic->sum_exec_runtime, sum->sum_exec_runtime);
}

-/* Sample task_cputime_atomic values in "atomic_timers", store results in "times". */
-static inline void sample_cputime_atomic(struct task_cputime *times,
- struct task_cputime_atomic *atomic_times)
-{
- times->utime = atomic64_read(&atomic_times->utime);
- times->stime = atomic64_read(&atomic_times->stime);
- times->sum_exec_runtime = atomic64_read(&atomic_times->sum_exec_runtime);
-}
-
/**
* thread_group_sample_cputime - Sample cputime for a given task
* @tsk: Task for which cputime needs to be started
@@ -252,20 +244,19 @@ static inline void sample_cputime_atomic(struct task_cputime *times,
*
* Updates @times with an uptodate sample of the thread group cputimes.
*/
-void thread_group_sample_cputime(struct task_struct *tsk,
- struct task_cputime *times)
+void thread_group_sample_cputime(struct task_struct *tsk, u64 *samples)
{
struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;

WARN_ON_ONCE(!cputimer->running);

- sample_cputime_atomic(times, &cputimer->cputime_atomic);
+ proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
}

/**
* thread_group_start_cputime - Start cputime and return a sample
* @tsk: Task for which cputime needs to be started
- * @iimes: Storage for time samples
+ * @samples: Storage for time samples
*
* The thread group cputime accouting is avoided when there are no posix
* CPU timers armed. Before starting a timer it's required to check whether
@@ -274,14 +265,14 @@ void thread_group_sample_cputime(struct task_struct *tsk,
*
* Updates @times with an uptodate sample of the thread group cputimes.
*/
-static void
-thread_group_start_cputime(struct task_struct *tsk, struct task_cputime *times)
+static void thread_group_start_cputime(struct task_struct *tsk, u64 *samples)
{
struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
- struct task_cputime sum;

/* Check if cputimer isn't running. This is accessed without locking. */
if (!READ_ONCE(cputimer->running)) {
+ struct task_cputime sum;
+
/*
* The POSIX timer interface allows for absolute time expiry
* values through the TIMER_ABSTIME flag, therefore we have
@@ -299,7 +290,15 @@ thread_group_start_cputime(struct task_struct *tsk, struct task_cputime *times)
*/
WRITE_ONCE(cputimer->running, true);
}
- sample_cputime_atomic(times, &cputimer->cputime_atomic);
+ proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
+}
+
+static void __thread_group_cputime(struct task_struct *tsk, u64 *samples)
+{
+ struct task_cputime ct;
+
+ thread_group_cputime(tsk, &ct);
+ store_samples(samples, ct.stime, ct.utime, ct.sum_exec_runtime);
}

/*
@@ -313,28 +312,18 @@ static u64 cpu_clock_sample_group(const clockid_t clkid, struct task_struct *p,
bool start)
{
struct thread_group_cputimer *cputimer = &p->signal->cputimer;
- struct task_cputime cputime;
+ u64 samples[CPUCLOCK_MAX];

if (!READ_ONCE(cputimer->running)) {
if (start)
- thread_group_start_cputime(p, &cputime);
+ thread_group_start_cputime(p, samples);
else
- thread_group_cputime(p, &cputime);
+ __thread_group_cputime(p, samples);
} else {
- sample_cputime_atomic(&cputime, &cputimer->cputime_atomic);
+ proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
}

- switch (clkid) {
- case CPUCLOCK_PROF:
- return cputime.utime + cputime.stime;
- case CPUCLOCK_VIRT:
- return cputime.utime;
- case CPUCLOCK_SCHED:
- return cputime.sum_exec_runtime;
- default:
- WARN_ON_ONCE(1);
- }
- return 0;
+ return samples[clkid];
}

static int posix_cpu_clock_get(const clockid_t clock, struct timespec64 *tp)
@@ -889,9 +878,7 @@ static void check_process_timers(struct task_struct *tsk,
{
struct signal_struct *const sig = tsk->signal;
struct posix_cputimer_base *base = sig->posix_cputimers.bases;
- u64 utime, ptime, virt_expires, prof_expires;
- u64 sum_sched_runtime, sched_expires;
- struct task_cputime cputime;
+ u64 virt_exp, prof_exp, sched_exp, samples[CPUCLOCK_MAX];
unsigned long soft;

/*
@@ -911,30 +898,29 @@ static void check_process_timers(struct task_struct *tsk,
* Collect the current process totals. Group accounting is active
* so the sample can be taken directly.
*/
- sample_cputime_atomic(&cputime, &sig->cputimer.cputime_atomic);
- utime = cputime.utime;
- ptime = utime + cputime.stime;
- sum_sched_runtime = cputime.sum_exec_runtime;
-
- prof_expires = check_timers_list(&base[CPUCLOCK_PROF].cpu_timers,
- firing, ptime);
- virt_expires = check_timers_list(&base[CPUCLOCK_VIRT].cpu_timers,
- firing, utime);
- sched_expires = check_timers_list(&base[CPUCLOCK_SCHED].cpu_timers,
- firing, sum_sched_runtime);
+ proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic, samples);
+
+ prof_exp = check_timers_list(&base[CPUCLOCK_PROF].cpu_timers,
+ firing, samples[CPUCLOCK_PROF]);
+ virt_exp = check_timers_list(&base[CPUCLOCK_VIRT].cpu_timers,
+ firing, samples[CPUCLOCK_VIRT]);
+ sched_exp = check_timers_list(&base[CPUCLOCK_SCHED].cpu_timers,
+ firing, samples[CPUCLOCK_SCHED]);

/*
* Check for the special case process timers.
*/
- check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_expires, ptime,
- SIGPROF);
- check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
- SIGVTALRM);
+ check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_exp,
+ samples[CPUCLOCK_PROF], SIGPROF);
+ check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_exp,
+ samples[CPUCLOCK_PROF], SIGVTALRM);
+
soft = task_rlimit(tsk, RLIMIT_CPU);
if (soft != RLIM_INFINITY) {
- unsigned long psecs = div_u64(ptime, NSEC_PER_SEC);
+ u64 softns, ptime = samples[CPUCLOCK_PROF];
unsigned long hard = task_rlimit_max(tsk, RLIMIT_CPU);
- u64 x;
+ unsigned long psecs = div_u64(ptime, NSEC_PER_SEC);
+
if (psecs >= hard) {
/*
* At the hard limit, we just die.
@@ -961,14 +947,14 @@ static void check_process_timers(struct task_struct *tsk,
sig->rlim[RLIMIT_CPU].rlim_cur = soft;
}
}
- x = soft * NSEC_PER_SEC;
- if (!prof_expires || x < prof_expires)
- prof_expires = x;
+ softns = soft * NSEC_PER_SEC;
+ if (!prof_exp || softns < prof_exp)
+ prof_exp = softns;
}

- base[CPUCLOCK_PROF].nextevt = prof_expires;
- base[CPUCLOCK_VIRT].nextevt = virt_expires;
- base[CPUCLOCK_SCHED].nextevt = sched_expires;
+ base[CPUCLOCK_PROF].nextevt = prof_exp;
+ base[CPUCLOCK_VIRT].nextevt = virt_exp;
+ base[CPUCLOCK_SCHED].nextevt = sched_exp;

if (expiry_cache_is_zero(&sig->posix_cputimers))
stop_process_timers(sig);
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