X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=src%2Flib%2Flttng-ust%2Flttng-ust-comm.c;h=7f34efe7a2f95ec9e934c0005d163bd71cd0ffcd;hb=8794c2dfa6542dbe99c8901ee553d1b43dcb7b77;hp=2a105bd7dcefe5c5cd976cb0010f2b23b2c9349e;hpb=ef9cd5c799d6a7dade15a0e1c5e18831d0ac534b;p=lttng-ust.git diff --git a/src/lib/lttng-ust/lttng-ust-comm.c b/src/lib/lttng-ust/lttng-ust-comm.c index 2a105bd7..7f34efe7 100644 --- a/src/lib/lttng-ust/lttng-ust-comm.c +++ b/src/lib/lttng-ust/lttng-ust-comm.c @@ -1,7 +1,7 @@ /* * SPDX-License-Identifier: LGPL-2.1-only * - * Copyright (C) 2011 David Goulet + * Copyright (C) 2011 EfficiOS Inc. * Copyright (C) 2011 Mathieu Desnoyers */ @@ -38,6 +38,7 @@ #include #include #include +#include #include #include "lib/lttng-ust/futex.h" #include "common/ustcomm.h" @@ -117,6 +118,28 @@ static int lttng_ust_comm_should_quit; */ int lttng_ust_loaded __attribute__((weak)); +/* + * Notes on async-signal-safety of ust lock: a few libc functions are used + * which are not strictly async-signal-safe: + * + * - pthread_setcancelstate + * - pthread_mutex_lock + * - pthread_mutex_unlock + * + * As of glibc 2.35, the implementation of pthread_setcancelstate only + * touches TLS data, and it appears to be safe to use from signal + * handlers. If the libc implementation changes, this will need to be + * revisited, and we may ask glibc to provide an async-signal-safe + * pthread_setcancelstate. + * + * As of glibc 2.35, the implementation of pthread_mutex_lock/unlock + * for fast mutexes only relies on the pthread_mutex_t structure. + * Disabling signals around all uses of this mutex ensures + * signal-safety. If the libc implementation changes and eventually uses + * other global resources, this will need to be revisited and we may + * need to implement our own mutex. + */ + /* * Return 0 on success, -1 if should quit. * The lock is taken in both cases. @@ -125,25 +148,21 @@ int lttng_ust_loaded __attribute__((weak)); int ust_lock(void) { sigset_t sig_all_blocked, orig_mask; - int ret, oldstate; + int ret; - ret = pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldstate); - if (ret) { - ERR("pthread_setcancelstate: %s", strerror(ret)); - } - if (oldstate != PTHREAD_CANCEL_ENABLE) { - ERR("pthread_setcancelstate: unexpected oldstate"); + if (lttng_ust_cancelstate_disable_push()) { + ERR("lttng_ust_cancelstate_disable_push"); } sigfillset(&sig_all_blocked); ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask); if (ret) { - ERR("pthread_sigmask: %s", strerror(ret)); + ERR("pthread_sigmask: ret=%d", ret); } if (!URCU_TLS(ust_mutex_nest)++) pthread_mutex_lock(&ust_mutex); ret = pthread_sigmask(SIG_SETMASK, &orig_mask, NULL); if (ret) { - ERR("pthread_sigmask: %s", strerror(ret)); + ERR("pthread_sigmask: ret=%d", ret); } if (lttng_ust_comm_should_quit) { return -1; @@ -161,25 +180,21 @@ int ust_lock(void) void ust_lock_nocheck(void) { sigset_t sig_all_blocked, orig_mask; - int ret, oldstate; + int ret; - ret = pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &oldstate); - if (ret) { - ERR("pthread_setcancelstate: %s", strerror(ret)); - } - if (oldstate != PTHREAD_CANCEL_ENABLE) { - ERR("pthread_setcancelstate: unexpected oldstate"); + if (lttng_ust_cancelstate_disable_push()) { + ERR("lttng_ust_cancelstate_disable_push"); } sigfillset(&sig_all_blocked); ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask); if (ret) { - ERR("pthread_sigmask: %s", strerror(ret)); + ERR("pthread_sigmask: ret=%d", ret); } if (!URCU_TLS(ust_mutex_nest)++) pthread_mutex_lock(&ust_mutex); ret = pthread_sigmask(SIG_SETMASK, &orig_mask, NULL); if (ret) { - ERR("pthread_sigmask: %s", strerror(ret)); + ERR("pthread_sigmask: ret=%d", ret); } } @@ -189,25 +204,21 @@ void ust_lock_nocheck(void) void ust_unlock(void) { sigset_t sig_all_blocked, orig_mask; - int ret, oldstate; + int ret; sigfillset(&sig_all_blocked); ret = pthread_sigmask(SIG_SETMASK, &sig_all_blocked, &orig_mask); if (ret) { - ERR("pthread_sigmask: %s", strerror(ret)); + ERR("pthread_sigmask: ret=%d", ret); } if (!