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Diffstat (limited to 'kernel/time/posix-cpu-timers.c')
-rw-r--r--kernel/time/posix-cpu-timers.c97
1 files changed, 59 insertions, 38 deletions
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index 0ac829b48..892e3dae0 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -196,39 +196,62 @@ static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
return 0;
}
-static void update_gt_cputime(struct task_cputime *a, struct task_cputime *b)
+/*
+ * Set cputime to sum_cputime if sum_cputime > cputime. Use cmpxchg
+ * to avoid race conditions with concurrent updates to cputime.
+ */
+static inline void __update_gt_cputime(atomic64_t *cputime, u64 sum_cputime)
{
- if (b->utime > a->utime)
- a->utime = b->utime;
+ u64 curr_cputime;
+retry:
+ curr_cputime = atomic64_read(cputime);
+ if (sum_cputime > curr_cputime) {
+ if (atomic64_cmpxchg(cputime, curr_cputime, sum_cputime) != curr_cputime)
+ goto retry;
+ }
+}
- if (b->stime > a->stime)
- a->stime = b->stime;
+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);
+}
- if (b->sum_exec_runtime > a->sum_exec_runtime)
- a->sum_exec_runtime = b->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);
}
void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
{
struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
struct task_cputime sum;
- unsigned long flags;
- if (!cputimer->running) {
+ /* Check if cputimer isn't running. This is accessed without locking. */
+ if (!READ_ONCE(cputimer->running)) {
/*
* The POSIX timer interface allows for absolute time expiry
* values through the TIMER_ABSTIME flag, therefore we have
- * to synchronize the timer to the clock every time we start
- * it.
+ * to synchronize the timer to the clock every time we start it.
*/
thread_group_cputime(tsk, &sum);
- raw_spin_lock_irqsave(&cputimer->lock, flags);
- cputimer->running = 1;
- update_gt_cputime(&cputimer->cputime, &sum);
- } else
- raw_spin_lock_irqsave(&cputimer->lock, flags);
- *times = cputimer->cputime;
- raw_spin_unlock_irqrestore(&cputimer->lock, flags);
+ update_gt_cputime(&cputimer->cputime_atomic, &sum);
+
+ /*
+ * We're setting cputimer->running without a lock. Ensure
+ * this only gets written to in one operation. We set
+ * running after update_gt_cputime() as a small optimization,
+ * but barriers are not required because update_gt_cputime()
+ * can handle concurrent updates.
+ */
+ WRITE_ONCE(cputimer->running, 1);
+ }
+ sample_cputime_atomic(times, &cputimer->cputime_atomic);
}
/*
@@ -425,7 +448,7 @@ static void cleanup_timers(struct list_head *head)
*/
void posix_cpu_timers_exit(struct task_struct *tsk)
{
- add_device_randomness((const void*) &tsk_seruntime(tsk),
+ add_device_randomness((const void*) &tsk->se.sum_exec_runtime,
sizeof(unsigned long long));
cleanup_timers(tsk->cpu_timers);
@@ -582,7 +605,8 @@ bool posix_cpu_timers_can_stop_tick(struct task_struct *tsk)
if (!task_cputime_zero(&tsk->cputime_expires))
return false;
- if (tsk->signal->cputimer.running)
+ /* Check if cputimer is running. This is accessed without locking. */
+ if (READ_ONCE(tsk->signal->cputimer.running))
return false;
return true;
@@ -847,18 +871,18 @@ static void check_thread_timers(struct task_struct *tsk,
tsk_expires->virt_exp = expires_to_cputime(expires);
tsk_expires->sched_exp = check_timers_list(++timers, firing,
- tsk_seruntime(tsk));
+ tsk->se.sum_exec_runtime);
/*
* Check for the special case thread timers.
*/
- soft = ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_cur);
+ soft = READ_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_cur);
if (soft != RLIM_INFINITY) {
unsigned long hard =
- ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_max);
+ READ_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_max);
if (hard != RLIM_INFINITY &&
- tsk_rttimeout(tsk) > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
+ tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
/*
* At the hard limit, we just die.
* No need to calculate anything else now.
@@ -866,7 +890,7 @@ static void check_thread_timers(struct task_struct *tsk,
__group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
return;
}
- if (tsk_rttimeout(tsk) > DIV_ROUND_UP(soft, USEC_PER_SEC/HZ)) {
+ if (tsk->rt.timeout > DIV_ROUND_UP(soft, USEC_PER_SEC/HZ)) {
/*
* At the soft limit, send a SIGXCPU every second.
*/
@@ -882,14 +906,12 @@ static void check_thread_timers(struct task_struct *tsk,
}
}
-static void stop_process_timers(struct signal_struct *sig)
+static inline void stop_process_timers(struct signal_struct *sig)
{
struct thread_group_cputimer *cputimer = &sig->cputimer;
- unsigned long flags;
- raw_spin_lock_irqsave(&cputimer->lock, flags);
- cputimer->running = 0;
- raw_spin_unlock_irqrestore(&cputimer->lock, flags);
+ /* Turn off cputimer->running. This is done without locking. */
+ WRITE_ONCE(cputimer->running, 0);
}
static u32 onecputick;
@@ -958,11 +980,11 @@ static void check_process_timers(struct task_struct *tsk,
SIGPROF);
check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
SIGVTALRM);
- soft = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
+ soft = READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
if (soft != RLIM_INFINITY) {
unsigned long psecs = cputime_to_secs(ptime);
unsigned long hard =
- ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_max);
+ READ_ONCE(sig->rlim[RLIMIT_CPU].rlim_max);
cputime_t x;
if (psecs >= hard) {
/*
@@ -1103,7 +1125,7 @@ static inline int fastpath_timer_check(struct task_struct *tsk)
struct task_cputime task_sample = {
.utime = utime,
.stime = stime,
- .sum_exec_runtime = tsk_seruntime(tsk)
+ .sum_exec_runtime = tsk->se.sum_exec_runtime
};
if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
@@ -1111,12 +1133,11 @@ static inline int fastpath_timer_check(struct task_struct *tsk)
}
sig = tsk->signal;
- if (sig->cputimer.running) {
+ /* Check if cputimer is running. This is accessed without locking. */
+ if (READ_ONCE(sig->cputimer.running)) {
struct task_cputime group_sample;
- raw_spin_lock(&sig->cputimer.lock);
- group_sample = sig->cputimer.cputime;
- raw_spin_unlock(&sig->cputimer.lock);
+ sample_cputime_atomic(&group_sample, &sig->cputimer.cputime_atomic);
if (task_cputime_expired(&group_sample, &sig->cputime_expires))
return 1;
@@ -1157,7 +1178,7 @@ void run_posix_cpu_timers(struct task_struct *tsk)
* If there are any active process wide timers (POSIX 1.b, itimers,
* RLIMIT_CPU) cputimer must be running.
*/
- if (tsk->signal->cputimer.running)
+ if (READ_ONCE(tsk->signal->cputimer.running))
check_process_timers(tsk, &firing);
/*
generated by cgit v1.2.3-54-g00ecf (git 2.45.2) at 2024-11-20 00:15:03 +0000