diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 97007f4f69d4..77dd6bb48c3d 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5844,13 +5844,13 @@ Kernel parameters use a call_rcu[_hurry]() path. Please note, this is for a normal grace period. - How to enable it: + How to disable it: - echo 1 > /sys/module/rcutree/parameters/rcu_normal_wake_from_gp - or pass a boot parameter "rcutree.rcu_normal_wake_from_gp=1" + echo 0 > /sys/module/rcutree/parameters/rcu_normal_wake_from_gp + or pass a boot parameter "rcutree.rcu_normal_wake_from_gp=0" - Default is 1 if num_possible_cpus() <= 16 and it is not explicitly - disabled by the boot parameter passing 0. + Default is 1 if it is not explicitly disabled by the boot parameter + passing 0. rcuscale.gp_async= [KNL] Measure performance of asynchronous diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index bfa765132de8..5e95acc33989 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -592,11 +592,13 @@ context_unsafe( \ * lockdep checks for being in an RCU read-side critical section. This is * useful when the value of this pointer is accessed, but the pointer is * not dereferenced, for example, when testing an RCU-protected pointer - * against NULL. Although rcu_access_pointer() may also be used in cases - * where update-side locks prevent the value of the pointer from changing, - * you should instead use rcu_dereference_protected() for this use case. - * Within an RCU read-side critical section, there is little reason to - * use rcu_access_pointer(). + * against NULL. Within an RCU read-side critical section, there is little + * reason to use rcu_access_pointer(). Although rcu_access_pointer() may + * also be used in cases where update-side locks prevent the value of the + * pointer from changing, you should instead use rcu_dereference_protected() + * for this use case. It is also permissible to use rcu_access_pointer() + * within lockless updaters to obtain the old value for an atomic operation, + * for example, for cmpxchg(). * * It is usually best to test the rcu_access_pointer() return value * directly in order to avoid accidental dereferences being introduced diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 81b1938512d5..a54ce9e808b9 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -397,7 +397,7 @@ static inline struct srcu_ctr __percpu *srcu_read_lock_fast_notrace(struct srcu_ * * The same srcu_struct may be used concurrently by srcu_down_read_fast() * and srcu_read_lock_fast(). However, the same definition/initialization - * requirements called out for srcu_read_lock_safe() apply. + * requirements called out for srcu_read_lock_fast_updown() apply. */ static inline struct srcu_ctr __percpu *srcu_down_read_fast(struct srcu_struct *ssp) __acquires_shared(ssp) { diff --git a/include/linux/torture.h b/include/linux/torture.h index 1b59056c3b18..c9b47d138302 100644 --- a/include/linux/torture.h +++ b/include/linux/torture.h @@ -129,6 +129,7 @@ void _torture_stop_kthread(char *m, struct task_struct **tp); #else #define torture_preempt_schedule() do { } while (0) #endif +void torture_sched_set_normal(struct task_struct *t, int nice); #if IS_ENABLED(CONFIG_RCU_TORTURE_TEST) || IS_MODULE(CONFIG_RCU_TORTURE_TEST) || IS_ENABLED(CONFIG_LOCK_TORTURE_TEST) || IS_MODULE(CONFIG_LOCK_TORTURE_TEST) long torture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask, bool dowarn); diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 5f2848b828dc..882a158ada7b 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -572,7 +572,7 @@ static unsigned long rcu_no_completed(void) static void rcu_torture_deferred_free(struct rcu_torture *p) { - call_rcu_hurry(&p->rtort_rcu, rcu_torture_cb); + call_rcu(&p->rtort_rcu, rcu_torture_cb); } static