From 982052994af40833768fef0bd342a42a1775e572 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Tue, 21 Feb 2012 12:41:18 -0500 Subject: [PATCH 1/1] fix: Only munmap the wait page when not exiting from process Signed-off-by: Mathieu Desnoyers --- liblttng-ust/lttng-ust-comm.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/liblttng-ust/lttng-ust-comm.c b/liblttng-ust/lttng-ust-comm.c index d0641c5c..dda4743f 100644 --- a/liblttng-ust/lttng-ust-comm.c +++ b/liblttng-ust/lttng-ust-comm.c @@ -383,7 +383,7 @@ error: } static -void cleanup_sock_info(struct sock_info *sock_info) +void cleanup_sock_info(struct sock_info *sock_info, int exiting) { int ret; @@ -402,7 +402,18 @@ void cleanup_sock_info(struct sock_info *sock_info) sock_info->root_handle = -1; } sock_info->constructor_sem_posted = 0; - if (sock_info->wait_shm_mmap) { + /* + * When called from process exit, we allow this memory map to be + * released by the OS at exit(), because removing it prior to + * this can cause a segmentation fault when using the + * futex_async timer-based fallback. And we cannot join those + * threads because sys_futex does not react to the cancellation + * request. + * + * So we actually _do_ release it only after a fork, since all + * threads have vanished anyway. + */ + if (!exiting && sock_info->wait_shm_mmap) { ret = munmap(sock_info->wait_shm_mmap, sysconf(_SC_PAGE_SIZE)); if (ret) { ERR("Error unmapping wait shm"); @@ -876,9 +887,9 @@ void __attribute__((constructor)) lttng_ust_init(void) static void lttng_ust_cleanup(int exiting) { - cleanup_sock_info(&global_apps); + cleanup_sock_info(&global_apps, exiting); if (local_apps.allowed) { - cleanup_sock_info(&local_apps); + cleanup_sock_info(&local_apps, exiting); } lttng_ust_abi_exit(); lttng_ust_events_exit(); @@ -923,6 +934,10 @@ void __attribute__((destructor)) lttng_ust_exit(void) ERR("Error cancelling local ust listener thread"); } } + /* + * We cannot join the threads because they might be waiting on + * sys_futex. Simply let the OS exit() clean up those threads. + */ lttng_ust_cleanup(1); } -- 2.34.1