From ad0dc7f94dbf417b1c7d42e1f0b250f045b27f8f Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 19 Feb 2014 10:51:42 -0800 Subject: [PATCH 1/1] rcutorture: Add forward-progress checking for writer The rcutorture output currently does not distinguish between stalls in the RCU implementation and stalls in the rcu_torture_writer() kthreads. This commit therefore adds some diagnostics to help distinguish between these two conditions, at least for the non-SRCU implementations. (SRCU does not provide evidence of update-side forward progress by design.) Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 19 +++++++++++++++++++ kernel/rcu/rcutorture.c | 37 +++++++++++++++++++++++++++++++++++++ kernel/rcu/tree.c | 33 +++++++++++++++++++++++++++++++++ 3 files changed, 89 insertions(+) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 00a7fd61b3c6..82973738125b 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -51,7 +51,17 @@ extern int rcu_expedited; /* for sysctl */ extern int rcutorture_runnable; /* for sysctl */ #endif /* #ifdef CONFIG_RCU_TORTURE_TEST */ +enum rcutorture_type { + RCU_FLAVOR, + RCU_BH_FLAVOR, + RCU_SCHED_FLAVOR, + SRCU_FLAVOR, + INVALID_RCU_FLAVOR +}; + #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) +void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, + unsigned long *gpnum, unsigned long *completed); void rcutorture_record_test_transition(void); void rcutorture_record_progress(unsigned long vernum); void do_trace_rcu_torture_read(const char *rcutorturename, @@ -60,6 +70,15 @@ void do_trace_rcu_torture_read(const char *rcutorturename, unsigned long c_old, unsigned long c); #else +static inline void rcutorture_get_gp_data(enum rcutorture_type test_type, + int *flags, + unsigned long *gpnum, + unsigned long *completed) +{ + *flags = 0; + *gpnum = 0; + *completed = 0; +} static inline void rcutorture_record_test_transition(void) { } diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index bd30bc61bc05..0d739e3797e3 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -138,6 +138,15 @@ static long n_barrier_attempts; static long n_barrier_successes; static struct list_head rcu_torture_removed; +static int rcu_torture_writer_state; +#define RTWS_FIXED_DELAY 0 +#define RTWS_DELAY 1 +#define RTWS_REPLACE 2 +#define RTWS_DEF_FREE 3 +#define RTWS_EXP_SYNC 4 +#define RTWS_STUTTER 5 +#define RTWS_STOPPING 6 + #if defined(MODULE) || defined(CONFIG_RCU_TORTURE_TEST_RUNNABLE) #define RCUTORTURE_RUNNABLE_INIT 1 #else @@ -214,6 +223,7 @@ rcu_torture_free(struct rcu_torture *p) */ struct rcu_torture_ops { + int ttype; void (*init)(void); int (*readlock)(void); void (*read_delay)(struct torture_random_state *rrsp); @@ -312,6 +322,7 @@ static void rcu_sync_torture_init(void) } static struct rcu_torture_ops rcu_ops = { + .ttype = RCU_FLAVOR, .init = rcu_sync_torture_init, .readlock = rcu_torture_read_lock, .read_delay = rcu_read_delay, @@ -355,6 +366,7 @@ static void rcu_bh_torture_deferred_free(struct rcu_torture *p) } static struct rcu_torture_ops rcu_bh_ops = { + .ttype = RCU_BH_FLAVOR, .init = rcu_sync_torture_init, .readlock = rcu_bh_torture_read_lock, .read_delay = rcu_read_delay, /* just reuse rcu's version. */ @@ -397,6 +409,7 @@ call_rcu_busted(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) } static struct rcu_torture_ops rcu_busted_ops = { + .ttype = INVALID_RCU_FLAVOR, .init = rcu_sync_torture_init, .readlock = rcu_torture_read_lock, .read_delay = rcu_read_delay, /* just reuse rcu's version. */ @@ -492,6 +505,7 @@ static void