X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=kernel%2Fposix-cpu-timers.c;h=657f77697415b2879c07b85e759e8d19b0880b93;hb=276e26c3160602efea1d0acc9fe7b45bb4c2c8e1;hp=5667fef89dd1fa98ca1180fe42e2e659d9505069;hpb=1711ef3866b0360e102327389fe4b76c849bbe83;p=linux-2.6 diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c index 5667fef89d..657f776974 100644 --- a/kernel/posix-cpu-timers.c +++ b/kernel/posix-cpu-timers.c @@ -87,6 +87,19 @@ static inline union cpu_time_count cpu_time_sub(const clockid_t which_clock, return a; } +/* + * Divide and limit the result to res >= 1 + * + * This is necessary to prevent signal delivery starvation, when the result of + * the division would be rounded down to 0. + */ +static inline cputime_t cputime_div_non_zero(cputime_t time, unsigned long div) +{ + cputime_t res = cputime_div(time, div); + + return max_t(cputime_t, res, 1); +} + /* * Update expiry time from increment, and increase overrun count, * given the current clock sample. @@ -291,7 +304,7 @@ int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp) * should be able to see it. */ struct task_struct *p; - read_lock(&tasklist_lock); + rcu_read_lock(); p = find_task_by_pid(pid); if (p) { if (CPUCLOCK_PERTHREAD(which_clock)) { @@ -299,12 +312,17 @@ int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp) error = cpu_clock_sample(which_clock, p, &rtn); } - } else if (p->tgid == pid && p->signal) { - error = cpu_clock_sample_group(which_clock, - p, &rtn); + } else { + read_lock(&tasklist_lock); + if (p->tgid == pid && p->signal) { + error = + cpu_clock_sample_group(which_clock, + p, &rtn); + } + read_unlock(&tasklist_lock); } } - read_unlock(&tasklist_lock); + rcu_read_unlock(); } if (error) @@ -483,8 +501,8 @@ static void process_timer_rebalance(struct task_struct *p, BUG(); break; case CPUCLOCK_PROF: - left = cputime_div(cputime_sub(expires.cpu, val.cpu), - nthreads); + left = cputime_div_non_zero(cputime_sub(expires.cpu, val.cpu), + nthreads); do { if (likely(!(t->flags & PF_EXITING))) { ticks = cputime_add(prof_ticks(t), left); @@ -498,8 +516,8 @@ static void process_timer_rebalance(struct task_struct *p, } while (t != p); break; case CPUCLOCK_VIRT: - left = cputime_div(cputime_sub(expires.cpu, val.cpu), - nthreads); + left = cputime_div_non_zero(cputime_sub(expires.cpu, val.cpu), + nthreads); do { if (likely(!(t->flags & PF_EXITING))) { ticks = cputime_add(virt_ticks(t), left); @@ -515,6 +533,7 @@ static void process_timer_rebalance(struct task_struct *p, case CPUCLOCK_SCHED: nsleft = expires.sched - val.sched; do_div(nsleft, nthreads); + nsleft = max_t(unsigned long long, nsleft, 1); do { if (likely(!(t->flags & PF_EXITING))) { ns = t->sched_time + nsleft; @@ -1159,12 +1178,13 @@ static void check_process_timers(struct task_struct *tsk, prof_left = cputime_sub(prof_expires, utime); prof_left = cputime_sub(prof_left, stime); - prof_left = cputime_div(prof_left, nthreads); + prof_left = cputime_div_non_zero(prof_left, nthreads); virt_left = cputime_sub(virt_expires, utime); - virt_left = cputime_div(virt_left, nthreads); + virt_left = cputime_div_non_zero(virt_left, nthreads); if (sched_expires) { sched_left = sched_expires - sched_time; do_div(sched_left, nthreads); + sched_left = max_t(unsigned long long, sched_left, 1); } else { sched_left = 0; } @@ -1393,22 +1413,12 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx, } } -int posix_cpu_nsleep(const clockid_t which_clock, int flags, - struct timespec *rqtp, struct timespec __user *rmtp) +static int do_cpu_nanosleep(const clockid_t which_clock, int