void rcu_sync_torture_init(void) @@ -619,7 +619,7 @@ static struct rcu_torture_ops rcu_ops = { .poll_gp_state_exp = poll_state_synchronize_rcu, .cond_sync_exp = cond_synchronize_rcu_expedited, .cond_sync_exp_full = cond_synchronize_rcu_expedited_full, - .call = call_rcu_hurry, + .call = call_rcu, .cb_barrier = rcu_barrier, .fqs = rcu_force_quiescent_state, .gp_kthread_dbg = show_rcu_gp_kthreads, @@ -1145,7 +1145,7 @@ static void rcu_tasks_torture_deferred_free(struct rcu_torture *p) static void synchronize_rcu_mult_test(void) { - synchronize_rcu_mult(call_rcu_tasks, call_rcu_hurry); + synchronize_rcu_mult(call_rcu_tasks, call_rcu); } static struct rcu_torture_ops tasks_ops = { @@ -1631,6 +1631,17 @@ static void do_rtws_sync(struct torture_random_state *trsp, void (*sync)(void)) cpus_read_unlock(); } +/* + * Do an rcu_barrier() to motivate lazy callbacks during a stutter + * pause. Without this, we can get false-positives rtort_pipe_count + * splats. + */ +static void rcu_torture_writer_work(struct work_struct *work) +{ + if (cur_ops->cb_barrier) + cur_ops->cb_barrier(); +} + /* * RCU torture writer kthread. Repeatedly substitutes a new structure * for that pointed to by rcu_torture_current, freeing the old structure @@ -1651,6 +1662,7 @@ rcu_torture_writer(void *arg) int i; int idx; unsigned long j; + struct work_struct lazy_work; int oldnice = task_nice(current); struct rcu_gp_oldstate *rgo = NULL; int rgo_size = 0; @@ -1703,6 +1715,9 @@ rcu_torture_writer(void *arg) pr_alert("%s" TORTURE_FLAG " Waited %lu jiffies for boot to complete.\n", torture_type, jiffies - j); + if (IS_ENABLED(CONFIG_RCU_LAZY)) + INIT_WORK_ONSTACK(&lazy_work, rcu_torture_writer_work); + do { rcu_torture_writer_state = RTWS_FIXED_DELAY; torture_hrtimeout_us(500, 1000, &rand); @@ -1895,6 +1910,8 @@ rcu_torture_writer(void *arg) !rcu_gp_is_normal(); } rcu_torture_writer_state = RTWS_STUTTER; + if (IS_ENABLED(CONFIG_RCU_LAZY)) + queue_work(system_percpu_wq, &lazy_work); stutter_waited = stutter_wait("rcu_torture_writer"); if (stutter_waited && !atomic_read(&rcu_fwd_cb_nodelay) && @@ -1925,6 +1942,12 @@ rcu_torture_writer(void *arg) pr_alert("%s" TORTURE_FLAG " Dynamic grace-period expediting was disabled.\n", torture_type); + + if (IS_ENABLED(CONFIG_RCU_LAZY)) { + cancel_work_sync(&lazy_work); + destroy_work_on_stack(&lazy_work); + } + kfree(ulo); kfree(rgo); rcu_torture_writer_state = RTWS_STOPPING; diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 48f0d803c8e2..f4da5fad70f5 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -373,7 +373,8 @@ static void call_rcu_tasks_generic(struct rcu_head *rhp, rcu_callback_t func, // Queuing callbacks before initialization not yet supported. if (WARN_ON_ONCE(!rcu_segcblist_is_enabled(&rtpcp->cblist))) rcu_segcblist_init(&rtpcp->cblist); - needwake = (func == wakeme_after_rcu) || + needwake = (!havekthread && rcu_segcblist_empty(&rtpcp->cblist)) || + (func == wakeme_after_rcu) || (rcu_segcblist_n_cbs(&rtpcp->cblist) == rcu_task_lazy_lim); if (havekthread && !needwake && !timer_pending(&rtpcp->lazy_timer)) { if (rtp->lazy_jiffies) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 55df6d37145e..afb9e7db8f78 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -492,7 +492,7 @@ static int param_set_next_fqs_jiffies(const char *val, const struct kernel_param int ret = kstrtoul(val, 0, &j); if (!ret) { - WRITE_ONCE(*(ulong *)kp->arg, (j > HZ) ? HZ : (j ?: 1)); + WRITE_ONCE(*(ulong *)kp->arg, clamp_val(j, 1, HZ)); adjust_jiffies_till_sched_qs(); } return ret; @@ -1632,17 +1632,21 @@ static void rcu_sr_put_wait_head(struct llist_node *node) atomic_set_release(&sr_wn->inuse, 0); } -/* Enable rcu_normal_wake_from_gp automatically on small systems. */ -#define WAKE_FROM_GP_CPU_THRESHOLD 16 - -static int rcu_normal_wake_from_gp = -1; +static int rcu_normal_wake_from_gp = 1; module_param(rcu_normal_wake_from_gp, int, 0644); static struct workqueue_struct *sync_wq; +#define RCU_SR_NORMAL_LATCH_THR 64 + +/* Number of in-flight synchronize_rcu() calls queued on srs_next. */ +static atomic_long_t rcu_sr_normal_count; +static int rcu_sr_normal_latched; /* 0/1 */ + static void rcu_sr_normal_complete(struct llist_node *node) { struct rcu_synchronize *rs = container_of( (struct rcu_head *) node, struct rcu_synchronize, head); + long nr; WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && !poll_state_synchronize_rcu_full(&rs->oldstate), @@ -1650,6 +1654,15 @@ static void rcu_sr_normal_complete(struct llist_node *node) /* Finally. */ complete(&rs->completion); + nr = atomic_long_dec_return(&rcu_sr_normal_count); + WARN_ON_ONCE(nr < 0); + + /* + * Unlatch: switch back to normal path when fully + * drained and if it has been latched. + */ + if (nr == 0) + (void)cmpxchg_relaxed(&rcu_sr_normal_latched, 1, 0); } static void rcu_sr_normal_gp_cleanup_work(struct work_struct *work) @@ -1795,6 +1808,24 @@ static bool rcu_sr_normal_gp_init(void) static void rcu_sr_normal_add_req(struct rcu_synchronize *rs) { + /* + * Increment before publish to avoid a complete + * vs enqueue race on latch. + */ + long nr = atomic_long_inc_return(&rcu_sr_normal_count); + + /* + * Latch when threshold is reached. Checking for an exact match + * restricts cmpxchg() to a single context. + * + * This latch is intentionally relaxed and best-effort. Concurrent + * set/clear can race and temporarily lose the latch, which is OK + * because it only selects between the fast and fallback paths. + */ + if (nr == RCU_SR_NORMAL_LATCH_THR) + (void)cmpxchg_relaxed(&rcu_sr_normal_latched, 0, 1); + + /* Publish for the GP kthread/worker. */ llist_add((struct llist_node *) &rs->head, &rcu_state.srs_next); } @@ -2584,7 +2615,7 @@ static void rcu_do_batch(struct rcu_data *rdp) const long npj = NSEC_PER_SEC / HZ; long rrn = READ_ONCE(rcu_resched_ns); - rrn = rrn < NSEC_PER_MSEC ? NSEC_PER_MSEC : rrn > NSEC_PER_SEC ? NSEC_PER_SEC : rrn; + rrn = clamp(rrn, NSEC_PER_MSEC, NSEC_PER_SEC); tlimit = local_clock() + rrn; jlimit = jiffies + (rrn + npj + 1) / npj; jlimit_check = true; @@ -3278,14 +3309,15 @@ static void synchronize_rcu_normal(void) { struct rcu_synchronize rs; + init_rcu_head_on_stack(&rs.head); trace_rcu_sr_normal(rcu_state.name, &rs.head, TPS("request")); - if (READ_ONCE(rcu_normal_wake_from_gp) < 1) { + if (READ_ONCE(rcu_normal_wake_from_gp) < 1 || + READ_ONCE(rcu_sr_normal_latched)) { wait_rcu_gp(call_rcu_hurry); goto trace_complete_out; } - init_rcu_head_on_stack(&rs.head); init_completion(&rs.completion); /* @@ -3302,10 +3334,10 @@ static void synchronize_rcu_normal(void) /* Now we can wait. */ wait_for_completion(&rs.completion); - destroy_rcu_head_on_stack(&rs.head); trace_complete_out: trace_rcu_sr_normal(rcu_state.name, &rs.head, TPS("complete")); + destroy_rcu_head_on_stack(&rs.head); } /** @@ -4904,12 +4936,6 @@ void __init rcu_init(void) sync_wq = alloc_workqueue("sync_wq", WQ_MEM_RECLAIM | WQ_UNBOUND, 0); WARN_ON(!sync_wq); - /* Respect if explicitly disabled via a boot parameter. */ - if (rcu_normal_wake_from_gp < 0) { - if (num_possible_cpus() <= WAKE_FROM_GP_CPU_THRESHOLD) - rcu_normal_wake_from_gp = 1; - } - /* Fill in default value for rcutree.qovld boot parameter. */ /* -After- the rcu_node ->lock fields are initialized! */ if (qovld < 0) diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h index 1047b30cd46b..373b877cf171 100644 --- a/kernel/rcu/tree_nocb.h +++ b/kernel/rcu/tree_nocb.h @@ -655,7 +655,7 @@ static void nocb_gp_sleep(struct rcu_data *my_rdp, int cpu) * No-CBs GP kthreads come here to wait for additional callbacks to show up * or for grace periods to end. */ -static void nocb_gp_wait(struct rcu_data *my_rdp) +static noinline_for_stack void nocb_gp_wait(struct rcu_data *my_rdp) { bool bypass = false; int __maybe_unused cpu = my_rdp->cpu; diff --git a/kernel/torture.c b/kernel/torture.c index 62c1ac777694..77cb3589b19f 100644 --- a/kernel/torture.c +++ b/kernel/torture.c @@ -972,3 +972,19 @@ void _torture_stop_kthread(char *m, struct task_struct **tp) *tp = NULL; } EXPORT_SYMBOL_GPL(_torture_stop_kthread); + +/* + * Set the specified task's niceness value, saturating at limits. + * Saturating noisily, but saturating. + */ +void torture_sched_set_normal(struct task_struct *t, int nice) +{ + int realnice = nice; + + if (WARN_ON_ONCE(realnice > MAX_NICE)) + realnice = MAX_NICE; + if (WARN_ON_ONCE(realnice < MIN_NICE)) + realnice = MIN_NICE; + sched_set_normal(t, realnice); +} +EXPORT_SYMBOL_GPL(torture_sched_set_normal); diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl index 0492d6afc9a1..cc5bbd70cb84 100755 --- a/scripts/checkpatch.pl +++ b/scripts/checkpatch.pl @@ -865,8 +865,6 @@ our %deprecated_apis = ( "DEFINE_IDR" => "DEFINE_XARRAY", "idr_init" => "xa_init", "idr_init_base" => "xa_init_flags", - "rcu_read_lock_trace" => "rcu_read_lock_tasks_trace", - "rcu_read_unlock_trace" => "rcu_read_unlock_tasks_trace", ); #Create a search pattern for all these strings to speed up a loop below @@ -7596,12 +7594,15 @@ sub process { # Complain about RCU Tasks Trace used outside of BPF (and of course, RCU). our $rcu_trace_funcs = qr{(?x: + rcu_read_lock_tasks_trace | rcu_read_lock_trace | rcu_read_lock_trace_held | rcu_read_unlock_trace | + rcu_read_unlock_tasks_trace | call_rcu_tasks_trace | synchronize_rcu_tasks_trace | rcu_barrier_tasks_trace | + rcu_tasks_trace_expedite_current | rcu_request_urgent_qs_task )}; our $rcu_trace_paths = qr{(?x: diff --git a/tools/testing/selftests/rcutorture/bin/kvm-series.sh b/tools/testing/selftests/rcutorture/bin/kvm-series.sh index c4ee5f910931..be9412538fb8 100755 --- a/tools/testing/selftests/rcutorture/bin/kvm-series.sh +++ b/tools/testing/selftests/rcutorture/bin/kvm-series.sh @@ -1,12 +1,13 @@ #!/bin/bash # SPDX-License-Identifier: GPL-2.0+ # -# Usage: kvm-series.sh config-list commit-id-list [ kvm.sh parameters ] +# Usage: kvm-series.sh config-list commit-id-range [ kvm.sh parameters ] # -# Tests the specified list of unadorned configs ("TREE01 SRCU-P" but not -# "CFLIST" or "3*TRACE01") and an indication of a set of commits to test, -# then runs each commit through the specified list of commits using kvm.sh. -# The runs are grouped into a -series/config/commit directory tree. +# Tests the specified list of unadorned configs ("TREE01 SRCU-P" but +# not "CFLIST" or "3*TRACE01") and an indication of a range of commits +# ("v7.0-rc1..rcu/dev", but not "cd0ce7bab0408 ff74db28df623 17c52d7b31a1f") +# to test, then runs each commit through the specified list of commits using +# kvm.sh. The runs are grouped into a -series/config/commit directory tree. # Each run defaults to a duration of one minute. # # Run in top-level Linux source directory. Please note that this is in diff --git a/tools/testing/selftests/rcutorture/bin/torture.sh b/tools/testing/selftests/rcutorture/bin/torture.sh index a33ba109ef0b..f0083891ee81 100755 --- a/tools/testing/selftests/rcutorture/bin/torture.sh +++ b/tools/testing/selftests/rcutorture/bin/torture.sh @@ -184,7 +184,7 @@ do do_clocksourcewd=no do_srcu_lockdep=no ;; - --do-normal|--do-no-normal|--no-normal) + --do-normal|--do-norm|--do-no-normal|--do-no-norm|--no-normal|--no-norm) do_normal=`doyesno "$1" --do-normal` explicit_normal=yes ;;