From 3183059ad82a0daa8292daf43c325bac57daceb5 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 27 Feb 2024 15:07:25 -0800 Subject: rcu: Add lockdep checks and kernel-doc header to rcu_softirq_qs() There is some indications that rcu_softirq_qs() might be more generally used than anticipated. This commit therefore adds some lockdep assertions and some cautionary tales in a new kernel-doc header. Link: https://lore.kernel.org/all/Zd4DXTyCf17lcTfq@debian.debian/ Signed-off-by: Paul E. McKenney Cc: Eric Dumazet Cc: Jakub Kicinski Cc: "David S. Miller" Cc: Yan Zhai Cc: Signed-off-by: Uladzislau Rezki (Sony) --- kernel/rcu/tree.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) (limited to 'kernel/rcu/tree.c') diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index d9642dd06c25..2795a1457acf 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -240,8 +240,36 @@ static long rcu_get_n_cbs_cpu(int cpu) return 0; } +/** + * rcu_softirq_qs - Provide a set of RCU quiescent states in softirq processing + * + * Mark a quiescent state for RCU, Tasks RCU, and Tasks Trace RCU. + * This is a special-purpose function to be used in the softirq + * infrastructure and perhaps the occasional long-running softirq + * handler. + * + * Note that from RCU's viewpoint, a call to rcu_softirq_qs() is + * equivalent to momentarily completely enabling preemption. For + * example, given this code:: + * + * local_bh_disable(); + * do_something(); + * rcu_softirq_qs(); // A + * do_something_else(); + * local_bh_enable(); // B + * + * A call to synchronize_rcu() that began concurrently with the + * call to do_something() would be guaranteed to wait only until + * execution reached statement A. Without that rcu_softirq_qs(), + * that same synchronize_rcu() would instead be guaranteed to wait + * until execution reached statement B. + */ void rcu_softirq_qs(void) { + RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) || + lock_is_held(&rcu_lock_map) || + lock_is_held(&rcu_sched_lock_map), + "Illegal rcu_softirq_qs() in RCU read-side critical section"); rcu_qs(); rcu_preempt_deferred_qs(current); rcu_tasks_qs(current, false); -- cgit v1.2.3-59-g8ed1b From 62bb24c4b022b9ba9cf2e4a72f6cd8c3086f0cf8 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 7 Mar 2024 15:01:54 -0800 Subject: rcu: Remove redundant READ_ONCE() of rcu_state.gp_flags in tree.c Although it is functionally OK to do READ_ONCE() of a variable that cannot change, it is confusing and at best an accident waiting to happen. This commit therefore removes a number of READ_ONCE(rcu_state.gp_flags) instances from kernel/rcu/tree.c that are not needed due to updates to this field being excluded by virtue of holding the root rcu_node structure's ->lock. Reported-by: Linus Torvalds Closes: https://lore.kernel.org/lkml/4857c5ef-bd8f-4670-87ac-0600a1699d05@paulmck-laptop/T/#mccb23c2a4902da4d3c750165329f8de056903c58 Reported-by: Julia Lawall Closes: https://lore.kernel.org/lkml/4857c5ef-bd8f-4670-87ac-0600a1699d05@paulmck-laptop/T/#md1b5c026584f9c3c7b0fbc9240dd7de584597b73 Signed-off-by: Paul E. McKenney Signed-off-by: Uladzislau Rezki (Sony) --- kernel/rcu/tree.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) (limited to 'kernel/rcu/tree.c') diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 2795a1457acf..559f2d0d271f 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1463,7 +1463,7 @@ static noinline_for_stack bool rcu_gp_init(void) WRITE_ONCE(rcu_state.gp_activity, jiffies); raw_spin_lock_irq_rcu_node(rnp); - if (!READ_ONCE(rcu_state.gp_flags)) { + if (!rcu_state.gp_flags) { /* Spurious wakeup, tell caller to go back to sleep. */ raw_spin_unlock_irq_rcu_node(rnp); return false; @@ -1648,8 +1648,7 @@ static void rcu_gp_fqs(bool first_time) /* Clear flag to prevent immediate re-entry. */ if (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) { raw_spin_lock_irq_rcu_node(rnp); - WRITE_ONCE(rcu_state.gp_flags, - READ_ONCE(rcu_state.gp_flags) & ~RCU_GP_FLAG_FQS); + WRITE_ONCE(rcu_state.gp_flags, rcu_state.gp_flags & ~RCU_GP_FLAG_FQS); raw_spin_unlock_irq_rcu_node(rnp); } } @@ -1910,8 +1909,7 @@ static void rcu_report_qs_rsp(unsigned long flags) { raw_lockdep_assert_held_rcu_node(rcu_get_root()); WARN_ON_ONCE(!rcu_gp_in_progress()); - WRITE_ONCE(rcu_state.gp_flags, - READ_ONCE(rcu_state.gp_flags) | RCU_GP_FLAG_FQS); + WRITE_ONCE(rcu_state.gp_flags, rcu_state.gp_flags | RCU_GP_FLAG_FQS); raw_spin_unlock_irqrestore_rcu_node(rcu_get_root(), flags); rcu_gp_kthread_wake(); } @@ -2426,8 +2424,7 @@ void rcu_force_quiescent_state(void) raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags); return; /* Someone beat us to it. */ } - WRITE_ONCE(rcu_state.gp_flags, - READ_ONCE(rcu_state.gp_flags) | RCU_GP_FLAG_FQS); + WRITE_ONCE(rcu_state.gp_flags, rcu_state.gp_flags | RCU_GP_FLAG_FQS); raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags); rcu_gp_kthread_wake(); } -- cgit v1.2.3-59-g8ed1b From 09e077cf22c4302ab4ca7932f56c5a8b20c9e32b Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 7 Mar 2024 20:14:55 -0800 Subject: rcu: Mark loads from rcu_state.n_online_cpus The rcu_state.n_online_cpus value is only ever updated by CPU-hotplug operations, which are serialized. However, this value is read locklessly. This commit therefore marks those reads. While in the area, it also adds ASSERT_EXCLUSIVE_WRITER() calls just in case parallel CPU hotplug becomes a thing. Signed-off-by: Paul E. McKenney Signed-off-by: Uladzislau Rezki (Sony) --- kernel/rcu/tree.c | 4 +++- kernel/rcu/tree_stall.h | 6 ++++-- 2 files changed, 7 insertions(+), 3 deletions(-) (limited to 'kernel/rcu/tree.c') diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 559f2d0d271f..7149b2d5cdd6 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -4328,7 +4328,7 @@ EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online); // whether spinlocks may be acquired safely. static bool rcu_init_invoked(void) { - return !!rcu_state.n_online_cpus; + return !!READ_ONCE(rcu_state.n_online_cpus); } /* @@ -4538,6 +4538,7 @@ int rcutree_prepare_cpu(unsigned int cpu) raw_spin_unlock_irqrestore_rcu_node(rnp, flags); rcu_spawn_rnp_kthreads(rnp); rcu_spawn_cpu_nocb_kthread(cpu); + ASSERT_EXCLUSIVE_WRITER(rcu_state.n_online_cpus); WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus + 1); return 0; @@ -4806,6 +4807,7 @@ void rcutree_migrate_callbacks(int cpu) */ int rcutree_dead_cpu(unsigned int cpu) { + ASSERT_EXCLUSIVE_WRITER(rcu_state.n_online_cpus); WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus - 1); // Stop-machine done, so allow nohz_full to disable tick. tick_dep_clear(TICK_DEP_BIT_RCU); diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h index 62b2c4858028..8a2edf6a1ef5 100644 --- a/kernel/rcu/tree_stall.h +++ b/kernel/rcu/tree_stall.h @@ -628,7 +628,8 @@ static void print_other_cpu_stall(unsigned long gp_seq, unsigned long gps) totqlen += rcu_get_n_cbs_cpu(cpu); pr_err("\t(detected by %d, t=%ld jiffies, g=%ld, q=%lu ncpus=%d)\n", smp_processor_id(), (long)(jiffies - gps), - (long)rcu_seq_current(&rcu_state.gp_seq), totqlen, rcu_state.n_online_cpus); + (long)rcu_seq_current(&rcu_state.gp_seq), totqlen, + data_race(rcu_state.n_online_cpus)); // Diagnostic read if (ndetected) { rcu_dump_cpu_stacks(); @@ -689,7 +690,8 @@ static void print_cpu_stall(unsigned long gps) totqlen += rcu_get_n_cbs_cpu(cpu); pr_err("\t(t=%lu jiffies g=%ld q=%lu ncpus=%d)\n", jiffies - gps, - (long)rcu_seq_current(&rcu_state.gp_seq), totqlen, rcu_state.n_online_cpus); + (long)rcu_seq_current(&rcu_state.gp_seq), totqlen, + data_race(rcu_state.n_online_cpus)); // Diagnostic read rcu_check_gp_kthread_expired_fqs_timer(); rcu_check_gp_kthread_starvation(); -- cgit v1.2.3-59-g8ed1b From ae2b217ab542d0db0ca1a6de4f442201a1982f00 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 8 Mar 2024 11:15:01 -0800 Subject: rcu: Make hotplug operations track GP state, not flags Currently, there are rcu_data structure fields named ->rcu_onl_gp_seq and ->rcu_ofl_gp_seq that track the rcu_state.gp_flags field at the time of the corresponding CPU's last online or offline operation, respectively. However, this information is not particularly useful. It would be better to instead track the grace period state kept in rcu_state.gp_state. This would also be consistent with the initialization in rcu_boot_init_percpu_data(), which is to RCU_GP_CLEANED (an rcu_state.gp_state value), and also with the diagnostics in rcu_implicit_dynticks_qs(), whose format is consistent with an integer, not a bitmask. This commit therefore makes this change and changes the names to ->rcu_onl_gp_flags and ->rcu_ofl_gp_flags, respectively. Signed-off-by: Paul E. McKenney Signed-off-by: Uladzislau Rezki (Sony) --- kernel/rcu/tree.c | 12 ++++++------ kernel/rcu/tree.h | 4 ++-- kernel/rcu/tree_plugin.h | 4 ++-- 3 files changed, 10 insertions(+), 10 deletions(-) (limited to 'kernel/rcu/tree.c') diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 7149b2d5cdd6..306f55b81d10 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -841,8 +841,8 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) __func__, rnp1->grplo, rnp1->grphi, rnp1->qsmask, rnp1->qsmaskinit, rnp1->qsmaskinitnext, rnp1->rcu_gp_init_mask); pr_info("%s %d: %c online: %ld(%d) offline: %ld(%d)\n", __func__, rdp->cpu, ".o"[rcu_rdp_cpu_online(rdp)], - (long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_flags, - (long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_flags); + (long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_state, + (long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_state); return 1; /* Break things loose after complaining. */ } @@ -4420,9 +4420,9 @@ rcu_boot_init_percpu_data(int cpu) WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(cpu))); rdp->barrier_seq_snap = rcu_state.barrier_sequence; rdp->rcu_ofl_gp_seq = rcu_state.gp_seq; - rdp->rcu_ofl_gp_flags = RCU_GP_CLEANED; + rdp->rcu_ofl_gp_state = RCU_GP_CLEANED; rdp->rcu_onl_gp_seq = rcu_state.gp_seq; - rdp->rcu_onl_gp_flags = RCU_GP_CLEANED; + rdp->rcu_onl_gp_state = RCU_GP_CLEANED; rdp->last_sched_clock = jiffies; rdp->cpu = cpu; rcu_boot_init_nocb_percpu_data(rdp); @@ -4682,7 +4682,7 @@ void rcutree_report_cpu_starting(unsigned int cpu) ASSERT_EXCLUSIVE_WRITER(rcu_state.ncpus); rcu_gpnum_ovf(rnp, rdp); /* Offline-induced counter wrap? */ rdp->rcu_onl_gp_seq = READ_ONCE(rcu_state.gp_seq); - rdp->rcu_onl_gp_flags = READ_ONCE(rcu_state.gp_flags); + rdp->rcu_onl_gp_state = READ_ONCE(rcu_state.gp_state); /* An incoming CPU should never be blocking a grace period. */ if (WARN_ON_ONCE(rnp->qsmask & mask)) { /* RCU waiting on incoming CPU? */ @@ -4733,7 +4733,7 @@ void rcutree_report_cpu_dead(void) arch_spin_lock(&rcu_state.ofl_lock); raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */ rdp->rcu_ofl_gp_seq = READ_ONCE(rcu_state.gp_seq); - rdp->rcu_ofl_gp_flags = READ_ONCE(rcu_state.gp_flags); + rdp->rcu_ofl_gp_state = READ_ONCE(rcu_state.gp_state); if (rnp->qsmask & mask) { /* RCU waiting on outgoing CPU? */ /* Report quiescent state -before- changing ->qsmaskinitnext! */ rcu_disable_urgency_upon_qs(rdp); diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index df48160b3136..ff4d8b60554b 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -273,9 +273,9 @@ struct rcu_data { bool rcu_iw_pending; /* Is ->rcu_iw pending? */ unsigned long rcu_iw_gp_seq; /* ->gp_seq associated with ->rcu_iw. */ unsigned long rcu_ofl_gp_seq; /* ->gp_seq at last offline. */ - short rcu_ofl_gp_flags; /* ->gp_flags at last offline. */ + short rcu_ofl_gp_state; /* ->gp_state at last offline. */ unsigned long