--URCU_TLS(ust_mutex_nest)) pthread_mutex_unlock(&ust_mutex); ret = pthread_sigmask(SIG_SETMASK, &orig_mask, NULL); if (ret) { - ERR("pthread_sigmask: %s", strerror(ret)); - } - ret = pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, &oldstate); - if (ret) { - ERR("pthread_setcancelstate: %s", strerror(ret)); + ERR("pthread_sigmask: ret=%d", ret); } - if (oldstate != PTHREAD_CANCEL_DISABLE) { - ERR("pthread_setcancelstate: unexpected oldstate"); + if (lttng_ust_cancelstate_disable_pop()) { + ERR("lttng_ust_cancelstate_disable_pop"); } } @@ -259,7 +270,7 @@ struct sock_info { int statedump_pending; int initial_statedump_done; /* Keep procname for statedump */ - char procname[LTTNG_UST_ABI_PROCNAME_LEN]; + char procname[LTTNG_UST_CONTEXT_PROCNAME_LEN]; }; /* Socket from app (connect) to session daemon (listen) for communication */ @@ -482,7 +493,7 @@ int setup_global_apps(void) } global_apps.allowed = 1; - lttng_pthread_getname_np(global_apps.procname, LTTNG_UST_ABI_PROCNAME_LEN); + lttng_pthread_getname_np(global_apps.procname, LTTNG_UST_CONTEXT_PROCNAME_LEN); error: return ret; } @@ -528,7 +539,7 @@ int setup_local_apps(void) goto end; } - lttng_pthread_getname_np(local_apps.procname, LTTNG_UST_ABI_PROCNAME_LEN); + lttng_pthread_getname_np(local_apps.procname, LTTNG_UST_CONTEXT_PROCNAME_LEN); end: return ret; } @@ -1459,8 +1470,7 @@ void cleanup_sock_info(struct sock_info *sock_info, int exiting) } sock_info->root_handle = -1; } - sock_info->registration_done = 0; - sock_info->initial_statedump_done = 0; + /* * wait_shm_mmap, socket and notify socket are used by listener @@ -1472,6 +1482,9 @@ void cleanup_sock_info(struct sock_info *sock_info, int exiting) if (exiting) return; + sock_info->registration_done = 0; + sock_info->initial_statedump_done = 0; + if (sock_info->socket != -1) { ret = ustcomm_close_unix_sock(sock_info->socket); if (ret) { @@ -1744,18 +1757,25 @@ void wait_for_sessiond(struct sock_info *sock_info) DBG("Waiting for %s apps sessiond", sock_info->name); /* Wait for futex wakeup */ - if (uatomic_read((int32_t *) sock_info->wait_shm_mmap)) - goto end_wait; - - while (lttng_ust_futex_async((int32_t *) sock_info->wait_shm_mmap, - FUTEX_WAIT, 0, NULL, NULL, 0)) { + while (!uatomic_read((int32_t *) sock_info->wait_shm_mmap)) { + if (!lttng_ust_futex_async((int32_t *) sock_info->wait_shm_mmap, FUTEX_WAIT, 0, NULL, NULL, 0)) { + /* + * Prior queued wakeups queued by unrelated code + * using the same address can cause futex wait to + * return 0 even through the futex value is still + * 0 (spurious wakeups). Check the value again + * in user-space to validate whether it really + * differs from 0. + */ + continue; + } switch (errno) { - case EWOULDBLOCK: + case EAGAIN: /* Value already changed. */ goto end_wait; case EINTR: /* Retry if interrupted by signal. */ - break; /* Get out of switch. */ + break; /* Get out of switch. Check again. */ case EFAULT: wait_poll_fallback = 1; DBG( @@ -2183,7 +2203,7 @@ void lttng_ust_ctor(void) * this library so it never becomes zero, thus never gets unloaded from the * address space of the process. Since we are already running in the * constructor of the LTTNG_UST_LIB_SONAME library, calling dlopen will - * simply increment the refcount and no additionnal work is needed by the + * simply increment the refcount and no additional work is needed by the * dynamic loader as the shared library is already loaded in the address * space. As a safe guard, we use the RTLD_NODELETE flag to prevent * unloading of the UST library if its refcount becomes zero (which should @@ -2520,7 +2540,7 @@ void lttng_ust_after_fork_parent(sigset_t *restore_sigset) return; DBG("process %d", getpid()); lttng_ust_urcu_after_fork_parent(); - /* Release mutexes and reenable signals */ + /* Release mutexes and re-enable signals */ ust_after_fork_common(restore_sigset); } @@ -2547,7 +2567,7 @@ void lttng_ust_after_fork_child(sigset_t *restore_sigset) /* Release urcu mutexes */ lttng_ust_urcu_after_fork_child(); lttng_ust_cleanup(0); - /* Release mutexes and reenable signals */ + /* Release mutexes and re-enable signals */ ust_after_fork_common(restore_sigset); lttng_ust_ctor(); }