From f9da093679d86979fe9e00c90267dbc52f431d15 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Sun, 2 Oct 2011 12:53:44 -0400 Subject: [PATCH] Enhance API.txt documentation, add to Makefile as EXTRA_DIST Signed-off-by: Mathieu Desnoyers --- API.txt | 64 ++++++++++++++++++++++++++++++++++++++------ Makefile.am | 2 +- urcu-call-rcu-impl.h | 8 ++++++ urcu-call-rcu.h | 35 +++++++++++------------- 4 files changed, 81 insertions(+), 28 deletions(-) diff --git a/API.txt b/API.txt index a7cd5a2..72430f7 100644 --- a/API.txt +++ b/API.txt @@ -16,14 +16,14 @@ void rcu_read_unlock(void); End an RCU read-side critical section. -void rcu_register_thread(void) +void rcu_register_thread(void); Each thread must invoke this function before its first call to rcu_read_lock(). Threads that never call rcu_read_lock() need not invoke this function. In addition, rcu-bp ("bullet proof" RCU) does not require any thread to invoke rcu_register_thread(). -void rcu_unregister_thread(void) +void rcu_unregister_thread(void); Each thread that invokes rcu_register_thread() must invoke rcu_unregister_thread() before invoking pthread_exit() @@ -59,6 +59,9 @@ void call_rcu(struct rcu_head *head, call_rcu(&p->rcu, func); + call_rcu should be called from registered RCU read-side threads. + For the QSBR flavor, the caller should be online. + struct call_rcu_data *create_call_rcu_data(unsigned long flags, int cpu_affinity); @@ -77,6 +80,28 @@ struct call_rcu_data *get_call_rcu_data(void); Returns the handle of the current thread's call_rcu() helper thread, which might well be the default helper thread. + get_call_rcu_data should be called from registered RCU read-side + threads. For the QSBR flavor, the caller should be online. + +void call_rcu_data_free(struct call_rcu_data *crdp); + + Terminates a call_rcu() helper thread and frees its associated + data. The caller must have ensured that this thread is no longer + in use, for example, by passing NULL to set_thread_call_rcu_data() + and set_cpu_call_rcu_data() as required. + +struct call_rcu_data *get_default_call_rcu_data(void); + + Returns the handle for the default call_rcu() helper thread. + Creates it if necessary. + +struct call_rcu_data *get_cpu_call_rcu_data(int cpu); + + Returns the handle for the current cpu's call_rcu() helper + thread, or NULL if the current CPU has no helper thread + currently assigned. The call to this function and use of the + returned call_rcu_data should be protected by RCU read-side + lock. struct call_rcu_data *get_thread_call_rcu_data(void); @@ -84,6 +109,18 @@ struct call_rcu_data *get_thread_call_rcu_data(void); call_rcu() helper thread, or NULL if the current thread is instead using a per-CPU or the default helper thread. +struct call_rcu_data *get_call_rcu_data(void); + + Returns the handle for the current thread's call_rcu() helper + thread, which is either, in increasing order of preference: + per-thread hard-assigned helper thread, per-cpu helper thread, + or default helper thread. + +pthread_t get_call_rcu_thread(struct call_rcu_data *crdp); + + Returns the helper thread's pthread identifier linked to a call + rcu helper thread data. + void set_thread_call_rcu_data(struct call_rcu_data *crdp); Sets the current thread's hard-assigned call_rcu() helper to the @@ -100,7 +137,10 @@ int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp); this CPU from its helper thread. Once a CPU has been disassociated from its helper, further call_rcu() invocations that would otherwise have used this CPU's helper will instead - use the default helper. + use the default helper. The caller must wait for a grace-period + to pass between return from set_cpu_call_rcu_data() and call to + call_rcu_data_free() passing the previous call rcu data as + argument. int create_all_cpu_call_rcu_data(unsigned long flags) @@ -115,9 +155,17 @@ int create_all_cpu_call_rcu_data(unsigned long flags) then that executable will have only the single global default call_rcu() helper thread. This will suffice in most cases. -void call_rcu_data_free(struct call_rcu_data *crdp) +void free_all_cpu_call_rcu_data(void); - Terminates a