rcu_onl_gp_seq; /* ->gp_seq at last online. */ - short rcu_onl_gp_flags; /* ->gp_flags at last online. */ + short rcu_onl_gp_state; /* ->gp_state at last online. */ unsigned long last_fqs_resched; /* Time of last rcu_resched(). */ unsigned long last_sched_clock; /* Jiffies of last rcu_sched_clock_irq(). */ struct rcu_snap_record snap_record; /* Snapshot of core stats at half of */ diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 36a8b5dbf5b5..340bbefe5f65 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -805,8 +805,8 @@ dump_blkd_tasks(struct rcu_node *rnp, int ncheck) rdp = per_cpu_ptr(&rcu_data, cpu); pr_info("\t%d: %c online: %ld(%d) offline: %ld(%d)\n", cpu, ".o"[rcu_rdp_cpu_online(rdp)], - (long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_flags, - (long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_flags); + (long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_state, + (long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_state); } } -- cgit v1.2.3-59-g8ed1b From 988f569ae041ccc93a79d98d1b0043dff4d7e9b7 Mon Sep 17 00:00:00 2001 From: "Uladzislau Rezki (Sony)" Date: Fri, 8 Mar 2024 18:34:05 +0100 Subject: rcu: Reduce synchronize_rcu() latency A call to a synchronize_rcu() can be optimized from a latency point of view. Workloads which depend on this can benefit of it. The delay of wakeme_after_rcu() callback, which unblocks a waiter, depends on several factors: - how fast a process of offloading is started. Combination of: - !CONFIG_RCU_NOCB_CPU/CONFIG_RCU_NOCB_CPU; - !CONFIG_RCU_LAZY/CONFIG_RCU_LAZY; - other. - when started, invoking path is interrupted due to: - time limit; - need_resched(); - if limit is reached. - where in a nocb list it is located; - how fast previous callbacks completed; Example: 1. On our embedded devices i can easily trigger the scenario when it is a last in the list out of ~3600 callbacks: <...>-29 [001] d..1. 21950.145313: rcu_batch_start: rcu_preempt CBs=3613 bl=28 ... <...>-29 [001] ..... 21950.152578: rcu_invoke_callback: rcu_preempt rhp=00000000b2d6dee8 func=__free_vm_area_struct.cfi_jt <...>-29 [001] ..... 21950.152579: rcu_invoke_callback: rcu_preempt rhp=00000000a446f607 func=__free_vm_area_struct.cfi_jt <...>-29 [001] ..... 21950.152580: rcu_invoke_callback: rcu_preempt rhp=00000000a5cab03b func=__free_vm_area_struct.cfi_jt <...>-29 [001] ..... 21950.152581: rcu_invoke_callback: rcu_preempt rhp=0000000013b7e5ee func=__free_vm_area_struct.cfi_jt <...>-29 [001] ..... 21950.152582: rcu_invoke_callback: rcu_preempt rhp=000000000a8ca6f9 func=__free_vm_area_struct.cfi_jt <...>-29 [001] ..... 21950.152583: rcu_invoke_callback: rcu_preempt rhp=000000008f162ca8 func=wakeme_after_rcu.cfi_jt <...>-29 [001] d..1. 21950.152625: rcu_batch_end: rcu_preempt CBs-invoked=3612 idle=.... 2. We use cpuset/cgroup to classify tasks and assign them into different cgroups. For example "backgrond" group which binds tasks only to little CPUs or "foreground" which makes use of all CPUs. Tasks can be migrated between groups by a request if an acceleration is needed. See below an example how "surfaceflinger" task gets migrated. Initially it is located in the "system-background" cgroup which allows to run only on little cores. In order to speed it up it can be temporary moved into "foreground" cgroup which allows to use big/all CPUs: cgroup_attach_task(): -> cgroup_migrate_execute() -> cpuset_can_attach() -> percpu_down_write() -> rcu_sync_enter() -> synchronize_rcu() -> now move tasks to the new cgroup. -> cgroup_migrate_finish() rcuop/1-29 [000] ..... 7030.528570: rcu_invoke_callback: rcu_preempt rhp=00000000461605e0 func=wakeme_after_rcu.cfi_jt PERFD-SERVER-1855 [000] d..1. 7030.530293: cgroup_attach_task: dst_root=3 dst_id=22 dst_level=1 dst_path=/foreground pid=1900 comm=surfaceflinger TimerDispatch-2768 [002] d..5. 7030.537542: sched_migrate_task: comm=surfaceflinger pid=1900 prio=98 orig_cpu=0 dest_cpu=4 "Boosting a task" depends on synchronize_rcu() latency: - first trace shows a completion of synchronize_rcu(); - second shows attaching a task to a new group; - last shows a final step when migration occurs. 3. To address this drawback, maintain a separate track that consists of synchronize_rcu() callers only. After completion of a grace period users are deferred to a dedicated worker to process requests. 4. This patch reduces the latency of synchronize_rcu() approximately by ~30-40% on synthetic tests. The real test case, camera launch time, shows(time is in milliseconds): 1-run 542 vs 489 improvement 9% 2-run 540 vs 466 improvement 13% 3-run 518 vs 468 improvement 9% 4-run 531 vs 457 improvement 13% 5-run 548 vs 475 improvement 13% 6-run 509 vs 484 improvement 4% Synthetic test(no "noise" from other callbacks): Hardware: x86_64 64 CPUs, 64GB of memory Linux-6.6 - 10K tasks(simultaneous); - each task does(1000 loops) synchronize_rcu(); kfree(p); default: CONFIG_RCU_NOCB_CPU: takes 54 seconds to complete all users; patch: CONFIG_RCU_NOCB_CPU: takes 35 seconds to complete all users. Running 60K gives approximately same results on my setup. Please note it is without any interaction with another type of callbacks, otherwise it will impact a lot a default case. 5. By default it is disabled. To enable this perform one of the below sequence: echo 1 > /sys/module/rcutree/parameters/rcu_normal_wake_from_gp or pass a boot parameter "rcutree.rcu_normal_wake_from_gp=1" Reviewed-by: Paul E. McKenney Reviewed-by: Frederic Weisbecker Co-developed-by: Neeraj Upadhyay (AMD) Signed-off-by: Neeraj Upadhyay (AMD) Signed-off-by: Uladzislau Rezki (Sony) --- Documentation/admin-guide/kernel-parameters.txt | 14 + kernel/rcu/tree.c | 331 +++++++++++++++++++++++- kernel/rcu/tree_exp.h | 2 +- 3 files changed, 345 insertions(+), 2 deletions(-) (limited to 