flags, + struct timespec *rqtp, struct itimerspec *it) { - struct restart_block *restart_block = - ¤t_thread_info()->restart_block; struct k_itimer timer; int error; - /* - * Diagnose required errors first. - */ - if (CPUCLOCK_PERTHREAD(which_clock) && - (CPUCLOCK_PID(which_clock) == 0 || - CPUCLOCK_PID(which_clock) == current->pid)) - return -EINVAL; - /* * Set up a temporary timer and then wait for it to go off. */ @@ -1420,11 +1430,12 @@ int posix_cpu_nsleep(const clockid_t which_clock, int flags, timer.it_process = current; if (!error) { static struct itimerspec zero_it; - struct itimerspec it = { .it_value = *rqtp, - .it_interval = {} }; + + memset(it, 0, sizeof *it); + it->it_value = *rqtp; spin_lock_irq(&timer.it_lock); - error = posix_cpu_timer_set(&timer, flags, &it, NULL); + error = posix_cpu_timer_set(&timer, flags, it, NULL); if (error) { spin_unlock_irq(&timer.it_lock); return error; @@ -1452,33 +1463,56 @@ int posix_cpu_nsleep(const clockid_t which_clock, int flags, * We were interrupted by a signal. */ sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp); - posix_cpu_timer_set(&timer, 0, &zero_it, &it); + posix_cpu_timer_set(&timer, 0, &zero_it, it); spin_unlock_irq(&timer.it_lock); - if ((it.it_value.tv_sec | it.it_value.tv_nsec) == 0) { + if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) { /* * It actually did fire already. */ return 0; } + error = -ERESTART_RESTARTBLOCK; + } + + return error; +} + +int posix_cpu_nsleep(const clockid_t which_clock, int flags, + struct timespec *rqtp, struct timespec __user *rmtp) +{ + struct restart_block *restart_block = + ¤t_thread_info()->restart_block; + struct itimerspec it; + int error; + + /* + * Diagnose required errors first. + */ + if (CPUCLOCK_PERTHREAD(which_clock) && + (CPUCLOCK_PID(which_clock) == 0 || + CPUCLOCK_PID(which_clock) == current->pid)) + return -EINVAL; + + error = do_cpu_nanosleep(which_clock, flags, rqtp, &it); + + if (error == -ERESTART_RESTARTBLOCK) { + + if (flags & TIMER_ABSTIME) + return -ERESTARTNOHAND; /* - * Report back to the user the time still remaining. - */ - if (rmtp != NULL && !(flags & TIMER_ABSTIME) && - copy_to_user(rmtp, &it.it_value, sizeof *rmtp)) + * Report back to the user the time still remaining. + */ + if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp)) return -EFAULT; restart_block->fn = posix_cpu_nsleep_restart; - /* Caller already set restart_block->arg1 */ restart_block->arg0 = which_clock; restart_block->arg1 = (unsigned long) rmtp; restart_block->arg2 = rqtp->tv_sec; restart_block->arg3 = rqtp->tv_nsec; - - error = -ERESTART_RESTARTBLOCK; } - return error; } @@ -1487,13 +1521,31 @@ long posix_cpu_nsleep_restart(struct restart_block *restart_block) clockid_t which_clock = restart_block->arg0; struct timespec __user *rmtp; struct timespec t; + struct itimerspec it; + int error; rmtp = (struct timespec __user *) restart_block->arg1; t.tv_sec = restart_block->arg2; t.tv_nsec = restart_block->arg3; restart_block->fn = do_no_restart_syscall; - return posix_cpu_nsleep(which_clock, TIMER_ABSTIME, &t, rmtp); + error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it); + + if (error == -ERESTART_RESTARTBLOCK) { + /* + * Report back to the user the time still remaining. + */ + if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp)) + return -EFAULT; + + restart_block->fn = posix_cpu_nsleep_restart; + restart_block->arg0 = which_clock; + restart_block->arg1 = (unsigned long) rmtp; + restart_block->arg2 = t.tv_sec; + restart_block->arg3 = t.tv_nsec; + } + return error; + }