From f7be82093952ee4a74ffc8c729b2811f908cd9a4 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 8 Aug 2013 18:27:52 -0700 Subject: rcu: Improve grace-period start logic This commit improves grace-period start logic by checking ->gp_flags under the lock and by issuing a warning if a grace period is already in progress. Signed-off-by: Paul E. McKenney diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 32618b3..d679a52 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1297,7 +1297,7 @@ static void note_gp_changes(struct rcu_state *rsp, struct rcu_data *rdp) } /* - * Initialize a new grace period. + * Initialize a new grace period. Return 0 if no grace period required. */ static int rcu_gp_init(struct rcu_state *rsp) { @@ -1306,10 +1306,18 @@ static int rcu_gp_init(struct rcu_state *rsp) rcu_bind_gp_kthread(); raw_spin_lock_irq(&rnp->lock); + if (rsp->gp_flags == 0) { + /* Spurious wakeup, tell caller to go back to sleep. */ + raw_spin_unlock_irq(&rnp->lock); + return 0; + } rsp->gp_flags = 0; /* Clear all flags: New grace period. */ - if (rcu_gp_in_progress(rsp)) { - /* Grace period already in progress, don't start another. */ + if (WARN_ON_ONCE(rcu_gp_in_progress(rsp))) { + /* + * Grace period already in progress, don't start another. + * Not supposed to be able to happen. + */ raw_spin_unlock_irq(&rnp->lock); return 0; } @@ -1474,8 +1482,7 @@ static int __noreturn rcu_gp_kthread(void *arg) wait_event_interruptible(rsp->gp_wq, rsp->gp_flags & RCU_GP_FLAG_INIT); - if ((rsp->gp_flags & RCU_GP_FLAG_INIT) && - rcu_gp_init(rsp)) + if (rcu_gp_init(rsp)) break; cond_resched(); flush_signals(current); -- cgit v0.10.2 From 88d6df612cc3c99f56cc18461fcc531c3a145544 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 8 Aug 2013 21:44:31 -0700 Subject: rcu: Prevent spurious-wakeup DoS attack on rcu_gp_kthread() Spurious wakeups in the force-quiescent-state loop in rcu_gp_kthread() cause the timeout to be recalculated, which would prevent rcu_gp_fqs() from ever being called. This would in turn would prevent the grace period from ever ending for as long as there was at least one CPU in an extended quiescent state that had not yet passed through a quiescent state. This commit therefore avoids recalculating the timeout unless the previous pass's call to wait_event_interruptible_timeout() actually did time out, thus preventing the above scenario. Signed-off-by: Paul E. McKenney diff --git a/kernel/rcutree.c b/kernel/rcutree.c index d679a52..62b67b7 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1470,6 +1470,7 @@ static void rcu_gp_cleanup(struct rcu_state *rsp) static int __noreturn rcu_gp_kthread(void *arg) { int fqs_state; + int gf; unsigned long j; int ret; struct rcu_state *rsp = arg; @@ -1495,10 +1496,13 @@ static int __noreturn rcu_gp_kthread(void *arg) j = HZ; jiffies_till_first_fqs = HZ; } + ret = 0; for (;;) { - rsp->jiffies_force_qs = jiffies + j; + if (!ret) + rsp->jiffies_force_qs = jiffies + j; ret = wait_event_interruptible_timeout(rsp->gp_wq, - (rsp->gp_flags & RCU_GP_FLAG_FQS) || + ((gf = ACCESS_ONCE(rsp->gp_flags)) & + RCU_GP_FLAG_FQS) || (!ACCESS_ONCE(rnp->qsmask) && !rcu_preempt_blocked_readers_cgp(rnp)), j); @@ -1507,7 +1511,8 @@ static int __noreturn rcu_gp_kthread(void *arg) !rcu_preempt_blocked_readers_cgp(rnp)) break; /* If time for quiescent-state forcing, do it. */ - if (ret == 0 || (rsp->gp_flags & RCU_GP_FLAG_FQS)) { + if (ULONG_CMP_GE(jiffies, rsp->jiffies_force_qs) || + (gf & RCU_GP_FLAG_FQS)) { fqs_state = rcu_gp_fqs(rsp, fqs_state); cond_resched(); } else { -- cgit v0.10.2 From 591c6d1710cd73824057d08eda302cf2a7cfd18a Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 8 Aug 2013 22:26:23 -0700 Subject: rcu: Flag lockless access to ->gp_flags with ACCESS_ONCE() This commit applies ACCESS_ONCE() to an outside-of-lock access to ->gp_flags. Although it is hard to imagine any sane compiler messing this particular case up, the documentation benefits are substantial. Plus the definition