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authorFrank Mayhar <fmayhar@google.com>2008-09-12 09:54:39 -0700
committerIngo Molnar <mingo@elte.hu>2008-09-23 13:38:44 +0200
commitbb34d92f643086d546b49cef680f6f305ed84414 (patch)
tree275887040c96971e133fa20d99517c1fcea76415 /kernel/posix-cpu-timers.c
parent5ce73a4a5a4893a1aa4cdeed1b1a5a6de42c43b6 (diff)
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timers: fix itimer/many thread hang, v2
This is the second resubmission of the posix timer rework patch, posted a few days ago. This includes the changes from the previous resubmittion, which addressed Oleg Nesterov's comments, removing the RCU stuff from the patch and un-inlining the thread_group_cputime() function for SMP. In addition, per Ingo Molnar it simplifies the UP code, consolidating much of it with the SMP version and depending on lower-level SMP/UP handling to take care of the differences. It also cleans up some UP compile errors, moves the scheduler stats-related macros into kernel/sched_stats.h, cleans up a merge error in kernel/fork.c and has a few other minor fixes and cleanups as suggested by Oleg and Ingo. Thanks for the review, guys. Signed-off-by: Frank Mayhar <fmayhar@google.com> Cc: Roland McGrath <roland@redhat.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/posix-cpu-timers.c')
-rw-r--r--kernel/posix-cpu-timers.c153
1 files changed, 64 insertions, 89 deletions
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 9a7ea049fcd..153dcb2639c 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -7,50 +7,46 @@
#include <linux/errno.h>
#include <linux/math64.h>
#include <asm/uaccess.h>
+#include <linux/kernel_stat.h>
-#ifdef CONFIG_SMP
/*
- * Allocate the thread_group_cputime structure appropriately for SMP kernels
- * and fill in the current values of the fields. Called from copy_signal()
- * via thread_group_cputime_clone_thread() when adding a second or subsequent
+ * Allocate the thread_group_cputime structure appropriately and fill in the
+ * current values of the fields. Called from copy_signal() via
+ * thread_group_cputime_clone_thread() when adding a second or subsequent
* thread to a thread group. Assumes interrupts are enabled when called.
*/
-int thread_group_cputime_alloc_smp(struct task_struct *tsk)
+int thread_group_cputime_alloc(struct task_struct *tsk)
{
struct signal_struct *sig = tsk->signal;
struct task_cputime *cputime;
/*
* If we have multiple threads and we don't already have a
- * per-CPU task_cputime struct, allocate one and fill it in with
- * the times accumulated so far.
+ * per-CPU task_cputime struct (checked in the caller), allocate
+ * one and fill it in with the times accumulated so far. We may
+ * race with another thread so recheck after we pick up the sighand
+ * lock.
*/
- if (sig->cputime.totals)
- return 0;
cputime = alloc_percpu(struct task_cputime);
if (cputime == NULL)
return -ENOMEM;
- read_lock(&tasklist_lock);
spin_lock_irq(&tsk->sighand->siglock);
if (sig->cputime.totals) {
spin_unlock_irq(&tsk->sighand->siglock);
- read_unlock(&tasklist_lock);
free_percpu(cputime);
return 0;
}
sig->cputime.totals = cputime;
- cputime = per_cpu_ptr(sig->cputime.totals, get_cpu());
+ cputime = per_cpu_ptr(sig->cputime.totals, smp_processor_id());
cputime->utime = tsk->utime;
cputime->stime = tsk->stime;
cputime->sum_exec_runtime = tsk->se.sum_exec_runtime;
- put_cpu_no_resched();
spin_unlock_irq(&tsk->sighand->siglock);
- read_unlock(&tasklist_lock);
return 0;
}
/**
- * thread_group_cputime_smp - Sum the thread group time fields across all CPUs.
+ * thread_group_cputime - Sum the thread group time fields across all CPUs.
*
* @tsk: The task we use to identify the thread group.
* @times: task_cputime structure in which we return the summed fields.
@@ -58,7 +54,7 @@ int thread_group_cputime_alloc_smp(struct task_struct *tsk)
* Walk the list of CPUs to sum the per-CPU time fields in the thread group
* time structure.
*/
-void thread_group_cputime_smp(
+void thread_group_cputime(
struct task_struct *tsk,
struct task_cputime *times)
{
@@ -83,8 +79,6 @@ void thread_group_cputime_smp(
}
}
-#endif /* CONFIG_SMP */
-
/*
* Called after updating RLIMIT_CPU to set timer expiration if necessary.
*/
@@ -300,7 +294,7 @@ static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
cpu->cpu = virt_ticks(p);
break;
case CPUCLOCK_SCHED:
- cpu->sched = task_sched_runtime(p);
+ cpu->sched = p->se.sum_exec_runtime + task_delta_exec(p);
break;
}
return 0;
@@ -309,16 +303,15 @@ static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
/*
* Sample a process (thread group) clock for the given group_leader task.
* Must be called with tasklist_lock held for reading.
- * Must be called with tasklist_lock held for reading, and p->sighand->siglock.
*/
-static int cpu_clock_sample_group_locked(unsigned int clock_idx,
- struct task_struct *p,
- union cpu_time_count *cpu)
+static int cpu_clock_sample_group(const clockid_t which_clock,
+ struct task_struct *p,
+ union cpu_time_count *cpu)
{
struct task_cputime cputime;
thread_group_cputime(p, &cputime);
- switch (clock_idx) {
+ switch (which_clock) {
default:
return -EINVAL;
case CPUCLOCK_PROF:
@@ -328,29 +321,12 @@ static int cpu_clock_sample_group_locked(unsigned int clock_idx,
cpu->cpu = cputime.utime;
break;
case CPUCLOCK_SCHED:
- cpu->sched = thread_group_sched_runtime(p);
+ cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
break;
}
return 0;
}
-/*
- * Sample a process (thread group) clock for the given group_leader task.