call_rcu() helper thread and frees its associated - data. The caller must have ensured that this thread is no longer - in use, for example, by passing NULL to set_thread_call_rcu_data() - and set_cpu_call_rcu_data() as required. + Clean up all the per-CPU call_rcu threads. Should be paired with + create_all_cpu_call_rcu_data() to perform teardown. Note that + this function invokes synchronize_rcu() internally, so the + caller should be careful not to hold mutexes (or mutexes within a + dependency chain) that are also taken within a RCU read-side + critical section, or in a section where QSBR threads are online. + +void call_rcu_after_fork_child(void); + + Should be used as pthread_atfork() handler for programs using + call_rcu and performing fork() or clone() without a following + exec(). diff --git a/Makefile.am b/Makefile.am index 0cde84a..30c700b 100644 --- a/Makefile.am +++ b/Makefile.am @@ -21,7 +21,7 @@ EXTRA_DIST = $(top_srcdir)/urcu/arch/*.h $(top_srcdir)/urcu/uatomic/*.h \ gpl-2.0.txt lgpl-2.1.txt lgpl-relicensing.txt \ README LICENSE compat_arch_x86.c \ urcu-call-rcu-impl.h urcu-defer-impl.h \ - ChangeLog + ChangeLog API.txt if COMPAT_ARCH COMPAT=compat_arch_@ARCHTYPE@.c diff --git a/urcu-call-rcu-impl.h b/urcu-call-rcu-impl.h index 29c4e28..182e9b1 100644 --- a/urcu-call-rcu-impl.h +++ b/urcu-call-rcu-impl.h @@ -396,6 +396,10 @@ struct call_rcu_data *create_call_rcu_data(unsigned long flags, * the caller's responsibility to dispose of the removed structure. * Use get_cpu_call_rcu_data() to obtain a pointer to the old structure * (prior to NULLing it out, of course). + * + * The caller must wait for a grace-period to pass between return from + * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the + * previous call rcu data as argument. */ int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp) @@ -612,6 +616,10 @@ void call_rcu(struct rcu_head *head, * * We also silently refuse to free NULL pointers. This simplifies * the calling code. + * + * The caller must wait for a grace-period to pass between return from + * set_cpu_call_rcu_data() and call to call_rcu_data_free() passing the + * previous call rcu data as argument. */ void call_rcu_data_free(struct call_rcu_data *crdp) { diff --git a/urcu-call-rcu.h b/urcu-call-rcu.h index d00bb4a..8df44ef 100644 --- a/urcu-call-rcu.h +++ b/urcu-call-rcu.h @@ -61,34 +61,31 @@ struct rcu_head { /* * Exported functions + * + * Important: see userspace RCU API.txt for call_rcu family of functions + * usage detail, including the surrounding RCU usage required when using + * these primitives. */ -/* - * get_cpu_call_rcu_data should be called with RCU read-side lock held. - * Callers should be registered RCU read-side threads. - */ -struct call_rcu_data *get_cpu_call_rcu_data(int cpu); -pthread_t get_call_rcu_thread(struct call_rcu_data *crdp); +void call_rcu(struct rcu_head *head, + void (*func)(struct rcu_head *head)); + struct call_rcu_data *create_call_rcu_data(unsigned long flags, int cpu_affinity); -int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp); +void call_rcu_data_free(struct call_rcu_data *crdp); + struct call_rcu_data *get_default_call_rcu_data(void); -/* - * get_call_rcu_data should be called from registered RCU read-side - * threads. For the QSBR flavor, the caller should be online. - */ -struct call_rcu_data *get_call_rcu_data(void); +struct call_rcu_data *get_cpu_call_rcu_data(int cpu); struct call_rcu_data *get_thread_call_rcu_data(void); +struct call_rcu_data *get_call_rcu_data(void); +pthread_t get_call_rcu_thread(struct call_rcu_data *crdp); + void set_thread_call_rcu_data(struct call_rcu_data *crdp); +int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp); + int create_all_cpu_call_rcu_data(unsigned long flags); -/* - * call_rcu should be called from registered RCU read-side threads. - * For the QSBR flavor, the caller should be online. - */ -void call_rcu(struct rcu_head *head, - void (*func)(struct rcu_head *head)); -void call_rcu_data_free(struct call_rcu_data *crdp); void free_all_cpu_call_rcu_data(void); + void call_rcu_after_fork_child(void); #ifdef __cplusplus -- 2.34.1