diff options
| -rw-r--r-- | include/trace/events/rcu.h | 45 | ||||
| -rw-r--r-- | kernel/rcutree.c | 29 |
2 files changed, 73 insertions, 1 deletions
diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h index d274734b2aa4..5bde94d8585b 100644 --- a/include/trace/events/rcu.h +++ b/include/trace/events/rcu.h @@ -541,6 +541,50 @@ TRACE_EVENT(rcu_torture_read, __entry->rcutorturename, __entry->rhp) ); +/* + * Tracepoint for _rcu_barrier() execution. The string "s" describes + * the _rcu_barrier phase: + * "Begin": rcu_barrier_callback() started. + * "Check": rcu_barrier_callback() checking for piggybacking. + * "EarlyExit": rcu_barrier_callback() piggybacked, thus early exit. + * "Inc1": rcu_barrier_callback() piggyback check counter incremented. + * "Offline": rcu_barrier_callback() found offline CPU + * "OnlineQ": rcu_barrier_callback() found online CPU with callbacks. + * "OnlineNQ": rcu_barrier_callback() found online CPU, no callbacks. + * "IRQ": An rcu_barrier_callback() callback posted on remote CPU. + * "CB": An rcu_barrier_callback() invoked a callback, not the last. + * "LastCB": An rcu_barrier_callback() invoked the last callback. + * "Inc2": rcu_barrier_callback() piggyback check counter incremented. + * The "cpu" argument is the CPU or -1 if meaningless, the "cnt" argument + * is the count of remaining callbacks, and "done" is the piggybacking count. + */ +TRACE_EVENT(rcu_barrier, + + TP_PROTO(char *rcuname, char *s, int cpu, int cnt, unsigned long done), + + TP_ARGS(rcuname, s, cpu, cnt, done), + + TP_STRUCT__entry( + __field(char *, rcuname) + __field(char *, s) + __field(int, cpu) + __field(int, cnt) + __field(unsigned long, done) + ), + + TP_fast_assign( + __entry->rcuname = rcuname; + __entry->s = s; + __entry->cpu = cpu; + __entry->cnt = cnt; + __entry->done = done; + ), + + TP_printk("%s %s cpu %d remaining %d # %lu", + __entry->rcuname, __entry->s, __entry->cpu, __entry->cnt, + __entry->done) +); + #else /* #ifdef CONFIG_RCU_TRACE */ #define trace_rcu_grace_period(rcuname, gpnum, gpevent) do { } while (0) @@ -564,6 +608,7 @@ TRACE_EVENT(rcu_torture_read, #define trace_rcu_batch_end(rcuname, callbacks_invoked, cb, nr, iit, risk) \ do { } while (0) #define trace_rcu_torture_read(rcutorturename, rhp) do { } while (0) +#define trace_rcu_barrier(name, s, cpu, cnt, done) do { } while (0) #endif /* #else #ifdef CONFIG_RCU_TRACE */ diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 6bb5d562253f..dda43d826504 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -2260,6 +2260,17 @@ static int rcu_cpu_has_callbacks(int cpu) } /* + * Helper function for _rcu_barrier() tracing. If tracing is disabled, + * the compiler is expected to optimize this away. + */ +static void _rcu_barrier_trace(struct rcu_state *rsp, char *s, + int cpu, unsigned long done) +{ + trace_rcu_barrier(rsp->name, s, cpu, + atomic_read(&rsp->barrier_cpu_count), done); +} + +/* * RCU callback function for _rcu_barrier(). If we are last, wake * up the task executing _rcu_barrier(). */ @@ -2268,8 +2279,12 @@ static void rcu_barrier_callback(struct rcu_head *rhp) struct rcu_data *rdp = container_of(rhp, struct rcu_data, barrier_head); struct rcu_state *rsp = rdp->rsp; - if (atomic_dec_and_test(&rsp->barrier_cpu_count)) + if (atomic_dec_and_test(&rsp->barrier_cpu_count)) { + _rcu_barrier_trace(rsp, "LastCB", -1, rsp->n_barrier_done); complete(&rsp->barrier_completion); + } else { + _rcu_barrier_trace(rsp, "CB", -1, rsp->n_barrier_done); + } } /* @@ -2280,6 +2295,7 @@ static void rcu_barrier_func(void *type) struct rcu_state *rsp = type; struct rcu_data *rdp = __this_cpu_ptr(rsp->rda); + _rcu_barrier_trace(rsp, "IRQ", -1, rsp->n_barrier_done); atomic_inc(&rsp->barrier_cpu_count); rsp->call(&rdp->barrier_head, rcu_barrier_callback); } @@ -2298,6 +2314,7 @@ static void _rcu_barrier(struct rcu_state *rsp) unsigned long snap_done; init_rcu_head_on_stack(&rd.barrier_head); + _rcu_barrier_trace(rsp, "Begin", -1, snap); /* Take mutex to serialize concurrent rcu_barrier() requests. */ mutex_lock(&rsp->barrier_mutex); @@ -2315,7 +2332,9 @@ static void _rcu_barrier(struct rcu_state *rsp) * value up to the next even number and adds two before comparing. */ snap_done = ACCESS_ONCE(rsp->n_barrier_done); + _rcu_barrier_trace(rsp, "Check", -1, snap_done); if (ULONG_CMP_GE(snap_done, ((snap + 1) & ~0x1) + 2)) { + _rcu_barrier_trace(rsp, "EarlyExit", -1, snap_done); smp_mb(); /* caller's subsequent code after above check. */ mutex_unlock(&rsp->barrier_mutex); return; @@ -2328,6 +2347,7 @@ static void _rcu_barrier(struct rcu_state *rsp) */ ACCESS_ONCE(rsp->n_barrier_done)++; WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 1); + _rcu_barrier_trace(rsp, "Inc1", -1, rsp->n_barrier_done); smp_mb(); /* Order ->n_barrier_done increment with below mechanism. */ /* @@ -2364,13 +2384,19 @@ static void _rcu_barrier(struct rcu_state *rsp) preempt_disable(); rdp = per_cpu_ptr(rsp->rda, cpu); if (cpu_is_offline(cpu)) { + _rcu_barrier_trace(rsp, "Offline", cpu, + rsp->n_barrier_done); preempt_enable(); while (cpu_is_offline(cpu) && ACCESS_ONCE(rdp->qlen)) schedule_timeout_interruptible(1); } else if (ACCESS_ONCE(rdp->qlen)) { + _rcu_barrier_trace(rsp, "OnlineQ", cpu, + rsp->n_barrier_done); smp_call_function_single(cpu, rcu_barrier_func, rsp, 1); preempt_enable(); } else { + _rcu_barrier_trace(rsp, "OnlineNQ", cpu, + rsp->n_barrier_done); preempt_enable(); } } @@ -2403,6 +2429,7 @@ static void _rcu_barrier(struct rcu_state *rsp) smp_mb(); /* Keep increment after above mechanism. */ ACCESS_ONCE(rsp->n_barrier_done)++; WARN_ON_ONCE((rsp->n_barrier_done & 0x1) != 0); + _rcu_barrier_trace(rsp, "Inc2", -1, rsp->n_barrier_done); smp_mb(); /* Keep increment before caller's subsequent code. */ /* Wait for all rcu_barrier_callback() callbacks to be invoked. */ |