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timers: fix itimer/many thread hang, v2

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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>
This commit is contained in:
Frank Mayhar 2008-09-12 09:54:39 -07:00 • committed by Ingo Molnar
parent 5ce73a4a5a
commit bb34d92f64
6 changed files with 226 additions and 323 deletions
Download patch file Download diff file Expand all files Collapse all files

177
kernel/posix-cpu-timers.c
View file

@ -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.
*/
@ -300,35 +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);
break;
}
return 0;
}
/*
* 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)
{
struct task_cputime cputime;
thread_group_cputime(p, &cputime);
switch (clock_idx) {
default:
return -EINVAL;
case CPUCLOCK_PROF:
cpu->cpu = cputime_add(cputime.utime, cputime.stime);
break;
case CPUCLOCK_VIRT:
cpu->cpu = cputime.utime;
break;
case CPUCLOCK_SCHED:
cpu->sched = thread_group_sched_runtime(p);
cpu->sched = p->se.sum_exec_runtime + task_delta_exec(p);
break;
}
return 0;
@ -342,13 +308,23 @@ 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;
struct task_cputime cputime;
thread_group_cputime(p, &cputime);
switch (which_clock) {
default:
return -EINVAL;
case CPUCLOCK_PROF:
cpu->cpu = cputime_add(cputime.utime, cputime.stime);
break;
case CPUCLOCK_VIRT:
cpu->cpu = cputime.utime;
break;
case CPUCLOCK_SCHED:
cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
break;
}
return 0;
}
@ -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)) {