From 78f2c7db6068fd6ef75b8c120f04a388848eacb5 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 25 Jan 2008 21:08:27 +0100 Subject: [PATCH] sched: SCHED_FIFO/SCHED_RR watchdog timer Introduce a new rlimit that allows the user to set a runtime timeout on real-time tasks their slice. Once this limit is exceeded the task will receive SIGXCPU. So it measures runtime since the last sleep. Input and ideas by Thomas Gleixner and Lennart Poettering. Signed-off-by: Peter Zijlstra CC: Lennart Poettering CC: Michael Kerrisk CC: Ulrich Drepper Signed-off-by: Ingo Molnar --- include/asm-generic/resource.h | 5 +++-- include/linux/sched.h | 1 + kernel/posix-cpu-timers.c | 29 +++++++++++++++++++++++++++++ kernel/sched_rt.c | 30 ++++++++++++++++++++++++++++++ 4 files changed, 63 insertions(+), 2 deletions(-) diff --git a/include/asm-generic/resource.h b/include/asm-generic/resource.h index a4a22cc35898..587566f95f6c 100644 --- a/include/asm-generic/resource.h +++ b/include/asm-generic/resource.h @@ -44,8 +44,8 @@ #define RLIMIT_NICE 13 /* max nice prio allowed to raise to 0-39 for nice level 19 .. -20 */ #define RLIMIT_RTPRIO 14 /* maximum realtime priority */ - -#define RLIM_NLIMITS 15 +#define RLIMIT_RTTIME 15 /* timeout for RT tasks in us */ +#define RLIM_NLIMITS 16 /* * SuS says limits have to be unsigned. @@ -86,6 +86,7 @@ [RLIMIT_MSGQUEUE] = { MQ_BYTES_MAX, MQ_BYTES_MAX }, \ [RLIMIT_NICE] = { 0, 0 }, \ [RLIMIT_RTPRIO] = { 0, 0 }, \ + [RLIMIT_RTTIME] = { RLIM_INFINITY, RLIM_INFINITY }, \ } #endif /* __KERNEL__ */ diff --git a/include/linux/sched.h b/include/linux/sched.h index a06d09ebd5c6..fe3f8fbc614e 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -932,6 +932,7 @@ struct sched_entity { struct sched_rt_entity { struct list_head run_list; unsigned int time_slice; + unsigned long timeout; }; struct task_struct { diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c index 68c96376e84a..2c076b36c4f6 100644 --- a/kernel/posix-cpu-timers.c +++ b/kernel/posix-cpu-timers.c @@ -967,6 +967,7 @@ static void check_thread_timers(struct task_struct *tsk, { int maxfire; struct list_head *timers = tsk->cpu_timers; + struct signal_struct *const sig = tsk->signal; maxfire = 20; tsk->it_prof_expires = cputime_zero; @@ -1011,6 +1012,34 @@ static void check_thread_timers(struct task_struct *tsk, t->firing = 1; list_move_tail(&t->entry, firing); } + + /* + * Check for the special case thread timers. + */ + if (sig->rlim[RLIMIT_RTTIME].rlim_cur != RLIM_INFINITY) { + unsigned long hard = sig->rlim[RLIMIT_RTTIME].rlim_max; + unsigned long *soft = &sig->rlim[RLIMIT_RTTIME].rlim_cur; + + if (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. + */ + __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk); + return; + } + if (tsk->rt.timeout > DIV_ROUND_UP(*soft, USEC_PER_SEC/HZ)) { + /* + * At the soft limit, send a SIGXCPU every second. + */ + if (sig->rlim[RLIMIT_RTTIME].rlim_cur + < sig->rlim[RLIMIT_RTTIME].rlim_max) { + sig->rlim[RLIMIT_RTTIME].rlim_cur += + USEC_PER_SEC; + } + __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk); + } + } } /* diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c index 29963af782ae..f350f7b15158 100644 --- a/kernel/sched_rt.c +++ b/kernel/sched_rt.c @@ -116,6 +116,9 @@ static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup) inc_cpu_load(rq, p->se.load.weight); inc_rt_tasks(p, rq); + + if (wakeup) + p->rt.timeout = 0; } /* @@ -834,11 +837,38 @@ static void prio_changed_rt(struct rq *rq, struct task_struct *p, } } +static void watchdog(struct rq *rq, struct task_struct *p) +{ + unsigned long soft, hard; + + if (!p->signal) + return; + + soft = p->signal->rlim[RLIMIT_RTTIME].rlim_cur; + hard = p->signal->rlim[RLIMIT_RTTIME].rlim_max; + + if (soft != RLIM_INFINITY) { + unsigned long next; + + p->rt.timeout++; + next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ); + if (next > p->rt.timeout) { + u64 next_time = p->se.sum_exec_runtime; + + next_time += next * (NSEC_PER_SEC/HZ); + if (p->it_sched_expires > next_time) + p->it_sched_expires = next_time; + } else + p->it_sched_expires = p->se.sum_exec_runtime; + } +} static void task_tick_rt(struct rq *rq, struct task_struct *p) { update_curr_rt(rq); + watchdog(rq, p); + /* * RR tasks need a special form of timeslice management. * FIFO tasks have no timeslices. -- 2.20.1