'kernel/rcu/tree.c') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index bb884c14b2f6..0a3b0fd1910e 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5091,6 +5091,20 @@ delay, memory pressure or callback list growing too big. + rcutree.rcu_normal_wake_from_gp= [KNL] + Reduces a latency of synchronize_rcu() call. This approach + maintains its own track of synchronize_rcu() callers, so it + does not interact with regular callbacks because it does not + use a call_rcu[_hurry]() path. Please note, this is for a + normal grace period. + + How to enable it: + + echo 1 > /sys/module/rcutree/parameters/rcu_normal_wake_from_gp + or pass a boot parameter "rcutree.rcu_normal_wake_from_gp=1" + + Default is 0. + rcuscale.gp_async= [KNL] Measure performance of asynchronous grace-period primitives such as call_rcu(). diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index d9642dd06c25..f65255205e44 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -75,6 +75,7 @@ #define MODULE_PARAM_PREFIX "rcutree." /* Data structures. */ +static void rcu_sr_normal_gp_cleanup_work(struct work_struct *); static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, rcu_data) = { .gpwrap = true, @@ -93,6 +94,8 @@ static struct rcu_state rcu_state = { .exp_mutex = __MUTEX_INITIALIZER(rcu_state.exp_mutex), .exp_wake_mutex = __MUTEX_INITIALIZER(rcu_state.exp_wake_mutex), .ofl_lock = __ARCH_SPIN_LOCK_UNLOCKED, + .srs_cleanup_work = __WORK_INITIALIZER(rcu_state.srs_cleanup_work, + rcu_sr_normal_gp_cleanup_work), }; /* Dump rcu_node combining tree at boot to verify correct setup. */ @@ -1422,6 +1425,282 @@ static void rcu_poll_gp_seq_end_unlocked(unsigned long *snap) raw_spin_unlock_irqrestore_rcu_node(rnp, flags); } +/* + * There is a single llist, which is used for handling + * synchronize_rcu() users' enqueued rcu_synchronize nodes. + * Within this llist, there are two tail pointers: + * + * wait tail: Tracks the set of nodes, which need to + * wait for the current GP to complete. + * done tail: Tracks the set of nodes, for which grace + * period has elapsed. These nodes processing + * will be done as part of the cleanup work + * execution by a kworker. + * + * At every grace period init, a new wait node is added + * to the llist. This wait node is used as wait tail + * for this new grace period. Given that there are a fixed + * number of wait nodes, if all wait nodes are in use + * (which can happen when kworker callback processing + * is delayed) and additional grace period is requested. + * This means, a system is slow in processing callbacks. + * + * TODO: If a slow processing is detected, a first node + * in the llist should be used as a wait-tail for this + * grace period, therefore users which should wait due + * to a slow process are handled by _this_ grace period + * and not next. + * + * Below is an illustration of how the done and wait + * tail pointers move from one set of rcu_synchronize nodes + * to the other, as grace periods start and finish and + * nodes are processed by kworker. + * + * + * a. Initial llist callbacks list: + * + * +----------+ +--------+ +-------+ + * | | | | | | + * | head |---------> | cb2 |--------->| cb1 | + * | | | | | | + * +----------+ +--------+ +-------+ + * + * + * + * b. New GP1 Start: + * + * WAIT TAIL + * | + * | + * v + * +----------+ +--------+ +--------+ +-------+ + * | | | | | | | | + * | head ------> wait |------> cb2 |------> | cb1 | + * | | | head1 | | | | | + * +----------+ +--------+ +--------+ +-------+ + * + * + * + * c. GP completion: + * + * WAIT_TAIL == DONE_TAIL + * + * DONE TAIL + * | + * | + * v + * +----------+ +--------+ +--------+ +-------+ + * | | | | | | | | + * | head ------> wait |------> cb2 |------> | cb1 | + * | | | head1 | | | | | + * +----------+ +--------+ +--------+ +-------+ + * + * + * + * d. New callbacks and GP2 start: + * + * WAIT TAIL DONE TAIL + * | | + * | | + * v v + * +----------+ +------+ +------+ +------+ +-----+ +-----+ +-----+ + * | | | | | | | | | | | | | | + * | head ------> wait |--->| cb4 |--->| cb3 |--->|wait |--->| cb2 |--->| cb1 | + * | | | head2| | | | | |head1| | | | | + * +----------+ +------+ +------+ +------+ +-----+ +-----+ +-----+ + * + * + * + * e. GP2 completion: + * + * WAIT_TAIL == DONE_TAIL + * DONE TAIL + * | + * | + * v + * +----------+ +------+ +------+ +------+ +-----+ +-----+ +-----+ + * | | | | | | | | | | | | | | + * | head ------> wait |--->| cb4 |--->| cb3 |--->|wait |--->| cb2 |--->| cb1 | + * | | | head2| | | | | |head1| | | | | + * +----------+ +------+ +------+ +------+ +-----+ +-----+ +-----+ + * + * + * While the llist state transitions from d to e, a kworker + * can start executing rcu_sr_normal_gp_cleanup_work() and + * can observe either the old done tail (@c) or the new + * done tail (@e). So, done tail updates and reads need + * to use the rel-acq semantics. If the concurrent kworker + * observes the old done tail, the newly queued work + * execution will process the updated done tail. If the + * concurrent kworker observes the new done tail, then + * the newly queued work will skip processing the done + * tail, as workqueue semantics guarantees that the new + * work is executed only after the previous one completes. + * + * f. kworker callbacks processing complete: + * + * + * DONE TAIL + * | + * | + * v + * +----------+ +--------+ + * | | | | + * | head ------> wait | + * | | | head2 | + * +----------+ +--------+ + * + */ +static bool rcu_sr_is_wait_head(struct llist_node *node) +{ + return &(rcu_state.srs_wait_nodes)[0].node <= node && + node <= &(rcu_state.srs_wait_nodes)[SR_NORMAL_GP_WAIT_HEAD_MAX - 1].node; +} + +static struct llist_node *rcu_sr_get_wait_head(void) +{ + struct sr_wait_node *sr_wn; + int i; + + for (i = 0; i < SR_NORMAL_GP_WAIT_HEAD_MAX; i++) { + sr_wn = &(rcu_state.srs_wait_nodes)[i]; + + if (!atomic_cmpxchg_acquire(&sr_wn->inuse, 0, 1)) + return &sr_wn->node; + } + + return NULL; +} + +static void rcu_sr_put_wait_head(struct llist_node *node) +{ + struct sr_wait_node *sr_wn = container_of(node, struct sr_wait_node, node); + + atomic_set_release(&sr_wn->inuse, 0); +} + +/* Disabled by default. */ +static int rcu_normal_wake_from_gp; +module_param(rcu_normal_wake_from_gp, int, 0644); + +static void rcu_sr_normal_complete(struct llist_node *node) +{ + struct rcu_synchronize *rs = container_of( + (struct rcu_head *) node, struct rcu_synchronize, head); + unsigned long oldstate = (unsigned long) rs->head.func; + + WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && + !poll_state_synchronize_rcu(oldstate), + "A full grace period is not passed yet: %lu", + rcu_seq_diff(get_state_synchronize_rcu(), oldstate)); + + /* Finally. */ + complete(&rs->completion); +} + +static void rcu_sr_normal_gp_cleanup_work(struct work_struct *work) +{ + struct llist_node *done, *rcu, *next, *head; + + /* + * This work execution can potentially execute + * while a new done tail is being updated by + * grace period kthread in rcu_sr_normal_gp_cleanup(). + * So, read and updates of done tail need to + * follow acq-rel semantics. + * + * Given that wq semantics guarantees that a single work + * cannot execute concurrently by multiple kworkers, + * the done tail list manipulations are protected here. + */ + done = smp_load_acquire(&rcu_state.srs_done_tail); + if (!done) + return; + + WARN_ON_ONCE(!rcu_sr_is_wait_head(done)); + head = done->next; + done->next = NULL; + + /* + * The dummy node, which is pointed to by the + * done tail which is acq-read above is not removed + * here. This allows lockless additions of new + * rcu_synchronize nodes in rcu_sr_normal_add_req(), + * while the cleanup work executes. The dummy + * nodes is removed, in next round of cleanup + * work execution. + */ + llist_for_each_safe(rcu, next, head) { + if (!rcu_sr_is_wait_head(rcu)) { + rcu_sr_normal_complete(rcu); + continue; + } + + rcu_sr_put_wait_head(rcu); + } +} + +/* + * Helper function for rcu_gp_cleanup(). + */ +static void rcu_sr_normal_gp_cleanup(void) +{ + struct llist_node *wait_tail; + + wait_tail = rcu_state.srs_wait_tail; + if (wait_tail == NULL) + return; + + rcu_state.srs_wait_tail = NULL; + ASSERT_EXCLUSIVE_WRITER(rcu_state.srs_wait_tail); + + // concurrent sr_normal_gp_cleanup work might observe this update. + smp_store_release(&rcu_state.srs_done_tail, wait_tail); + ASSERT_EXCLUSIVE_WRITER(rcu_state.srs_done_tail); + + schedule_work(&rcu_state.srs_cleanup_work); +} + +/* + * Helper function for rcu_gp_init(). + */ +static bool rcu_sr_normal_gp_init(void) +{ + struct llist_node *first; + struct llist_node *wait_head; + bool start_new_poll = false; + + first = READ_ONCE(rcu_state.srs_next.first); + if (!first || rcu_sr_is_wait_head(first)) + return start_new_poll; + + wait_head = rcu_sr_get_wait_head(); + if (!wait_head) { + // Kick another GP to retry. + start_new_poll = true; + return start_new_poll; + } + + /* Inject a wait-dummy-node. */ + llist_add(wait_head, &rcu_state.srs_next); + + /* + * A waiting list of rcu_synchronize nodes should be empty on + * this step, since a GP-kthread, rcu_gp_init() -> gp_cleanup(), + * rolls it over. If not, it is a BUG, warn a user. + */ + WARN_ON_ONCE(rcu_state.srs_wait_tail != NULL); + rcu_state.srs_wait_tail = wait_head; + ASSERT_EXCLUSIVE_WRITER(rcu_state.srs_wait_tail); + + return start_new_poll; +} + +static void rcu_sr_normal_add_req(struct rcu_synchronize *rs) +{ + llist_add((struct llist_node *) &rs->head, &rcu_state.srs_next); +} + /* * Initialize a new grace period. Return false if no grace period required. */ @@ -1432,6 +1711,7 @@ static noinline_for_stack bool rcu_gp_init(void) unsigned long mask; struct rcu_data *rdp; struct rcu_node *rnp = rcu_get_root(); + bool start_new_poll; WRITE_ONCE(rcu_state.gp_activity, jiffies); raw_spin_lock_irq_rcu_node(rnp); @@ -1456,10 +1736,24 @@ static noinline_for_stack bool rcu_gp_init(void) /* Record GP times before starting GP, hence rcu_seq_start(). */ rcu_seq_start(&rcu_state.gp_seq); ASSERT_EXCLUSIVE_WRITER(rcu_state.gp_seq); + start_new_poll = rcu_sr_normal_gp_init(); trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("start")); rcu_poll_gp_seq_start(&rcu_state.gp_seq_polled_snap); raw_spin_unlock_irq_rcu_node(rnp); + /* + * The "start_new_poll" is set to true, only when this GP is not able + * to handle anything and there are outstanding users. It happens when + * the rcu_sr_normal_gp_init() function was not able to insert a dummy + * separator to the llist, because there were no left any dummy-nodes. + * + * Number of dummy-nodes is fixed, it could be that we are run out of + * them, if so we start a new pool request to repeat a try. It is rare + * and it means that a system is doing a slow processing of callbacks. + */ + if (start_new_poll) + (void) start_poll_synchronize_rcu(); + /* * Apply per-leaf buffered online and offline operations to * the rcu_node tree. Note that this new grace period need not @@ -1825,6 +2119,9 @@ static noinline void rcu_gp_cleanup(void) } raw_spin_unlock_irq_rcu_node(rnp); + // Make synchronize_rcu() users aware of the end of old grace period. + rcu_sr_normal_gp_cleanup(); + // If strict, make all CPUs aware of the end of the old grace period. if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) on_each_cpu(rcu_strict_gp_boundary, NULL, 0); @@ -3559,6 +3856,38 @@ static int rcu_blocking_is_gp(void) return true; } +/* + * Helper function for the synchronize_rcu() API. + */ +static void synchronize_rcu_normal(void) +{ + struct rcu_synchronize rs; + + if (!READ_ONCE(rcu_normal_wake_from_gp)) { + wait_rcu_gp(call_rcu_hurry); + return; + } + + init_rcu_head_on_stack(&rs.head); + init_completion(&rs.completion); + + /* + * This