From c682db558e6eec10a711b0a6bcb8c35fd15f6a39 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 19 Apr 2019 07:38:27 -0700 Subject: rcutorture: Add trivial RCU implementation I have been showing off a trivial RCU implementation for non-preemptive environments for some time now: #define rcu_read_lock() #define rcu_read_unlock() #define rcu_dereference(p) READ_ONCE(p) #define rcu_assign_pointer(p, v) smp_store_release(&(p), (v)) void synchronize_rcu(void) { int cpu; for_each_online_cpu(cpu) sched_setaffinity(current->pid, cpumask_of(cpu)); } Trivial or not, as the old saying goes, "if it ain't tested, it don't work!". This commit therefore adds a "trivial" flavor to rcutorture and a corresponding TRIVIAL test scenario. This variant does not handle CPU hotplug, which is unconditionally enabled on x86 for post-v5.1-rc3 kernels, which is why the TRIVIAL.boot says "rcutorture.onoff_interval=0". This commit actually does handle CONFIG_PREEMPT=y kernels, but only because it turns back the Linux-kernel clock in order to provide these alternative definitions (or the moral equivalent thereof): #define rcu_read_lock() preempt_disable() #define rcu_read_unlock() preempt_enable() In CONFIG_PREEMPT=n kernels without debugging, these are equivalent to empty macros give or take a compiler barrier. However, the have been successfully tested with actual empty macros as well. Signed-off-by: Paul E. McKenney [ paulmck: Fix symbol issue reported by kbuild test robot . ] [ paulmck: Work around sched_setaffinity() issue noted by Andrea Parri. ] [ paulmck: Add rcutorture.shuffle_interval=0 to TRIVIAL.boot to fix interaction with shuffler task noted by Peter Zijlstra. ] Tested-by: Andrea Parri --- kernel/rcu/rcu.h | 5 +++ kernel/rcu/rcutorture.c | 45 +++++++++++++++++++++- kernel/rcu/update.c | 13 +++++++ .../selftests/rcutorture/configs/rcu/TRIVIAL | 14 +++++++ .../selftests/rcutorture/configs/rcu/TRIVIAL.boot | 3 ++ 5 files changed, 79 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/TRIVIAL create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/TRIVIAL.boot diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index 390aab20115e..5290b01de534 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -446,6 +446,7 @@ void rcu_request_urgent_qs_task(struct task_struct *t); enum rcutorture_type { RCU_FLAVOR, RCU_TASKS_FLAVOR, + RCU_TRIVIAL_FLAVOR, SRCU_FLAVOR, INVALID_RCU_FLAVOR }; @@ -479,6 +480,10 @@ void do_trace_rcu_torture_read(const char *rcutorturename, #endif #endif +#if IS_ENABLED(CONFIG_RCU_TORTURE_TEST) || IS_MODULE(CONFIG_RCU_TORTURE_TEST) +long rcutorture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask); +#endif + #ifdef CONFIG_TINY_SRCU static inline void srcutorture_get_gp_data(enum rcutorture_type test_type, diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index a3f5488a319a..6b803fb2f7ca 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -672,6 +672,47 @@ static struct rcu_torture_ops tasks_ops = { .name = "tasks" }; +/* + * Definitions for trivial CONFIG_PREEMPT=n-only torture testing. + * This implementation does not necessarily work well with CPU hotplug. + */ + +static void synchronize_rcu_trivial(void) +{ + int cpu; + + for_each_online_cpu(cpu) { + rcutorture_sched_setaffinity(current->pid, cpumask_of(cpu)); + WARN_ON_ONCE(raw_smp_processor_id() != cpu); + } +} + +static int rcu_torture_read_lock_trivial(void) __acquires(RCU) +{ + preempt_disable(); + return 0; +} + +static void rcu_torture_read_unlock_trivial(int idx) __releases(RCU) +{ + preempt_enable(); +} + +static struct rcu_torture_ops trivial_ops = { + .ttype = RCU_TRIVIAL_FLAVOR, + .init = rcu_sync_torture_init, + .readlock = rcu_torture_read_lock_trivial, + .read_delay = rcu_read_delay, /* just reuse rcu's version. */ + .readunlock = rcu_torture_read_unlock_trivial, + .get_gp_seq = rcu_no_completed, + .sync = synchronize_rcu_trivial, + .exp_sync = synchronize_rcu_trivial, + .fqs = NULL, + .stats = NULL, + .irq_capable = 1, + .name = "trivial" +}; + static unsigned long rcutorture_seq_diff(unsigned long new, unsigned long old) { if (!cur_ops->gp_diff) @@ -1789,6 +1830,8 @@ static void rcu_torture_fwd_prog_cr(void) if (READ_ONCE(rcu_fwd_emergency_stop)) return; /* Get out of the way quickly, no GP wait! */ + if (!cur_ops->call) + return; /* Can't do call_rcu() fwd prog without ->call. */ /* Loop continuously posting RCU callbacks. */ WRITE_ONCE(rcu_fwd_cb_nodelay, true); @@ -2265,7 +2308,7 @@ rcu_torture_init(void) int firsterr = 0; static struct rcu_torture_ops *torture_ops[] = { &rcu_ops, &rcu_busted_ops, &srcu_ops, &srcud_ops, - &busted_srcud_ops, &tasks_ops, + &busted_srcud_ops, &tasks_ops, &trivial_ops, }; if (!torture_init_begin(torture_type, verbose)) diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index c3bf44ba42e5..61df2bf08563 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -423,6 +423,19 @@ EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read); do { } while (0) #endif +#if IS_ENABLED(CONFIG_RCU_TORTURE_TEST) || IS_MODULE(CONFIG_RCU_TORTURE_TEST) +/* Get rcutorture access to sched_setaffinity(). */ +long rcutorture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask) +{ + int ret; + + ret = sched_setaffinity(pid, in_mask); + WARN_ONCE(ret, "%s: sched_setaffinity() returned %d\n", __func__, ret); + return ret; +} +EXPORT_SYMBOL_GPL(rcutorture_sched_setaffinity); +#endif + #ifdef CONFIG_RCU_STALL_COMMON int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */ EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress); diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TRIVIAL b/tools/testing/selftests/rcutorture/configs/rcu/TRIVIAL new file mode 100644 index 000000000000..4d8eb5bfb6f6 --- /dev/null +++ b/tools/testing/selftests/rcutorture/configs/rcu/TRIVIAL @@ -0,0 +1,14 @@ +CONFIG_SMP=y +CONFIG_NR_CPUS=8 +CONFIG_PREEMPT_NONE=y +CONFIG_PREEMPT_VOLUNTARY=n +CONFIG_PREEMPT=n +CONFIG_HZ_PERIODIC=n +CONFIG_NO_HZ_IDLE=y +CONFIG_NO_HZ_FULL=n +CONFIG_HOTPLUG_CPU=n +CONFIG_SUSPEND=n +CONFIG_HIBERNATION=n +CONFIG_DEBUG_LOCK_ALLOC=n +CONFIG_DEBUG_OBJECTS_RCU_HEAD=n +CONFIG_RCU_EXPERT=y diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TRIVIAL.boot b/tools/testing/selftests/rcutorture/configs/rcu/TRIVIAL.boot new file mode 100644 index 000000000000..7017f5f5a55f --- /dev/null +++ b/tools/testing/selftests/rcutorture/configs/rcu/TRIVIAL.boot @@ -0,0 +1,3 @@ +rcutorture.torture_type=trivial +rcutorture.onoff_interval=0 +rcutorture.shuffle_interval=0 -- cgit v1.2.3