Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
rcutorture: Add a textbook-style trivial preemptible RCU
This commit adds a trivial textbook implementation of preemptible RCU
to rcutorture ("torture_type=trivial-preempt"), similar in spirit to the
existing "torture_type=trivial" textbook implementation of non-preemptible
RCU. Neither trivial RCU implementation has any value for production use,
and are intended only to keep Paul honest in his introductory writings
and presentations.
[ paulmck: Apply kernel test robot feedback. ]
Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
authored by
Paul E. McKenney
and committed by
Joel Fernandes
c6f4e552
7aaa8047
+112
-1
+4
include/linux/sched.h
+4
include/linux/sched.h
···
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struct srcu_ctr __percpu *trc_reader_scp;
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#endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
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#ifdef CONFIG_TRIVIAL_PREEMPT_RCU
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int rcu_trivial_preempt_nesting;
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#endif /* #ifdef CONFIG_TRIVIAL_PREEMPT_RCU */
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struct sched_info sched_info;
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struct list_head tasks;
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kernel/rcu/Kconfig.debug
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kernel/rcu/Kconfig.debug
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This has no value for production and is only for testing.
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config TRIVIAL_PREEMPT_RCU
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bool "Textbook trivial preemptible RCU in rcutorture"
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depends on RCU_EXPERT && RCU_TORTURE_TEST
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default n
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help
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This option enables a textbook preemptible RCU that is
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implemented in rcutorture. Its sole purpose is to validate
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code used in books, papers, and presentations.
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This has no value for production and is only for testing.
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endmenu # "RCU Debugging"
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kernel/rcu/rcu.h
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kernel/rcu/rcu.h
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static inline int rcu_stall_notifier_call_chain(unsigned long val, void *v) { return NOTIFY_DONE; }
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#endif // #else // #if defined(CONFIG_RCU_STALL_COMMON) && defined(CONFIG_RCU_CPU_STALL_NOTIFIER)
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#ifdef CONFIG_TRIVIAL_PREEMPT_RCU
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void synchronize_rcu_trivial_preempt(void);
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#endif // #ifdef CONFIG_TRIVIAL_PREEMPT_RCU
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#endif /* __LINUX_RCU_H */
+56
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kernel/rcu/rcutorture.c
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kernel/rcu/rcutorture.c
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.name = "trivial"
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};
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#ifdef CONFIG_TRIVIAL_PREEMPT_RCU
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/*
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* Definitions for trivial CONFIG_PREEMPT=y torture testing. This
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* implementation does not work well with large numbers of tasks or with
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* long-term preemption. Either or both get you RCU CPU stall warnings.
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*/
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static void rcu_sync_torture_init_trivial_preempt(void)
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{
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rcu_sync_torture_init();
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if (WARN_ONCE(onoff_interval || shuffle_interval, "%s: Non-zero onoff_interval (%d) or shuffle_interval (%d) breaks trivial RCU, resetting to zero", __func__, onoff_interval, shuffle_interval)) {
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onoff_interval = 0;
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shuffle_interval = 0;
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}
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}
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static int rcu_torture_read_lock_trivial_preempt(void)
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{
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struct task_struct *t = current;
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WRITE_ONCE(t->rcu_trivial_preempt_nesting, t->rcu_trivial_preempt_nesting + 1);
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smp_mb();
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return 0;
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}
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static void rcu_torture_read_unlock_trivial_preempt(int idx)
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{
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struct task_struct *t = current;
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smp_store_release(&t->rcu_trivial_preempt_nesting, t->rcu_trivial_preempt_nesting - 1);
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}
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static struct rcu_torture_ops trivial_preempt_ops = {
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.ttype = RCU_TRIVIAL_FLAVOR,
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.init = rcu_sync_torture_init_trivial_preempt,
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.readlock = rcu_torture_read_lock_trivial_preempt,
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.read_delay = rcu_read_delay, // just reuse rcu's version.
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.readunlock = rcu_torture_read_unlock_trivial_preempt,
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.readlock_held = torture_readlock_not_held,
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.get_gp_seq = rcu_no_completed,
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.sync = synchronize_rcu_trivial_preempt,
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.exp_sync = synchronize_rcu_trivial_preempt,
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.irq_capable = 0, // In theory it should be, but let's keep it trivial.
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.name = "trivial-preempt"
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};
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#define TRIVIAL_PREEMPT_OPS &trivial_preempt_ops,
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#else // #ifdef CONFIG_TRIVIAL_PREEMPT_RCU
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#define TRIVIAL_PREEMPT_OPS
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#endif // #else // #ifdef CONFIG_TRIVIAL_PREEMPT_RCU
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#ifdef CONFIG_TASKS_RCU
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/*
···
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static struct rcu_torture_ops *torture_ops[] = {
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&rcu_ops, &rcu_busted_ops, &srcu_ops, &srcud_ops, &busted_srcud_ops,
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TASKS_OPS TASKS_RUDE_OPS TASKS_TRACING_OPS
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&trivial_ops,
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&trivial_ops, TRIVIAL_PREEMPT_OPS
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};
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if (!torture_init_begin(torture_type, verbose))
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kernel/rcu/update.c
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kernel/rcu/update.c
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EXPORT_SYMBOL_GPL(torture_sched_setaffinity);
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#endif
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#if IS_ENABLED(CONFIG_TRIVIAL_PREEMPT_RCU)
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// Trivial and stupid grace-period wait. Defined here so that lockdep
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// kernels can find tasklist_lock.
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void synchronize_rcu_trivial_preempt(void)
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{
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struct task_struct *g;
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struct task_struct *t;
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smp_mb(); // Order prior accesses before grace-period start.
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rcu_read_lock(); // Protect task list.
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for_each_process_thread(g, t) {
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if (t == current)
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continue; // Don't deadlock on ourselves!
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// Order later rcu_read_lock() on other tasks after QS.
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while (smp_load_acquire(&t->rcu_trivial_preempt_nesting))
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continue;
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}
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rcu_read_unlock();
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}
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EXPORT_SYMBOL_GPL(synchronize_rcu_trivial_preempt);
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#endif // #if IS_ENABLED(CONFIG_TRIVIAL_PREEMPT_RCU)
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int rcu_cpu_stall_notifiers __read_mostly; // !0 = provide stall notifiers (rarely useful)
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EXPORT_SYMBOL_GPL(rcu_cpu_stall_notifiers);
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+12
tools/testing/selftests/rcutorture/configs/rcu/TRIVIAL-PREEMPT
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tools/testing/selftests/rcutorture/configs/rcu/TRIVIAL-PREEMPT
···
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CONFIG_SMP=y
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CONFIG_NR_CPUS=8
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CONFIG_PREEMPT_NONE=n
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CONFIG_PREEMPT_VOLUNTARY=n
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CONFIG_PREEMPT=y
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CONFIG_HZ_PERIODIC=n
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CONFIG_NO_HZ_IDLE=y
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CONFIG_NO_HZ_FULL=n
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CONFIG_DEBUG_LOCK_ALLOC=n
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CONFIG_DEBUG_OBJECTS_RCU_HEAD=n
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CONFIG_RCU_EXPERT=y
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CONFIG_TRIVIAL_PREEMPT_RCU=y