code might be preempted, therefore take a GP + * snapshot before adding a request. + */ + if (IS_ENABLED(CONFIG_PROVE_RCU)) + rs.head.func = (void *) get_state_synchronize_rcu(); + + rcu_sr_normal_add_req(&rs); + + /* Kick a GP and start waiting. */ + (void) start_poll_synchronize_rcu(); + + /* Now we can wait. */ + wait_for_completion(&rs.completion); + destroy_rcu_head_on_stack(&rs.head); +} + /** * synchronize_rcu - wait until a grace period has elapsed. * @@ -3610,7 +3939,7 @@ void synchronize_rcu(void) if (rcu_gp_is_expedited()) synchronize_rcu_expedited(); else - wait_rcu_gp(call_rcu_hurry); + synchronize_rcu_normal(); return; } diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index 6b83537480b1..8a1d9c8bd9f7 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -930,7 +930,7 @@ void synchronize_rcu_expedited(void) /* If expedited grace periods are prohibited, fall back to normal. */ if (rcu_gp_is_normal()) { - wait_rcu_gp(call_rcu_hurry); + synchronize_rcu_normal(); return; } -- cgit v1.2.3-59-g8ed1b From 2053937a310a3982de9d33af3db2dbd2b32b66e4 Mon Sep 17 00:00:00 2001 From: "Uladzislau Rezki (Sony)" Date: Fri, 8 Mar 2024 18:34:06 +0100 Subject: rcu: Add a trace event for synchronize_rcu_normal() Add an rcu_sr_normal() trace event. It takes three arguments first one is the name of RCU flavour, second one is a user id which triggeres synchronize_rcu_normal() and last one is an event. There are two traces in the synchronize_rcu_normal(). On entry, when a new request is registered and on exit point when request is completed. Please note, CONFIG_RCU_TRACE=y is required to activate traces. Reviewed-by: Paul E. McKenney Signed-off-by: Uladzislau Rezki (Sony) --- include/trace/events/rcu.h | 27 +++++++++++++++++++++++++++ kernel/rcu/tree.c | 7 ++++++- 2 files changed, 33 insertions(+), 1 deletion(-) (limited to 'kernel/rcu/tree.c') diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h index 2ef9c719772a..31b3e0d3e65f 100644 --- a/include/trace/events/rcu.h +++ b/include/trace/events/rcu.h @@ -707,6 +707,33 @@ TRACE_EVENT_RCU(rcu_invoke_kfree_bulk_callback, __entry->rcuname, __entry->p, __entry->nr_records) ); +/* + * Tracepoint for a normal synchronize_rcu() states. The first argument + * is the RCU flavor, the second argument is a pointer to rcu_head the + * last one is an event. + */ +TRACE_EVENT_RCU(rcu_sr_normal, + + TP_PROTO(const char *rcuname, struct rcu_head *rhp, const char *srevent), + + TP_ARGS(rcuname, rhp, srevent), + + TP_STRUCT__entry( + __field(const char *, rcuname) + __field(void *, rhp) + __field(const char *, srevent) + ), + + TP_fast_assign( + __entry->rcuname = rcuname; + __entry->rhp = rhp; + __entry->srevent = srevent; + ), + + TP_printk("%s rhp=0x%p event=%s", + __entry->rcuname, __entry->rhp, __entry->srevent) +); + /* * Tracepoint for exiting rcu_do_batch after RCU callbacks have been * invoked. The first argument is the name of the RCU flavor, diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index f65255205e44..2e1c5be6d64b 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3863,9 +3863,11 @@ static void synchronize_rcu_normal(void) { struct rcu_synchronize rs; + trace_rcu_sr_normal(rcu_state.name, &rs.head, TPS("request")); + if (!READ_ONCE(rcu_normal_wake_from_gp)) { wait_rcu_gp(call_rcu_hurry); - return; + goto trace_complete_out; } init_rcu_head_on_stack(&rs.head); @@ -3886,6 +3888,9 @@ 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")); } /** -- cgit v1.2.3-59-g8ed1b From 462df2f543ae360e79fcaa1b498d2a1a0c2a5b63 Mon Sep 17 00:00:00 2001 From: "Uladzislau Rezki (Sony)" Date: Fri, 8 Mar 2024 18:34:07 +0100 Subject: rcu: Support direct wake-up of synchronize_rcu() users This patch introduces a small enhancement which allows to do a direct wake-up of synchronize_rcu() callers. It occurs after a completion of grace period, thus by the gp-kthread. Number of clients is limited by the hard-coded maximum allowed threshold. The remaining part, if still exists is deferred to a main worker. Link: https://lore.kernel.org/lkml/Zd0ZtNu+Rt0qXkfS@lothringen/ Reviewed-by: Paul E. McKenney Signed-off-by: Uladzislau Rezki (Sony) --- kernel/rcu/tree.c | 24 +++++++++++++++++++++++- kernel/rcu/tree.h | 6 ++++++ 2 files changed, 29 insertions(+), 1 deletion(-) (limited to 'kernel/rcu/tree.c') diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 2e1c5be6d64b..2a270abade4d 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1645,7 +1645,8 @@ static void rcu_sr_normal_gp_cleanup_work(struct work_struct *work) */ static void rcu_sr_normal_gp_cleanup(void) { - struct llist_node *wait_tail; + struct llist_node *wait_tail, *next, *rcu; + int done = 0; wait_tail = rcu_state.srs_wait_tail; if (wait_tail == NULL) @@ -1653,11 +1654,32 @@ static void rcu_sr_normal_gp_cleanup(void) rcu_state.srs_wait_tail = NULL; ASSERT_EXCLUSIVE_WRITER(rcu_state.srs_wait_tail); + WARN_ON_ONCE(!rcu_sr_is_wait_head(wait_tail)); + + /* + * Process (a) and (d) cases. See an illustration. + */ + llist_for_each_safe(rcu, next, wait_tail->next) { + if (rcu_sr_is_wait_head(rcu)) + break; + + rcu_sr_normal_complete(rcu); + // It can be last, update a next on this step. + wait_tail->next = next; + + if (++done == SR_MAX_USERS_WAKE_FROM_GP) + break; + } // concurrent sr_normal_gp_cleanup work might observe this update. smp_store_release(&rcu_state.srs_done_tail, wait_tail); ASSERT_EXCLUSIVE_WRITER(rcu_state.srs_done_tail); + /* + * We schedule a work in order to perform a final processing + * of outstanding users(if still left) and releasing wait-heads + * added by rcu_sr_normal_gp_init() call. + */ schedule_work(&rcu_state.srs_cleanup_work); } diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index b942b9437438..2832787cee1d 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -315,6 +315,12 @@ do { \ __set_current_state(TASK_RUNNING); \ } while (0) +/* + * A max threshold for synchronize_rcu() users which are + * awaken directly by the rcu_gp_kthread(). Left part is + * deferred to the main worker. + */ +#define SR_MAX_USERS_WAKE_FROM_GP 5 #define SR_NORMAL_GP_WAIT_HEAD_MAX 5 struct sr_wait_node { -- cgit v1.2.3-59-g8ed1b From 0fd210baa07a9e3f15df1bc687293eafb119283a Mon Sep 17 00:00:00 2001 From: "Uladzislau Rezki (Sony)" Date: Fri, 8 Mar 2024 18:34:09 +0100 Subject: rcu: Allocate WQ with WQ_MEM_RECLAIM bit set synchronize_rcu() users have to be processed regardless of memory pressure so our private WQ needs to have at least one execution context what WQ_MEM_RECLAIM flag guarantees. Reviewed-by: Paul E. McKenney Reviewed-by: Joel Fernandes (Google) Signed-off-by: Uladzislau Rezki (Sony) --- kernel/rcu/tree.