diff options
Diffstat (limited to 'kernel/posix-cpu-timers.c')
| -rw-r--r-- | kernel/posix-cpu-timers.c | 76 |
1 files changed, 44 insertions, 32 deletions
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c index 9641958..d9dc5ed 100644 --- a/kernel/posix-cpu-timers.c +++ b/kernel/posix-cpu-timers.c @@ -233,7 +233,8 @@ void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times) /* * 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 task sighand lock held for safe while_each_thread() + * traversal. */ static int cpu_clock_sample_group(const clockid_t which_clock, struct task_struct *p, @@ -455,8 +456,7 @@ static inline int expires_gt(cputime_t expires, cputime_t new_exp) /* * Insert the timer on the appropriate list before any timers that - * expire later. This must be called with the tasklist_lock held - * for reading, interrupts disabled and p->sighand->siglock taken. + * expire later. This must be called with the sighand lock held. */ static void arm_timer(struct k_itimer *timer) { @@ -547,7 +547,8 @@ static void cpu_timer_fire(struct k_itimer *timer) /* * Sample a process (thread group) timer for the given group_leader task. - * Must be called with tasklist_lock held for reading. + * Must be called with task sighand lock held for safe while_each_thread() + * traversal. */ static int cpu_timer_sample_group(const clockid_t which_clock, struct task_struct *p, @@ -610,9 +611,11 @@ static inline void posix_cpu_timer_kick_nohz(void) { } * If we return TIMER_RETRY, it's necessary to release the timer's lock * and try again. (This happens when the timer is in the middle of firing.) */ -static int posix_cpu_timer_set(struct k_itimer *timer, int flags, +static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags, struct itimerspec *new, struct itimerspec *old) { + unsigned long flags; + struct sighand_struct *sighand; struct task_struct *p = timer->it.cpu.task; unsigned long long old_expires, new_expires, old_incr, val; int ret; @@ -621,14 +624,16 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int flags, new_expires = timespec_to_sample(timer->it_clock, &new->it_value); - read_lock(&tasklist_lock); /* - * We need the tasklist_lock to protect against reaping that - * clears p->sighand. If p has just been reaped, we can no + * Protect against sighand release/switch in exit/exec and p->cpu_timers + * and p->signal->cpu_timers read/write in arm_timer() + */ + sighand = lock_task_sighand(p, &flags); + /* + * If p has just been reaped, we can no * longer get any information about it at all. */ - if (unlikely(p->sighand == NULL)) { - read_unlock(&tasklist_lock); + if (unlikely(sighand == NULL)) { return -ESRCH; } @@ -639,7 +644,6 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int flags, ret = 0; old_incr = timer->it.cpu.incr; - spin_lock(&p->sighand->siglock); old_expires = timer->it.cpu.expires; if (unlikely(timer->it.cpu.firing)) { timer->it.cpu.firing = -1; @@ -696,12 +700,11 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int flags, * disable this firing since we are already reporting * it as an overrun (thanks to bump_cpu_timer above). */ - spin_unlock(&p->sighand->siglock); - read_unlock(&tasklist_lock); + unlock_task_sighand(p, &flags); goto out; } - if (new_expires != 0 && !(flags & TIMER_ABSTIME)) { + if (new_expires != 0 && !(timer_flags & TIMER_ABSTIME)) { new_expires += val; } @@ -715,9 +718,7 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int flags, arm_timer(timer); } - spin_unlock(&p->sighand->siglock); - read_unlock(&tasklist_lock); - + unlock_task_sighand(p, &flags); /* * Install the new reload setting, and * set up the signal and overrun bookkeeping. @@ -779,8 +780,16 @@ static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp) if (CPUCLOCK_PERTHREAD(timer->it_clock)) { cpu_clock_sample(timer->it_clock, p, &now); } else { - read_lock(&tasklist_lock); - if (unlikely(p->sighand == NULL)) { + struct sighand_struct *sighand; + unsigned long flags; + + /* + * Protect against sighand release/switch in exit/exec and + * also make timer sampling safe if it ends up calling + * thread_group_cputime(). + */ + sighand = lock_task_sighand(p, &flags); + if (unlikely(sighand == NULL)) { /* * The process has been reaped. * We can't even collect a sample any more. @@ -789,11 +798,10 @@ static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp) timer->it.cpu.expires = 0; sample_to_timespec(timer->it_clock, timer->it.cpu.expires, &itp->it_value); - read_unlock(&tasklist_lock); } else { cpu_timer_sample_group(timer->it_clock, p, &now); + unlock_task_sighand(p, &flags); } - read_unlock(&tasklist_lock); } if (now < timer->it.cpu.expires) { @@ -1007,6 +1015,8 @@ static void check_process_timers(struct task_struct *tsk, */ void posix_cpu_timer_schedule(struct k_itimer *timer) { + struct sighand_struct *sighand; + unsigned long flags; struct task_struct *p = timer->it.cpu.task; unsigned long long now; @@ -1021,27 +1031,31 @@ void posix_cpu_timer_schedule(struct k_itimer *timer) if (unlikely(p->exit_state)) goto out; - read_lock(&tasklist_lock); /* arm_timer needs it. */ - spin_lock(&p->sighand->siglock); + /* Protect timer list r/w in arm_timer() */ + sighand = lock_task_sighand(p, &flags); + if (!sighand) + goto out; } else { - read_lock(&tasklist_lock); - if (unlikely(p->sighand == NULL)) { + /* + * Protect arm_timer() and timer sampling in case of call to + * thread_group_cputime(). + */ + sighand = lock_task_sighand(p, &flags); + if (unlikely(sighand == NULL)) { /* * The process has been reaped. * We can't even collect a sample any more. */ timer->it.cpu.expires = 0; - read_unlock(&tasklist_lock); goto out; } else if (unlikely(p->exit_state) && thread_group_empty(p)) { - read_unlock(&tasklist_lock); + unlock_task_sighand(p, &flags); /* Optimizations: if the process is dying, no need to rearm */ goto out; } - spin_lock(&p->sighand->siglock); cpu_timer_sample_group(timer->it_clock, p, &now); bump_cpu_timer(timer, now); - /* Leave the tasklist_lock locked for the call below. */ + /* Leave the sighand locked for the call below. */ } /* @@ -1049,12 +1063,10 @@ void posix_cpu_timer_schedule(struct k_itimer *timer) */ BUG_ON(!irqs_disabled()); arm_timer(timer); - spin_unlock(&p->sighand->siglock); - read_unlock(&tasklist_lock); + unlock_task_sighand(p, &flags); /* Kick full dynticks CPUs in case they need to tick on the new timer */ posix_cpu_timer_kick_nohz(); - out: timer->it_overrun_last = timer->it_overrun; timer->it_overrun = -1; |
