From 8e8be45e8e55daa381028aec339829929ddb53a5 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 2 Sep 2010 16:16:14 -0700 Subject: rcu: add priority-inversion testing to rcutorture Add an optional test to force long-term preemption of RCU read-side critical sections, controlled by new test_boost, test_boost_interval, and test_boost_duration module parameters. This is to be used to test RCU priority boosting. Signed-off-by: Paul E. McKenney --- kernel/rcutorture.c | 270 +++++++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 259 insertions(+), 11 deletions(-) diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c index 9d8e8fb2515f..89613f97ff26 100644 --- a/kernel/rcutorture.c +++ b/kernel/rcutorture.c @@ -47,6 +47,7 @@ #include #include #include +#include MODULE_LICENSE("GPL"); MODULE_AUTHOR("Paul E. McKenney and " @@ -64,6 +65,9 @@ static int irqreader = 1; /* RCU readers from irq (timers). */ static int fqs_duration = 0; /* Duration of bursts (us), 0 to disable. */ static int fqs_holdoff = 0; /* Hold time within burst (us). */ static int fqs_stutter = 3; /* Wait time between bursts (s). */ +static int test_boost = 1; /* Test RCU prio boost: 0=no, 1=maybe, 2=yes. */ +static int test_boost_interval = 7; /* Interval between boost tests, seconds. */ +static int test_boost_duration = 4; /* Duration of each boost test, seconds. */ static char *torture_type = "rcu"; /* What RCU implementation to torture. */ module_param(nreaders, int, 0444); @@ -88,6 +92,12 @@ module_param(fqs_holdoff, int, 0444); MODULE_PARM_DESC(fqs_holdoff, "Holdoff time within fqs bursts (us)"); module_param(fqs_stutter, int, 0444); MODULE_PARM_DESC(fqs_stutter, "Wait time between fqs bursts (s)"); +module_param(test_boost, int, 0444); +MODULE_PARM_DESC(test_boost, "Test RCU prio boost: 0=no, 1=maybe, 2=yes."); +module_param(test_boost_interval, int, 0444); +MODULE_PARM_DESC(test_boost_interval, "Interval between boost tests, seconds."); +module_param(test_boost_duration, int, 0444); +MODULE_PARM_DESC(test_boost_duration, "Duration of each boost test, seconds."); module_param(torture_type, charp, 0444); MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, rcu_bh, srcu)"); @@ -109,6 +119,7 @@ static struct task_struct *stats_task; static struct task_struct *shuffler_task; static struct task_struct *stutter_task; static struct task_struct *fqs_task; +static struct task_struct *boost_tasks[NR_CPUS]; #define RCU_TORTURE_PIPE_LEN 10 @@ -134,6 +145,12 @@ static atomic_t n_rcu_torture_alloc_fail; static atomic_t n_rcu_torture_free; static atomic_t n_rcu_torture_mberror; static atomic_t n_rcu_torture_error; +static long n_rcu_torture_boost_ktrerror; +static long n_rcu_torture_boost_rterror; +static long n_rcu_torture_boost_allocerror; +static long n_rcu_torture_boost_afferror; +static long n_rcu_torture_boost_failure; +static long n_rcu_torture_boosts; static long n_rcu_torture_timers; static struct list_head rcu_torture_removed; static cpumask_var_t shuffle_tmp_mask; @@ -147,6 +164,16 @@ static int stutter_pause_test; #endif int rcutorture_runnable = RCUTORTURE_RUNNABLE_INIT; +#ifdef CONFIG_RCU_BOOST +#define rcu_can_boost() 1 +#else /* #ifdef CONFIG_RCU_BOOST */ +#define rcu_can_boost() 0 +#endif /* #else #ifdef CONFIG_RCU_BOOST */ + +static unsigned long boost_starttime; /* jiffies of next boost test start. */ +DEFINE_MUTEX(boost_mutex); /* protect setting boost_starttime */ + /* and boost task create/destroy. */ + /* Mediate rmmod and system shutdown. Concurrent rmmod & shutdown illegal! */ #define FULLSTOP_DONTSTOP 0 /* Normal operation. */ @@ -277,6 +304,7 @@ struct rcu_torture_ops { void (*fqs)(void); int (*stats)(char *page); int irq_capable; + int can_boost; char *name; }; @@ -366,6 +394,7 @@ static struct rcu_torture_ops rcu_ops = { .fqs = rcu_force_quiescent_state, .stats = NULL, .irq_capable = 1, + .can_boost = rcu_can_boost(), .name = "rcu" }; @@ -408,6 +437,7 @@ static struct rcu_torture_ops rcu_sync_ops = { .fqs = rcu_force_quiescent_state, .stats = NULL, .irq_capable = 1, + .can_boost = rcu_can_boost(), .name = "rcu_sync" }; @@ -424,6 +454,7 @@ static struct rcu_torture_ops rcu_expedited_ops = { .fqs = rcu_force_quiescent_state, .stats = NULL, .irq_capable = 1, + .can_boost = rcu_can_boost(), .name = "rcu_expedited" }; @@ -683,6 +714,110 @@ static struct rcu_torture_ops sched_expedited_ops = { .name = "sched_expedited" }; +/* + * RCU torture priority-boost testing. Runs one real-time thread per + * CPU for moderate bursts, repeatedly registering RCU callbacks and + * spinning waiting for them to be invoked. If a given callback takes + * too long to be invoked, we assume that priority inversion has occurred. + */ + +struct rcu_boost_inflight { + struct rcu_head rcu; + int inflight; +}; + +static void rcu_torture_boost_cb(struct rcu_head *head) +{ + struct rcu_boost_inflight *rbip = + container_of(head, struct rcu_boost_inflight, rcu); + + smp_mb(); /* Ensure RCU-core accesses precede clearing ->inflight */ + rbip->inflight = 0; +} + +static int rcu_torture_boost(void *arg) +{ + unsigned long call_rcu_time; + unsigned long endtime; + unsigned long oldstarttime; + struct rcu_boost_inflight rbi = { .inflight = 0 }; + struct sched_param sp; + + VERBOSE_PRINTK_STRING("rcu_torture_boost started"); + + /* Set real-time priority. */ + sp.sched_priority = 1; + if (sched_setscheduler(current, SCHED_FIFO, &sp) < 0) { + VERBOSE_PRINTK_STRING("rcu_torture_boost RT prio failed!"); + n_rcu_torture_boost_rterror++; + } + + /* Each pass through the following loop does one boost-test cycle. */ + do { + /* Wait for the next test interval. */ + oldstarttime = boost_starttime; + while (jiffies - oldstarttime > ULONG_MAX / 2) { + schedule_timeout_uninterruptible(1); + rcu_stutter_wait("rcu_torture_boost"); + if (kthread_should_stop() || + fullstop != FULLSTOP_DONTSTOP) + goto checkwait; + } + + /* Do one boost-test interval. */ + endtime = oldstarttime + test_boost_duration * HZ; + call_rcu_time = jiffies; + while (jiffies - endtime > ULONG_MAX / 2) { + /* If we don't have a callback in flight, post one. */ + if (!rbi.inflight) { + smp_mb(); /* RCU core before ->inflight = 1. */ + rbi.inflight = 1; + call_rcu(&rbi.rcu, rcu_torture_boost_cb); + if (jiffies - call_rcu_time > + test_boost_duration * HZ - HZ / 2) { + VERBOSE_PRINTK_STRING("rcu_torture_boost boosting failed"); + n_rcu_torture_boost_failure++; + } + call_rcu_time = jiffies; + } + cond_resched(); + rcu_stutter_wait("rcu_torture_boost"); + if (kthread_should_stop() || + fullstop != FULLSTOP_DONTSTOP) + goto checkwait; + } + + /* + * Set the start time of the next test interval. + * Yes, this is vulnerable to long delays, but such + * delays simply cause a false negative for the next + * interval. Besides, we are running at RT priority, + * so delays should be relatively rare. + */ + while (oldstarttime == boost_starttime) { + if (mutex_trylock(&boost_mutex)) { + boost_starttime = jiffies + + test_boost_interval * HZ; + n_rcu_torture_boosts++; + mutex_unlock(&boost_mutex); + break; + } + schedule_timeout_uninterruptible(1); + } + + /* Go do the stutter. */ +checkwait: rcu_stutter_wait("rcu_torture_boost"); + } while (!kthread_should_stop() && fullstop == FULLSTOP_DONTSTOP); + + /* Clean up and exit. */ + VERBOSE_PRINTK_STRING("rcu_torture_boost task stopping"); + rcutorture_shutdown_absorb("rcu_torture_boost"); + while (!kthread_should_stop() || rbi.inflight) + schedule_timeout_uninterruptible(1); + smp_mb(); /* order accesses to ->inflight before stack-frame death. */ + return 0; +} + /* * RCU torture force-quiescent-state kthread. Repeatedly induces * bursts of calls to force_quiescent_state(), increasing the probability @@ -933,7 +1068,8 @@ rcu_torture_printk(char *page) cnt += sprintf(&page[cnt], "%s%s ", torture_type, TORTURE_FLAG); cnt += sprintf(&page[cnt], "rtc: %p ver: %ld tfle: %d rta: %d rtaf: %d rtf: %d " - "rtmbe: %d nt: %ld", + "rtmbe: %d rtbke: %ld rtbre: %ld rtbae: %ld rtbafe: %ld " + "rtbf: %ld rtb: %ld nt: %ld", rcu_torture_current, rcu_torture_current_version, list_empty(&rcu_torture_freelist), @@ -941,8 +1077,19 @@ rcu_torture_printk(char *page) atomic_read(&n_rcu_torture_alloc_fail), atomic_read(&n_rcu_torture_free), atomic_read(&n_rcu_torture_mberror), + n_rcu_torture_boost_ktrerror, + n_rcu_torture_boost_rterror, + n_rcu_torture_boost_allocerror, + n_rcu_torture_boost_afferror, + n_rcu_torture_boost_failure, + n_rcu_torture_boosts, n_rcu_torture_timers); - if (atomic_read(&n_rcu_torture_mberror) != 0) + if (atomic_read(&n_rcu_torture_mberror) != 0 || + n_rcu_torture_boost_ktrerror != 0 || + n_rcu_torture_boost_rterror != 0 || + n_rcu_torture_boost_allocerror != 0 || + n_rcu_torture_boost_afferror != 0 || + n_rcu_torture_boost_failure != 0) cnt += sprintf(&page[cnt], " !!!"); cnt += sprintf(&page[cnt], "\n%s%s ", torture_type, TORTURE_FLAG); if (i > 1) { @@ -1094,22 +1241,91 @@ rcu_torture_stutter(void *arg) } static inline void -rcu_torture_print_module_parms(char *tag) +rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, char *tag) { printk(KERN_ALERT "%s" TORTURE_FLAG "--- %s: nreaders=%d nfakewriters=%d " "stat_interval=%d verbose=%d test_no_idle_hz=%d " "shuffle_interval=%d stutter=%d irqreader=%d " - "fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d\n", + "fqs_duration=%d fqs_holdoff=%d fqs_stutter=%d " + "test_boost=%d/%d test_boost_interval=%d " + "test_boost_duration=%d\n", torture_type, tag, nrealreaders, nfakewriters, stat_interval, verbose, test_no_idle_hz, shuffle_interval, - stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter); + stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter, + test_boost, cur_ops->can_boost, + test_boost_interval, test_boost_duration); } -static struct notifier_block rcutorture_nb = { +static struct notifier_block rcutorture_shutdown_nb = { .notifier_call = rcutorture_shutdown_notify, }; +static void rcutorture_booster_cleanup(int cpu) +{ + struct task_struct *t; + + if (boost_tasks[cpu] == NULL) + return; + mutex_lock(&boost_mutex); + VERBOSE_PRINTK_STRING("Stopping rcu_torture_boost task"); + t = boost_tasks[cpu]; + boost_tasks[cpu] = NULL; + mutex_unlock(&boost_mutex); + + /* This must be outside of the mutex, otherwise deadlock! */ + kthread_stop(t); +} + +static int rcutorture_booster_init(int cpu) +{ + int retval; + + if (boost_tasks[cpu] != NULL) + return 0; /* Already created, nothing more to do. */ + + /* Don't allow time recalculation while creating a new task. */ + mutex_lock(&boost_mutex); + VERBOSE_PRINTK_STRING("Creating