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'kernel/rcu/tree.c') diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 2a270abade4d..1d5c000e5c7a 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1582,6 +1582,7 @@ static void rcu_sr_put_wait_head(struct llist_node *node) /* Disabled by default. */ static int rcu_normal_wake_from_gp; module_param(rcu_normal_wake_from_gp, int, 0644); +static struct workqueue_struct *sync_wq; static void rcu_sr_normal_complete(struct llist_node *node) { @@ -1680,7 +1681,7 @@ static void rcu_sr_normal_gp_cleanup(void) * of outstanding users(if still left) and releasing wait-heads * added by rcu_sr_normal_gp_init() call. */ - schedule_work(&rcu_state.srs_cleanup_work); + queue_work(sync_wq, &rcu_state.srs_cleanup_work); } /* @@ -5585,6 +5586,9 @@ void __init rcu_init(void) rcu_gp_wq = alloc_workqueue("rcu_gp", WQ_MEM_RECLAIM, 0); WARN_ON(!rcu_gp_wq); + sync_wq = alloc_workqueue("sync_wq", WQ_MEM_RECLAIM, 0); + WARN_ON(!sync_wq); + /* Fill in default value for rcutree.qovld boot parameter. */ /* -After- the rcu_node ->lock fields are initialized! */ if (qovld < 0) -- cgit v1.2.3-59-g8ed1b From dddcddef1414be3ebc37a40d13fcc0f6a672ba9f Mon Sep 17 00:00:00 2001 From: Zqiang Date: Mon, 18 Mar 2024 17:34:11 +0800 Subject: rcutorture: Make rcutorture support print rcu-tasks gp state This commit make rcu-tasks related rcutorture test support rcu-tasks gp state printing when the writer stall occurs or the at the end of rcutorture test, and generate rcu_ops->get_gp_data() operation to simplify the acquisition of gp state for different types of rcutorture tests. Signed-off-by: Zqiang Signed-off-by: Paul E. McKenney Signed-off-by: Uladzislau Rezki (Sony) --- kernel/rcu/rcu.h | 20 ++++++++++---------- kernel/rcu/rcutorture.c | 26 ++++++++++++++++++-------- kernel/rcu/srcutree.c | 5 +---- kernel/rcu/tasks.h | 21 +++++++++++++++++++++ kernel/rcu/tree.c | 13 +++---------- 5 files changed, 53 insertions(+), 32 deletions(-) (limited to 'kernel/rcu/tree.c') diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index 86fce206560e..38238e595a61 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -522,12 +522,18 @@ static inline void show_rcu_tasks_gp_kthreads(void) {} #ifdef CONFIG_TASKS_RCU struct task_struct *get_rcu_tasks_gp_kthread(void); +void rcu_tasks_get_gp_data(int *flags, unsigned long *gp_seq); #endif // # ifdef CONFIG_TASKS_RCU #ifdef CONFIG_TASKS_RUDE_RCU struct task_struct *get_rcu_tasks_rude_gp_kthread(void); +void rcu_tasks_rude_get_gp_data(int *flags, unsigned long *gp_seq); #endif // # ifdef CONFIG_TASKS_RUDE_RCU +#ifdef CONFIG_TASKS_TRACE_RCU +void rcu_tasks_trace_get_gp_data(int *flags, unsigned long *gp_seq); +#endif + #ifdef CONFIG_TASKS_RCU_GENERIC void tasks_cblist_init_generic(void); #else /* #ifdef CONFIG_TASKS_RCU_GENERIC */ @@ -557,8 +563,7 @@ static inline void rcu_set_jiffies_lazy_flush(unsigned long j) { } #endif #if defined(CONFIG_TREE_RCU) -void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, - unsigned long *gp_seq); +void rcutorture_get_gp_data(int *flags, unsigned long *gp_seq); void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp, unsigned long secs, @@ -566,8 +571,7 @@ void do_trace_rcu_torture_read(const char *rcutorturename, unsigned long c); void rcu_gp_set_torture_wait(int duration); #else -static inline void rcutorture_get_gp_data(enum rcutorture_type test_type, - int *flags, unsigned long *gp_seq) +static inline void rcutorture_get_gp_data(int *flags, unsigned long *gp_seq) { *flags = 0; *gp_seq = 0; @@ -587,20 +591,16 @@ static inline void rcu_gp_set_torture_wait(int duration) { } #ifdef CONFIG_TINY_SRCU -static inline void srcutorture_get_gp_data(enum rcutorture_type test_type, - struct srcu_struct *sp, int *flags, +static inline void srcutorture_get_gp_data(struct srcu_struct *sp, int *flags, unsigned long *gp_seq) { - if (test_type != SRCU_FLAVOR) - return; *flags = 0; *gp_seq = sp->srcu_idx; } #elif defined(CONFIG_TREE_SRCU) -void srcutorture_get_gp_data(enum rcutorture_type test_type, - struct srcu_struct *sp, int *flags, +void srcutorture_get_gp_data(struct srcu_struct *sp, int *flags, unsigned long *gp_seq); #endif diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 2f43d31fb7a5..85ff8a32f75a 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -381,6 +381,7 @@ struct rcu_torture_ops { void (*gp_kthread_dbg)(void); bool (*check_boost_failed)(unsigned long gp_state, int *cpup); int (*stall_dur)(void); + void (*get_gp_data)(int *flags, unsigned long *gp_seq); long cbflood_max; int irq_capable; int can_boost; @@ -569,6 +570,7 @@ static struct rcu_torture_ops rcu_ops = { .gp_kthread_dbg = show_rcu_gp_kthreads, .check_boost_failed = rcu_check_boost_fail, .stall_dur = rcu_jiffies_till_stall_check, + .get_gp_data = rcutorture_get_gp_data, .irq_capable = 1, .can_boost = IS_ENABLED(CONFIG_RCU_BOOST), .extendables = RCUTORTURE_MAX_EXTEND, @@ -628,6 +630,11 @@ static struct srcu_struct