srcu_torture_synchronize_expedited(void) } static struct rcu_torture_ops srcu_ops = { + .ttype = SRCU_FLAVOR, .init = rcu_sync_torture_init, .readlock = srcu_torture_read_lock, .read_delay = srcu_read_delay, @@ -527,6 +541,7 @@ static void rcu_sched_torture_deferred_free(struct rcu_torture *p) } static struct rcu_torture_ops sched_ops = { + .ttype = RCU_SCHED_FLAVOR, .init = rcu_sync_torture_init, .readlock = sched_torture_read_lock, .read_delay = rcu_read_delay, /* just reuse rcu's version. */ @@ -699,12 +714,15 @@ rcu_torture_writer(void *arg) set_user_nice(current, MAX_NICE); do { + rcu_torture_writer_state = RTWS_FIXED_DELAY; schedule_timeout_uninterruptible(1); rp = rcu_torture_alloc(); if (rp == NULL) continue; rp->rtort_pipe_count = 0; + rcu_torture_writer_state = RTWS_DELAY; udelay(torture_random(&rand) & 0x3ff); + rcu_torture_writer_state = RTWS_REPLACE; old_rp = rcu_dereference_check(rcu_torture_current, current == writer_task); rp->rtort_mbtest = 1; @@ -721,8 +739,10 @@ rcu_torture_writer(void *arg) else exp = gp_exp; if (!exp) { + rcu_torture_writer_state = RTWS_DEF_FREE; cur_ops->deferred_free(old_rp); } else { + rcu_torture_writer_state = RTWS_EXP_SYNC; cur_ops->exp_sync(); list_add(&old_rp->rtort_free, &rcu_torture_removed); @@ -743,8 +763,10 @@ rcu_torture_writer(void *arg) } } rcutorture_record_progress(++rcu_torture_current_version); + rcu_torture_writer_state = RTWS_STUTTER; stutter_wait("rcu_torture_writer"); } while (!torture_must_stop()); + rcu_torture_writer_state = RTWS_STOPPING; torture_kthread_stopping("rcu_torture_writer"); return 0; } @@ -937,6 +959,7 @@ rcu_torture_printk(char *page) int i; long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 }; long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 }; + static unsigned long rtcv_snap = ULONG_MAX; for_each_possible_cpu(cpu) { for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) { @@ -997,6 +1020,20 @@ rcu_torture_printk(char *page) page += sprintf(page, "\n"); if (cur_ops->stats) cur_ops->stats(page); + if (rtcv_snap == rcu_torture_current_version && + rcu_torture_current != NULL) { + int __maybe_unused flags; + unsigned long __maybe_unused gpnum; + unsigned long __maybe_unused completed; + + rcutorture_get_gp_data(cur_ops->ttype, + &flags, &gpnum, &completed); + page += sprintf(page, + "??? Writer stall state %d g%lu c%lu f%#x\n", + rcu_torture_writer_state, + gpnum, completed, flags); + } + rtcv_snap = rcu_torture_current_version; } /* diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 0c47e300210a..3d15b5a82ae8 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -293,6 +293,39 @@ void rcutorture_record_test_transition(void) } EXPORT_SYMBOL_GPL(rcutorture_record_test_transition); +/* + * Send along grace-period-related data for rcutorture diagnostics. + */ +void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, + unsigned long *gpnum, unsigned long *completed) +{ + struct rcu_state *rsp = NULL; + + switch (test_type) { + case RCU_FLAVOR: + rsp = rcu_state; + break; + case RCU_BH_FLAVOR: + rsp = &rcu_bh_state; + break; + case RCU_SCHED_FLAVOR: + rsp = &rcu_sched_state; + break; + default: + break; + } + if (rsp != NULL) { + *flags = ACCESS_ONCE(rsp->gp_flags); + *gpnum = ACCESS_ONCE(rsp->gpnum); + *completed = ACCESS_ONCE(rsp->completed); + return; + } + *flags = 0; + *gpnum = 0; + *completed = 0; +} +EXPORT_SYMBOL_GPL(rcutorture_get_gp_data); + /* * Record the number of writer passes through the current rcutorture test. * This is also used to correlate debugfs tracing stats with the rcutorture -- 2.34.1