rcu_torture_boost task"); + boost_tasks[cpu] = kthread_create(rcu_torture_boost, NULL, + "rcu_torture_boost"); + if (IS_ERR(boost_tasks[cpu])) { + retval = PTR_ERR(boost_tasks[cpu]); + VERBOSE_PRINTK_STRING("rcu_torture_boost task create failed"); + n_rcu_torture_boost_ktrerror++; + boost_tasks[cpu] = NULL; + mutex_unlock(&boost_mutex); + return retval; + } + kthread_bind(boost_tasks[cpu], cpu); + wake_up_process(boost_tasks[cpu]); + mutex_unlock(&boost_mutex); + return 0; +} + +static int rcutorture_cpu_notify(struct notifier_block *self, + unsigned long action, void *hcpu) +{ + long cpu = (long)hcpu; + + switch (action) { + case CPU_ONLINE: + case CPU_DOWN_FAILED: + (void)rcutorture_booster_init(cpu); + break; + case CPU_DOWN_PREPARE: + rcutorture_booster_cleanup(cpu); + break; + default: + break; + } + return NOTIFY_OK; +} + +static struct notifier_block rcutorture_cpu_nb = { + .notifier_call = rcutorture_cpu_notify, +}; + static void rcu_torture_cleanup(void) { @@ -1127,7 +1343,7 @@ rcu_torture_cleanup(void) } fullstop = FULLSTOP_RMMOD; mutex_unlock(&fullstop_mutex); - unregister_reboot_notifier(&rcutorture_nb); + unregister_reboot_notifier(&rcutorture_shutdown_nb); if (stutter_task) { VERBOSE_PRINTK_STRING("Stopping rcu_torture_stutter task"); kthread_stop(stutter_task); @@ -1184,6 +1400,12 @@ rcu_torture_cleanup(void) kthread_stop(fqs_task); } fqs_task = NULL; + if ((test_boost == 1 && cur_ops->can_boost) || + test_boost == 2) { + unregister_cpu_notifier(&rcutorture_cpu_nb); + for_each_possible_cpu(i) + rcutorture_booster_cleanup(i); + } /* Wait for all RCU callbacks to fire. */ @@ -1195,9 +1417,9 @@ rcu_torture_cleanup(void) if (cur_ops->cleanup) cur_ops->cleanup(); if (atomic_read(&n_rcu_torture_error)) - rcu_torture_print_module_parms("End of test: FAILURE"); + rcu_torture_print_module_parms(cur_ops, "End of test: FAILURE"); else - rcu_torture_print_module_parms("End of test: SUCCESS"); + rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS"); } static int __init @@ -1242,7 +1464,7 @@ rcu_torture_init(void) nrealreaders = nreaders; else nrealreaders = 2 * num_online_cpus(); - rcu_torture_print_module_parms("Start of test"); + rcu_torture_print_module_parms(cur_ops, "Start of test"); fullstop = FULLSTOP_DONTSTOP; /* Set up the freelist. */ @@ -1263,6 +1485,12 @@ rcu_torture_init(void) atomic_set(&n_rcu_torture_free, 0); atomic_set(&n_rcu_torture_mberror, 0); atomic_set(&n_rcu_torture_error, 0); + n_rcu_torture_boost_ktrerror = 0; + n_rcu_torture_boost_rterror = 0; + n_rcu_torture_boost_allocerror = 0; + n_rcu_torture_boost_afferror = 0; + n_rcu_torture_boost_failure = 0; + n_rcu_torture_boosts = 0; for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) atomic_set(&rcu_torture_wcount[i], 0); for_each_possible_cpu(cpu) { @@ -1376,7 +1604,27 @@ rcu_torture_init(void) goto unwind; } } - register_reboot_notifier(&rcutorture_nb); + if (test_boost_interval < 1) + test_boost_interval = 1; + if (test_boost_duration < 2) + test_boost_duration = 2; + if ((test_boost == 1 && cur_ops->can_boost) || + test_boost == 2) { + int retval; + + boost_starttime = jiffies + test_boost_interval * HZ; + register_cpu_notifier(&rcutorture_cpu_nb); + for_each_possible_cpu(i) { + if (cpu_is_offline(i)) + continue; /* Heuristic: CPU can go offline. */ + retval = rcutorture_booster_init(i); + if (retval < 0) { + firsterr = retval; + goto unwind; + } + } + } + register_reboot_notifier(&rcutorture_shutdown_nb); mutex_unlock(&fullstop_mutex); return 0; -- cgit v1.2.2