of "sane compiler" grows ever looser. Signed-off-by: Paul E. McKenney diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 62b67b7..6d028fd 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1481,7 +1481,7 @@ static int __noreturn rcu_gp_kthread(void *arg) /* Handle grace-period start. */ for (;;) { wait_event_interruptible(rsp->gp_wq, - rsp->gp_flags & + ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_INIT); if (rcu_gp_init(rsp)) break; -- cgit v0.10.2 From 63c4db78e80407976e47bccaa2a4d8251b5a10bc Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 9 Aug 2013 12:19:29 -0700 Subject: rcu: Add tracing to rcu_gp_kthread() This commit adds tracing to the rcu_gp_kthread() function in order to help trace down hangs potentially involving this kthread. Reported-by: Clark Williams Reported-by: Carsten Emde Signed-off-by: Paul E. McKenney diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h index ee2376c..60077e12 100644 --- a/include/trace/events/rcu.h +++ b/include/trace/events/rcu.h @@ -39,15 +39,25 @@ TRACE_EVENT(rcu_utilization, #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) /* - * Tracepoint for grace-period events: starting and ending a grace - * period ("start" and "end", respectively), a CPU noting the start - * of a new grace period or the end of an old grace period ("cpustart" - * and "cpuend", respectively), a CPU passing through a quiescent - * state ("cpuqs"), a CPU coming online or going offline ("cpuonl" - * and "cpuofl", respectively), a CPU being kicked for being too - * long in dyntick-idle mode ("kick"), a CPU accelerating its new - * callbacks to RCU_NEXT_READY_TAIL ("AccReadyCB"), and a CPU - * accelerating its new callbacks to RCU_WAIT_TAIL ("AccWaitCB"). + * Tracepoint for grace-period events. Takes a string identifying the + * RCU flavor, the grace-period number, and a string identifying the + * grace-period-related event as follows: + * + * "AccReadyCB": CPU acclerates new callbacks to RCU_NEXT_READY_TAIL. + * "AccWaitCB": CPU accelerates new callbacks to RCU_WAIT_TAIL. + * "start": Start a grace period. + * "cpustart": CPU first notices a grace-period start. + * "cpuqs": CPU passes through a quiescent state. + * "cpuonl": CPU comes online. + * "cpuofl": CPU goes offline. + * "reqwait": GP kthread sleeps waiting for grace-period request. + * "reqwaitsig": GP kthread awakened by signal from reqwait state. + * "fqswait": GP kthread waiting until time to force quiescent states. + * "fqsstart": GP kthread starts forcing quiescent states. + * "fqsend": GP kthread done forcing quiescent states. + * "fqswaitsig": GP kthread awakened by signal from fqswait state. + * "end": End a grace period. + * "cpuend": CPU first notices a grace-period end. */ TRACE_EVENT(rcu_grace_period, diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 6d028fd..78d3715 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1480,6 +1480,9 @@ static int __noreturn rcu_gp_kthread(void *arg) /* Handle grace-period start. */ for (;;) { + trace_rcu_grace_period(rsp->name, + ACCESS_ONCE(rsp->gpnum), + TPS("reqwait")); wait_event_interruptible(rsp->gp_wq, ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_INIT); @@ -1487,6 +1490,9 @@ static int __noreturn rcu_gp_kthread(void *arg) break; cond_resched(); flush_signals(current); + trace_rcu_grace_period(rsp->name, + ACCESS_ONCE(rsp->gpnum), + TPS("reqwaitsig")); } /* Handle quiescent-state forcing. */ @@ -1500,6 +1506,9 @@ static int __noreturn rcu_gp_kthread(void *arg) for (;;) { if (!ret) rsp->jiffies_force_qs = jiffies + j; + trace_rcu_grace_period(rsp->name, + ACCESS_ONCE(rsp->gpnum), + TPS("fqswait")); ret = wait_event_interruptible_timeout(rsp->gp_wq, ((gf = ACCESS_ONCE(rsp->gp_flags)) & RCU_GP_FLAG_FQS) || @@ -1513,12 +1522,21 @@ static int __noreturn rcu_gp_kthread(void *arg) /* If time for quiescent-state forcing, do it. */ if (ULONG_CMP_GE(jiffies, rsp->jiffies_force_qs) || (gf & RCU_GP_FLAG_FQS)) { + trace_rcu_grace_period(rsp->name, + ACCESS_ONCE(rsp->gpnum), + TPS("fqsstart")); fqs_state = rcu_gp_fqs(rsp, fqs_state); + trace_rcu_grace_period(rsp->name, + ACCESS_ONCE(rsp->gpnum), + TPS("fqsend")); cond_resched(); } else { /* Deal with stray signal. */ cond_resched(); flush_signals(current); + trace_rcu_grace_period(rsp->name, + ACCESS_ONCE(rsp->gpnum), + TPS("fqswaitsig")); } j = jiffies_till_next_fqs; if (j > HZ) { -- cgit v0.10.2 From bb311eccbdab974639263060b8452bf304af0b0c Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 9 Aug 2013 16:02:09 -0700 Subject: rcu: Add tracing of normal (non-NOCB) grace-period requests This commit adds tracing to the normal grace-period request points. These are rcu_gp_cleanup(), which checks for the need for another grace period at the end of the previous grace period, and rcu_start_gp_advanced(), which restarts RCU's state machine after an idle period. These trace events are intended to help track down bugs where RCU remains idle despite there being work for it to do. Reported-by: Clark Williams Signed-off-by: Paul E. McKenney diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h index 60077e12..98466c6 100644 --- a/include/trace/events/rcu.h +++ b/include/trace/events/rcu.h @@ -45,6 +45,7 @@ TRACE_EVENT(rcu_utilization, * * "AccReadyCB": CPU acclerates new callbacks to RCU_NEXT_READY_TAIL. * "AccWaitCB": CPU accelerates new callbacks to RCU_WAIT_TAIL. + * "newreq": Request a new grace period. * "start": Start a grace period. * "cpustart": CPU first notices a grace-period start. * "cpuqs": CPU passes through a quiescent state. diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 78d3715..54dd6d0 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1459,8 +1459,12 @@ static void rcu_gp_cleanup(struct rcu_state *rsp) rsp->fqs_state = RCU_GP_IDLE; rdp = this_cpu_ptr(rsp->rda); rcu_advance_cbs(rsp, rnp, rdp); /* Reduce false positives below. */ - if (cpu_needs_another_gp(rsp, rdp)) + if (cpu_needs_another_gp(rsp, rdp)) { rsp->gp_flags = 1; + trace_rcu_grace_period(rsp->name, + ACCESS_ONCE(rsp->gpnum), + TPS("newreq")); + } raw_spin_unlock_irq(&rnp->lock); } @@ -1584,6 +1588,8 @@ rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, return; } rsp->gp_flags = RCU_GP_FLAG_INIT; + trace_rcu_grace_period(rsp->name, ACCESS_ONCE(rsp->gpnum), + TPS("newreq")); /* * We can't do wakeups while holding the rnp->lock, as that -- cgit v0.10.2 From 9261dd0da6c6432f08670719069449c6efe4f7a9 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 14 Aug 2013 16:24:26 -0700 Subject: rcu: Add tracing for rcuo no-CBs CPU wakeup handshake Lost wakeups from call_rcu() to the rcuo kthreads can result in hangs that are difficult to diagnose. This commit therefore adds tracing to help pin down the cause of these hangs. Reported-by: Clark Williams Reported-by: Carsten Emde Signed-off-by: Paul E. McKenney [ paulmck: Add const per kbuild test robot's advice. ] diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h index 98466c6..4301cd9 100644 --- a/include/trace/events/rcu.h +++ b/include/trace/events/rcu.h @@ -172,6 +172,42 @@ TRACE_EVENT(rcu_grace_period_init, ); /* + * Tracepoint for RCU no-CBs CPU callback handoffs. This event is intended + * to assist debugging of these handoffs. + * + * The first argument is the name of the RCU flavor, and the second is + * the number of the offloaded CPU are extracted. The third and final + * argument is a string as follows: + * + * "WakeEmpty": Wake rcuo kthread, first CB to empty list. + * "WakeOvf": Wake rcuo kthread, CB list is huge. + * "WakeNot": Don't wake rcuo kthread. + * "WakeNotPoll": Don't wake rcuo kthread because it is polling. + * "WokeEmpty": rcuo kthread woke to find empty list. + * "WokeNonEmpty": rcuo kthread woke to find non-empty list. + */ +TRACE_EVENT(rcu_nocb_wake, + + TP_PROTO(const char *rcuname, int cpu, const char *reason), + + TP_ARGS(rcuname, cpu, reason), + + TP_STRUCT__entry( + __field(const char *, rcuname) + __field(int, cpu) + __field(const char *, reason) + ), + + TP_fast_assign( + __entry->rcuname = rcuname; + __entry->cpu = cpu; + __entry->reason = reason; + ), + + TP_printk("%s %d %s", __entry->rcuname, __entry->cpu, __entry->reason) +); + +/* * Tracepoint for tasks blocking within preemptible-RCU read-side * critical sections. Track the type of RCU (which one day might * include SRCU), the grace-period number that the task is blocking @@ -667,6 +703,7 @@ TRACE_EVENT(rcu_barrier, #define trace_rcu_future_grace_period(rcuname, gpnum, completed, c, \ level, grplo, grphi, event) \ do { } while (0) +#define trace_rcu_nocb_wake(rcuname, cpu, reason) do { } while (0) #define trace_rcu_preempt_task(rcuname, pid, gpnum) do { } while (0) #define trace_rcu_unlock_preempted_task(rcuname, gpnum, pid) do { } while (0) #define trace_rcu_quiescent_state_report(rcuname, gpnum, mask, qsmask, level, \ diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index 130c97b..f4ed24b 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -2108,15 +2108,22 @@ static void __call_rcu_nocb_enqueue(struct rcu_data *rdp, /* If we are not being polled and there is a kthread, awaken it ... */ t = ACCESS_ONCE(rdp->nocb_kthread); - if (rcu_nocb_poll | !t) + if (rcu_nocb_poll | !t) { + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("WakeNotPoll")); return; + } len = atomic_long_read(&rdp->nocb_q_count); if (old_rhpp == &rdp->nocb_head) { wake_up(&rdp->nocb_wq); /* ... only if queue was empty ... */ rdp->qlen_last_fqs_check = 0; + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeEmpty")); } else if (len > rdp->qlen_last_fqs_check + qhimark) { wake_up_process(t); /* ... or if many callbacks queued. */ rdp->qlen_last_fqs_check = LONG_MAX / 2; + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeOvf")); + } else { + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeNot")); } return; } @@ -2233,10 +2240,15 @@ static int rcu_nocb_kthread(void *arg) wait_event_interruptible(rdp->nocb_wq, rdp->nocb_head); list = ACCESS_ONCE(rdp->nocb_head); if (!list) { + if (!rcu_nocb_poll) + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("WokeEmpty")); schedule_timeout_interruptible(1); flush_signals(current); continue; } + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("WokeNonEmpty")); /* * Extract queued callbacks, update counts, and wait -- cgit v0.10.2 From 756cbf6befe6f59b0b3e0967d92a66c11e2566ed Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 15 Aug 2013 10:12:12 -0700 Subject: rcu: Distinguish between NOCB and non-NOCB rcu_callback trace events One way to distinguish between NOCB and non-NOCB rcu_callback trace events is that the former always print zero for the lazy and non-lazy queue lengths. Unfortunately, this also means that we cannot see the NOCB queue lengths. This commit therefore accesses the NOCB queue lengths, but negates them. NOCB rcu_callback trace events should therefore have negative queue lengths. Signed-off-by: Paul E. McKenney [ paulmck: Match operand size per kbuild test robot's advice. ] diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index f4ed24b..24b01b6 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -2147,10 +2147,12 @@ static bool __call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *rhp, if (__is_kfree_rcu_offset((unsigned long)rhp->func)) trace_rcu_kfree_callback(rdp->rsp->name, rhp, (unsigned long)rhp->func, - rdp->qlen_lazy, rdp->qlen); + -atomic_long_read(&rdp->nocb_q_count_lazy), + -atomic_long_read(&rdp->nocb_q_count)); else trace_rcu_callback(rdp->rsp->name, rhp, - rdp->qlen_lazy, rdp->qlen); + -atomic_long_read(&rdp->nocb_q_count_lazy), + -atomic_long_read(&rdp->nocb_q_count)); return 1; } -- cgit v0.10.2 From 69a79bb12a81024d718e73c52e886907a3777b34 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 15 Aug 2013 13:23:23 -0700 Subject: rcu: Track rcu_nocb_kthread()'s sleeping and awakening This commit adds event traces to track all of rcu_nocb_kthread()'s blocking and awakening. Signed-off-by: Paul E. McKenney diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h index 4301cd9..a087d82 100644 --- a/include/trace/events/rcu.h +++ b/include/trace/events/rcu.h @@ -183,8 +183,12 @@ TRACE_EVENT(rcu_grace_period_init, * "WakeOvf": Wake rcuo kthread, CB list is huge. * "WakeNot": Don't wake rcuo kthread. * "WakeNotPoll": Don't wake rcuo kthread because it is polling. + * "Poll": Start of new polling cycle for rcu_nocb_poll. + * "Sleep": Sleep waiting for CBs for !rcu_nocb_poll. * "WokeEmpty": rcuo kthread woke to find empty list. * "WokeNonEmpty": rcuo kthread woke to find non-empty list. + * "WaitQueue": Enqueue partially done, timed wait for it to complete. + * "WokeQueue": Partial enqueue now complete. */ TRACE_EVENT(rcu_nocb_wake, diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index 24b01b6..21205b1 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -2230,6 +2230,7 @@ static void rcu_nocb_wait_gp(struct rcu_data *rdp) static int rcu_nocb_kthread(void *arg) { int c, cl; + bool firsttime = 1; struct rcu_head *list; struct rcu_head *next; struct rcu_head **tail; @@ -2238,8 +2239,15 @@ static int rcu_nocb_kthread(void *arg) /* Each pass through this loop invokes one batch of callbacks */ for (;;) { /* If not polling, wait for next batch of callbacks. */ - if (!rcu_nocb_poll) + if (!rcu_nocb_poll) { + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("Sleep")); wait_event_interruptible(rdp->nocb_wq, rdp->nocb_head); + } else if (firsttime) { + firsttime = 0; + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("Poll")); + } list = ACCESS_ONCE(rdp->nocb_head); if (!list) { if (!rcu_nocb_poll) @@ -2249,6 +2257,7 @@ static int rcu_nocb_kthread(void *arg) flush_signals(current); continue; } + firsttime = 1; trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WokeNonEmpty")); @@ -2271,7 +2280,11 @@ static int rcu_nocb_kthread(void *arg) next = list->next; /* Wait for enqueuing to complete, if needed. */ while (next == NULL && &list->next != tail) { + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("WaitQueue")); schedule_timeout_interruptible(1); + trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, + TPS("WokeQueue")); next = list->next; } debug_rcu_head_unqueue(list); -- cgit v0.10.2 From 15f5191b6acbbb38029b06284e8fd20275e7cfe8 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sun, 18 Aug 2013 11:59:25 -0700 Subject: rcu: Avoid sparse warnings in rcu_nocb_wake trace event The event-tracing macros do not like bool tracing arguments, so this commit makes them be of type char. This change has the knock-on effect of making it illegal to pass a pointer into one of these arguments, so also change rcutiny's first call to trace_rcu_batch_end() to convert from pointer to boolean, prefixing with "!!". Reported-by: kbuild test robot Signed-off-by: Paul E. McKenney diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h index a087d82..aca3822 100644 --- a/include/trace/events/rcu.h +++ b/include/trace/events/rcu.h @@ -591,17 +591,17 @@ TRACE_EVENT(rcu_invoke_kfree_callback, TRACE_EVENT(rcu_batch_end, TP_PROTO(const char *rcuname, int callbacks_invoked, - bool cb, bool nr, bool iit, bool risk), + char cb, char nr, char iit, char risk), TP_ARGS(rcuname, callbacks_invoked, cb, nr, iit, risk), TP_STRUCT__entry( __field(const char *, rcuname) __field(int, callbacks_invoked) - __field(bool, cb) - __field(bool, nr) - __field(bool, iit) - __field(bool, risk) + __field(char, cb) + __field(char, nr) + __field(char, iit) + __field(char, risk) ), TP_fast_assign( diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c index 9ed6075..80b6e27 100644 --- a/kernel/rcutiny.c +++ b/kernel/rcutiny.c @@ -273,7 +273,7 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) if (&rcp->rcucblist == rcp->donetail) { RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, 0, -1)); RCU_TRACE(trace_rcu_batch_end(rcp->name, 0, - ACCESS_ONCE(rcp->rcucblist), + !!ACCESS_ONCE(rcp->rcucblist), need_resched(), is_idle_task(current), false)); -- cgit v0.10.2