srcu_ctld; static struct srcu_struct *srcu_ctlp = &srcu_ctl; static struct rcu_torture_ops srcud_ops; +static void srcu_get_gp_data(int *flags, unsigned long *gp_seq) +{ + srcutorture_get_gp_data(srcu_ctlp, flags, gp_seq); +} + static int srcu_torture_read_lock(void) { if (cur_ops == &srcud_ops) @@ -736,6 +743,7 @@ static struct rcu_torture_ops srcu_ops = { .call = srcu_torture_call, .cb_barrier = srcu_torture_barrier, .stats = srcu_torture_stats, + .get_gp_data = srcu_get_gp_data, .cbflood_max = 50000, .irq_capable = 1, .no_pi_lock = IS_ENABLED(CONFIG_TINY_SRCU), @@ -774,6 +782,7 @@ static struct rcu_torture_ops srcud_ops = { .call = srcu_torture_call, .cb_barrier = srcu_torture_barrier, .stats = srcu_torture_stats, + .get_gp_data = srcu_get_gp_data, .cbflood_max = 50000, .irq_capable = 1, .no_pi_lock = IS_ENABLED(CONFIG_TINY_SRCU), @@ -882,6 +891,7 @@ static struct rcu_torture_ops tasks_ops = { .call = call_rcu_tasks, .cb_barrier = rcu_barrier_tasks, .gp_kthread_dbg = show_rcu_tasks_classic_gp_kthread, + .get_gp_data = rcu_tasks_get_gp_data, .fqs = NULL, .stats = NULL, .irq_capable = 1, @@ -922,6 +932,7 @@ static struct rcu_torture_ops tasks_rude_ops = { .call = call_rcu_tasks_rude, .cb_barrier = rcu_barrier_tasks_rude, .gp_kthread_dbg = show_rcu_tasks_rude_gp_kthread, + .get_gp_data = rcu_tasks_rude_get_gp_data, .cbflood_max = 50000, .fqs = NULL, .stats = NULL, @@ -974,6 +985,7 @@ static struct rcu_torture_ops tasks_tracing_ops = { .call = call_rcu_tasks_trace, .cb_barrier = rcu_barrier_tasks_trace, .gp_kthread_dbg = show_rcu_tasks_trace_gp_kthread, + .get_gp_data = rcu_tasks_trace_get_gp_data, .cbflood_max = 50000, .fqs = NULL, .stats = NULL, @@ -2264,10 +2276,8 @@ rcu_torture_stats_print(void) int __maybe_unused flags = 0; unsigned long __maybe_unused gp_seq = 0; - rcutorture_get_gp_data(cur_ops->ttype, - &flags, &gp_seq); - srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, - &flags, &gp_seq); + if (cur_ops->get_gp_data) + cur_ops->get_gp_data(&flags, &gp_seq); wtp = READ_ONCE(writer_task); pr_alert("??? Writer stall state %s(%d) g%lu f%#x ->state %#x cpu %d\n", rcu_torture_writer_state_getname(), @@ -3390,8 +3400,8 @@ rcu_torture_cleanup(void) fakewriter_tasks = NULL; } - rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq); - srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq); + if (cur_ops->get_gp_data) + cur_ops->get_gp_data(&flags, &gp_seq); pr_alert("%s: End-test grace-period state: g%ld f%#x total-gps=%ld\n", cur_ops->name, (long)gp_seq, flags, rcutorture_seq_diff(gp_seq, start_gp_seq)); @@ -3762,8 +3772,8 @@ rcu_torture_init(void) nrealreaders = 1; } rcu_torture_print_module_parms(cur_ops, "Start of test"); - rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq); - srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq); + if (cur_ops->get_gp_data) + cur_ops->get_gp_data(&flags, &gp_seq); start_gp_seq = gp_seq; pr_alert("%s: Start-test grace-period state: g%ld f%#x\n", cur_ops->name, (long)gp_seq, flags); diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index e4d673fc30f4..bc4b58b0204e 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -1826,12 +1826,9 @@ static void process_srcu(struct work_struct *work) srcu_reschedule(ssp, curdelay); } -void srcutorture_get_gp_data(enum rcutorture_type test_type, - struct srcu_struct *ssp, int *flags, +void srcutorture_get_gp_data(struct srcu_struct *ssp, int *flags, unsigned long *gp_seq) { - if (test_type != SRCU_FLAVOR) - return; *flags = 0; *gp_seq = rcu_seq_current(&ssp->srcu_sup->srcu_gp_seq); } diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 147b5945d67a..a1af7dadc0f7 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -1178,6 +1178,13 @@ struct task_struct *get_rcu_tasks_gp_kthread(void) } EXPORT_SYMBOL_GPL(get_rcu_tasks_gp_kthread); +void rcu_tasks_get_gp_data(int *flags, unsigned long *gp_seq) +{ + *flags = 0; + *gp_seq = rcu_seq_current(&rcu_tasks.tasks_gp_seq); +} +EXPORT_SYMBOL_GPL(rcu_tasks_get_gp_data); + /* * Protect against tasklist scan blind spot while the task is exiting and * may be removed from the tasklist. Do this by adding the task to yet @@ -1358,6 +1365,13 @@ struct task_struct *get_rcu_tasks_rude_gp_kthread(void) } EXPORT_SYMBOL_GPL(get_rcu_tasks_rude_gp_kthread); +void rcu_tasks_rude_get_gp_data(int *flags, unsigned long *gp_seq) +{ + *flags = 0; + *gp_seq = rcu_seq_current(&rcu_tasks_rude.tasks_gp_seq); +} +EXPORT_SYMBOL_GPL(rcu_tasks_rude_get_gp_data); + #endif /* #ifdef CONFIG_TASKS_RUDE_RCU */ //////////////////////////////////////////////////////////////////////// @@ -2010,6 +2024,13 @@ struct task_struct *get_rcu_tasks_trace_gp_kthread(void) } EXPORT_SYMBOL_GPL(get_rcu_tasks_trace_gp_kthread); +void rcu_tasks_trace_get_gp_data(int *flags, unsigned long *gp_seq) +{ + *flags = 0; + *gp_seq = rcu_seq_current(&rcu_tasks_trace.tasks_gp_seq); +} +EXPORT_SYMBOL_GPL(rcu_tasks_trace_get_gp_data); + #else /* #ifdef CONFIG_TASKS_TRACE_RCU */ static void exit_tasks_rcu_finish_trace(struct task_struct *t) { } #endif /* #else #ifdef CONFIG_TASKS_TRACE_RCU */ diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index d9642dd06c25..60e79ed73700 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -508,17 +508,10 @@ static struct rcu_node *rcu_get_root(void) /* * Send along grace-period-related data for rcutorture diagnostics. */ -void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, - unsigned long *gp_seq) +void rcutorture_get_gp_data(int *flags, unsigned long *gp_seq) { - switch (test_type) { - case RCU_FLAVOR: - *flags = READ_ONCE(rcu_state.gp_flags); - *gp_seq = rcu_seq_current(&rcu_state.gp_seq); - break; - default: - break; - } + *flags = READ_ONCE(rcu_state.gp_flags); + *gp_seq = rcu_seq_current(&rcu_state.gp_seq); } EXPORT_SYMBOL_GPL(rcutorture_get_gp_data); -- cgit v1.2.3-59-g8ed1b