- * Must be called with tasklist_lock held for reading.
- */
-static int cpu_clock_sample_group(const clockid_t which_clock,
- struct task_struct *p,
- union cpu_time_count *cpu)
-{
- int ret;
- unsigned long flags;
- spin_lock_irqsave(&p->sighand->siglock, flags);
- ret = cpu_clock_sample_group_locked(CPUCLOCK_WHICH(which_clock), p,
- cpu);
- spin_unlock_irqrestore(&p->sighand->siglock, flags);
- return ret;
-}
-
int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
{
@@ -1324,29 +1300,37 @@ static inline int task_cputime_expired(const struct task_cputime *sample,
* fastpath_timer_check - POSIX CPU timers fast path.
*
* @tsk: The task (thread) being checked.
- * @sig: The signal pointer for that task.
*
- * If there are no timers set return false. Otherwise snapshot the task and
- * thread group timers, then compare them with the corresponding expiration
- # times. Returns true if a timer has expired, else returns false.
+ * Check the task and thread group timers. If both are zero (there are no
+ * timers set) return false. Otherwise snapshot the task and thread group
+ * timers and compare them with the corresponding expiration times. Return
+ * true if a timer has expired, else return false.
*/
-static inline int fastpath_timer_check(struct task_struct *tsk,
- struct signal_struct *sig)
+static inline int fastpath_timer_check(struct task_struct *tsk)
{
- struct task_cputime task_sample = {
- .utime = tsk->utime,
- .stime = tsk->stime,
- .sum_exec_runtime = tsk->se.sum_exec_runtime
- };
- struct task_cputime group_sample;
+ struct signal_struct *sig = tsk->signal;
- if (task_cputime_zero(&tsk->cputime_expires) &&
- task_cputime_zero(&sig->cputime_expires))
+ if (unlikely(!sig))
return 0;
- if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
- return 1;
- thread_group_cputime(tsk, &group_sample);
- return task_cputime_expired(&group_sample, &sig->cputime_expires);
+
+ if (!task_cputime_zero(&tsk->cputime_expires)) {
+ struct task_cputime task_sample = {
+ .utime = tsk->utime,
+ .stime = tsk->stime,
+ .sum_exec_runtime = tsk->se.sum_exec_runtime
+ };
+
+ if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
+ return 1;
+ }
+ if (!task_cputime_zero(&sig->cputime_expires)) {
+ struct task_cputime group_sample;
+
+ thread_group_cputime(tsk, &group_sample);
+ if (task_cputime_expired(&group_sample, &sig->cputime_expires))
+ return 1;
+ }
+ return 0;
}
/*
@@ -1358,43 +1342,34 @@ void run_posix_cpu_timers(struct task_struct *tsk)
{
LIST_HEAD(firing);
struct k_itimer *timer, *next;
- struct signal_struct *sig;
- struct sighand_struct *sighand;
- unsigned long flags;
BUG_ON(!irqs_disabled());
- /* Pick up tsk->signal and make sure it's valid. */
- sig = tsk->signal;
/*
* The fast path checks that there are no expired thread or thread
- * group timers. If that's so, just return. Also check that
- * tsk->signal is non-NULL; this probably can't happen but cover the
- * possibility anyway.
+ * group timers. If that's so, just return.
*/
- if (unlikely(!sig) || !fastpath_timer_check(tsk, sig))
+ if (!fastpath_timer_check(tsk))
return;
- sighand = lock_task_sighand(tsk, &flags);
- if (likely(sighand)) {
- /*
- * Here we take off tsk->signal->cpu_timers[N] and
- * tsk->cpu_timers[N] all the timers that are firing, and
- * put them on the firing list.
- */
- check_thread_timers(tsk, &firing);
- check_process_timers(tsk, &firing);
+ spin_lock(&tsk->sighand->siglock);
+ /*
+ * Here we take off tsk->signal->cpu_timers[N] and
+ * tsk->cpu_timers[N] all the timers that are firing, and
+ * put them on the firing list.
+ */
+ check_thread_timers(tsk, &firing);
+ check_process_timers(tsk, &firing);
- /*
- * We must release these locks before taking any timer's lock.
- * There is a potential race with timer deletion here, as the
- * siglock now protects our private firing list. We have set
- * the firing flag in each timer, so that a deletion attempt
- * that gets the timer lock before we do will give it up and
- * spin until we've taken care of that timer below.
- */
- }
- unlock_task_sighand(tsk, &flags);
+ /*
+ * We must release these locks before taking any timer's lock.
+ * There is a potential race with timer deletion here, as the
+ * siglock now protects our private firing list. We have set
+ * the firing flag in each timer, so that a deletion attempt
+ * that gets the timer lock before we do will give it up and
+ * spin until we've taken care of that timer below.
+ */
+ spin_unlock(&tsk->sighand->siglock);
/*
* Now that all the timers on our list have the firing flag,
@@ -1433,7 +1408,7 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
struct list_head *head;
BUG_ON(clock_idx == CPUCLOCK_SCHED);
- cpu_clock_sample_group_locked(clock_idx, tsk, &now);
+ cpu_clock_sample_group(clock_idx, tsk, &now);
if (oldval) {
if (!cputime_eq(*oldval, cputime_zero)) {