X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=urcu-call-rcu-impl.h;h=d09adb1bc431a55923d3bbeb3904939f3344e460;hp=3e947af2fd84bfd6c6843788d9f31a5ff720b876;hb=1f689e13ea7e519b1afc001e9c55a7b1b60b599f;hpb=698d07788379df492ad55767bdb84bc24d93c20f diff --git a/urcu-call-rcu-impl.h b/urcu-call-rcu-impl.h index 3e947af..d09adb1 100644 --- a/urcu-call-rcu-impl.h +++ b/urcu-call-rcu-impl.h @@ -82,12 +82,20 @@ static struct call_rcu_data *default_call_rcu_data; /* * Pointer to array of pointers to per-CPU call_rcu_data structures - * and # CPUs. + * and # CPUs. per_cpu_call_rcu_data is a RCU-protected pointer to an + * array of RCU-protected pointers to call_rcu_data. call_rcu acts as a + * RCU read-side and reads per_cpu_call_rcu_data and the per-cpu pointer + * without mutex. The call_rcu_mutex protects updates. */ static struct call_rcu_data **per_cpu_call_rcu_data; static long maxcpus; +static void maxcpus_reset(void) +{ + maxcpus = 0; +} + /* Allocate the array if it has not already been allocated. */ static void alloc_cpu_call_rcu_data(void) @@ -104,7 +112,7 @@ static void alloc_cpu_call_rcu_data(void) p = malloc(maxcpus * sizeof(*per_cpu_call_rcu_data)); if (p != NULL) { memset(p, '\0', maxcpus * sizeof(*per_cpu_call_rcu_data)); - per_cpu_call_rcu_data = p; + rcu_set_pointer(&per_cpu_call_rcu_data, p); } else { if (!warned) { fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n"); @@ -123,6 +131,10 @@ static void alloc_cpu_call_rcu_data(void) static struct call_rcu_data **per_cpu_call_rcu_data = NULL; static const long maxcpus = -1; +static void maxcpus_reset(void) +{ +} + static void alloc_cpu_call_rcu_data(void) { } @@ -321,13 +333,18 @@ static void call_rcu_data_init(struct call_rcu_data **crdpp, * CPU, returning NULL if there is none. We cannot automatically * created it because the platform we are running on might not define * sched_getcpu(). + * + * 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_cpu_call_rcu_data(int cpu) { static int warned = 0; + struct call_rcu_data **pcpu_crdp; - if (per_cpu_call_rcu_data == NULL) + pcpu_crdp = rcu_dereference(per_cpu_call_rcu_data); + if (pcpu_crdp == NULL) return NULL; if (!warned && maxcpus > 0 && (cpu < 0 || maxcpus <= cpu)) { fprintf(stderr, "[error] liburcu: get CPU # out of range\n"); @@ -335,7 +352,7 @@ struct call_rcu_data *get_cpu_call_rcu_data(int cpu) } if (cpu < 0 || maxcpus <= cpu) return NULL; - return per_cpu_call_rcu_data[cpu]; + return rcu_dereference(pcpu_crdp[cpu]); } /* @@ -409,7 +426,7 @@ int set_cpu_call_rcu_data(int cpu, struct call_rcu_data *crdp) return -EEXIST; } - per_cpu_call_rcu_data[cpu] = crdp; + rcu_set_pointer(&per_cpu_call_rcu_data[cpu], crdp); call_rcu_unlock(&call_rcu_mutex); return 0; } @@ -441,6 +458,9 @@ struct call_rcu_data *get_default_call_rcu_data(void) * structure assigned to the CPU on which the thread is running, * followed by the default call_rcu_data structure. If there is not * yet a default call_rcu_data structure, one will be created. + * + * Calls to this function and use of the returned call_rcu_data should + * be protected by RCU read-side lock. */ struct call_rcu_data *get_call_rcu_data(void) { @@ -555,6 +575,8 @@ static void wake_call_rcu_thread(struct call_rcu_data *crdp) * need the first invocation of call_rcu() to be fast, make sure * to create a call_rcu thread first. One way to accomplish this is * "get_call_rcu_data();", and another is create_all_cpu_call_rcu_data(). + * + * call_rcu must be called by registered RCU read-side threads. */ void call_rcu(struct rcu_head *head, @@ -564,10 +586,13 @@ void call_rcu(struct rcu_head *head, cds_wfq_node_init(&head->next); head->func = func; + /* Holding rcu read-side lock across use of per-cpu crdp */ + rcu_read_lock(); crdp = get_call_rcu_data(); cds_wfq_enqueue(&crdp->cbs, &head->next); uatomic_inc(&crdp->qlen); wake_call_rcu_thread(crdp); + rcu_read_unlock(); } /* @@ -619,7 +644,10 @@ void call_rcu_data_free(struct call_rcu_data *crdp) wake_call_rcu_thread(default_call_rcu_data); } + call_rcu_lock(&call_rcu_mutex); cds_list_del(&crdp->list); + call_rcu_unlock(&call_rcu_mutex); + free(crdp); } @@ -629,17 +657,37 @@ void call_rcu_data_free(struct call_rcu_data *crdp) void free_all_cpu_call_rcu_data(void) { int cpu; - struct call_rcu_data *crdp; + struct call_rcu_data **crdp; + static int warned = 0; if (maxcpus <= 0) return; + + crdp = malloc(sizeof(*crdp) * maxcpus); + if (!crdp) { + if (!warned) { + fprintf(stderr, "[error] liburcu: unable to allocate per-CPU pointer array\n"); + } + warned = 1; + } + for (cpu = 0; cpu < maxcpus; cpu++) { - crdp = get_cpu_call_rcu_data(cpu); - if (crdp == NULL) + crdp[cpu] = get_cpu_call_rcu_data(cpu); + if (crdp[cpu] == NULL) continue; set_cpu_call_rcu_data(cpu, NULL); - call_rcu_data_free(crdp); } + /* + * Wait for call_rcu sites acting as RCU readers of the + * call_rcu_data to become quiescent. + */ + synchronize_rcu(); + for (cpu = 0; cpu < maxcpus; cpu++) { + if (crdp[cpu] == NULL) + continue; + call_rcu_data_free(crdp[cpu]); + } + free(crdp); } /* @@ -674,6 +722,10 @@ void call_rcu_after_fork_child(void) /* Release the mutex. */ call_rcu_unlock(&call_rcu_mutex); + /* Do nothing when call_rcu() has not been used */ + if (cds_list_empty(&call_rcu_data_list)) + return; + /* * Allocate a new default call_rcu_data structure in order * to get a working call_rcu thread to go with it. @@ -681,6 +733,12 @@ void call_rcu_after_fork_child(void) default_call_rcu_data = NULL; (void)get_default_call_rcu_data(); + /* Cleanup call_rcu_data pointers before use */ + maxcpus_reset(); + free(per_cpu_call_rcu_data); + rcu_set_pointer(&per_cpu_call_rcu_data, NULL); + thread_call_rcu_data = NULL; + /* Dispose of all of the rest of the call_rcu_data structures. */ cds_list_for_each_entry_safe(crdp, next, &call_rcu_data_list, list) { if (crdp == default_call_rcu_data)