>When this happpens, is the process holding a single (or very few) shm file references, or references to many shm files ? It is holding "all" of shm files' reference , neither a single one nor some few ones. In fact, yesterday, I tried to fix it as the following and it seems work. --- a/lttng-ust/libringbuffer/shm.c +++ b/lttng-ust/libringbuffer/shm.c @@ -32,7 +32,6 @@ #include #include #include - /* * Ensure we have the required amount of space available by writing 0 * into the entire buffer. Not doing so can trigger SIGBUS when going @@ -122,6 +121,12 @@ struct shm_object *_shm_object_table_alloc_shm(struct shm_object_table *table, /* create shm */ shmfd = stream_fd; + if (shmfd >= 0) { + ret = fcntl(shmfd, F_SETFD, FD_CLOEXEC); + if (ret < 0) { + PERROR("fcntl shmfd FD_CLOEXEC"); + } + } ret = zero_file(shmfd, memory_map_size); if (ret) { PERROR("zero_file"); @@ -272,15 +277,22 @@ struct shm_object *shm_object_table_append_shm(struct shm_object_table *table, obj->shm_fd = shm_fd; obj->shm_fd_ownership = 1; + if (shm_fd >= 0) { + ret = fcntl(shm_fd, F_SETFD, FD_CLOEXEC); + if (ret < 0) { + PERROR("fcntl shmfd FD_CLOEXEC"); + //goto error_fcntl; + } + } ret = fcntl(obj->wait_fd[1], F_SETFD, FD_CLOEXEC); if (ret < 0) { As it shows, wait_fd[1] has been set FD_CLOEXEC by fcntl() but not shm_fd. Why your patch do with wait_fd but not shm_fd? As far as I know, wait_fd is just a pipe and it seems not related to shm resource. ------------------------------------------------------------------ 发件人：Mathieu Desnoyers 发送时间：2022年3月10日(星期四) 00:46 收件人：zhenyu.ren 抄　送：Jonathan Rajotte ; lttng-dev 主　题：Re: 回复：[lttng-dev] 回复： 回复： 回复： shm leak in traced application? When this happpens, is the process holding a single (or very few) shm file references, or references to many shm files ? I wonder if you end up in a scenario where an application very frequently performs exec(), and therefore sometimes the exec() will happen in the window between the unix socket file descriptor reception and call to fcntl FD_CLOEXEC. Thanks, Mathieu ----- On Mar 8, 2022, at 8:29 PM, zhenyu.ren wrote: Thanks a lot for reply. I do not reply it in bug tracker since I have not gotten a reliable way to reproduce the leak case. ------------------------------------------------------------------ 发件人：Mathieu Desnoyers 发送时间：2022年3月8日(星期二) 23:26 收件人：zhenyu.ren 抄　送：Jonathan Rajotte ; lttng-dev 主　题：Re: [lttng-dev] 回复： 回复： 回复： shm leak in traced application? ----- On Mar 8, 2022, at 12:18 AM, lttng-dev lttng-dev@lists.lttng.org wrote: > Hi, > In shm_object_table_append_shm()/alloc_shm()， why not calling FD_CLOEXEC fcntl() > to shmfds? I guess this omission leads to shm fds leak. Those file descriptors are created when received by ustcomm_recv_fds_unix_sock, and immediately after creation they are set as FD_CLOEXEC. We should continue this discussion in the bug tracker as suggested by Jonathan. It would greatly help if you can provide a small reproducer. Thanks, Mathieu > Thanks > zhenyu.ren >> ------------------------------------------------------------------ >> 发件人：Jonathan Rajotte-Julien >> 发送时间：2022年2月25日(星期五) 22:31 >> 收件人：zhenyu.ren >> 抄 送：lttng-dev >> 主 题：Re: [lttng-dev] 回复： 回复： shm leak in traced application? >> Hi zhenyu.ren, >> Please open a bug on our bug tracker and provide a reproducer against the latest >> stable version (2.13.x). >> https://bugs.lttng.org/ >> Please follow the guidelines: https://bugs.lttng.org/#Bug-reporting-guidelines >> Cheers >> On Fri, Feb 25, 2022 at 12:47:34PM +0800, zhenyu.ren via lttng-dev wrote: >> > Hi, lttng-dev team >>> When lttng-sessiond exits, the ust applications should call >>> lttng_ust_objd_table_owner_cleanup() and clean up all shm resource(unmap and >>> close). Howerver I do find that the ust applications keep opening "all" of the >> > shm fds("/dev/shm/ust-shm-consumer-81132 (deleted)") and do NOT free shm. >>> If we run lttng-sessiond again, ust applications can get a new piece of shm and >>> a new list of shm fds so double shm usages. Then if we kill lttng-sessiond, >>> what the mostlikely happened is ust applications close the new list of shm fds >>> and free new shm resource but keeping old shm still. In other word, we can not >> > free this piece of shm unless we killing ust applications!!! >>> So Is there any possilbe that ust applications failed calling >>> lttng_ust_objd_table_owner_cleanup()? Do you have ever see this problem? Do you >>> have any advice to free the shm without killling ust applications(I tried to >> > dig into kernel shm_open and /dev/shm, but not found any ideas)? >> > Thanks in advance >> > zhenyu.ren >> > ------------------------------------------------------------------ >> > 发件人：zhenyu.ren via lttng-dev >> > 发送时间：2022年2月23日(星期三) 23:09 >> > 收件人：lttng-dev >> > 主 题：[lttng-dev] 回复： shm leak in traced application? >>> >"I found these items also exist in a traced application which is a long-time >> > >running daemon" >> > Even if lttng-sessiond has been killed!! >> > Thanks >> > zhenyu.ren >> > ------------------------------------------------------------------ >> > 发件人：zhenyu.ren via lttng-dev >> > 发送时间：2022年2月23日(星期三) 22:44 >> > 收件人：lttng-dev >> > 主 题：[lttng-dev] shm leak in traced application? >> > Hi, >>> There are many items such as "/dev/shm/ust-shm-consumer-81132 (deleted)" exist >>> in lttng-sessiond fd spaces. I know it is the result of shm_open() and >> > shm_unlnik() in create_posix_shm(). >>> However, today, I found these items also exist in a traced application which is >>> a long-time running daemon. The most important thing I found is that there >> > seems no reliable way to release share memory. >>> I tried to kill lttng-sessiond but not always release share memory. Sometimes I >>> need to kill the traced application to free share memory....But it is not a >> > good idea to kill these applications. >> > My questions are: >>> 1. Is there any way to release share memory without killing any traced >> > application? >>> 2. Is it normal that many items such as "/dev/shm/ust-shm-consumer-81132 >> > (deleted)" exist in the traced application? >> > Thanks >> > zhenyu.ren >> > _______________________________________________ >> > lttng-dev mailing list >> > lttng-dev@lists.lttng.org >> > https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev >> -- >> Jonathan Rajotte-Julien >> EfficiOS > _______________________________________________ > lttng-dev mailing list > lttng-dev@lists.lttng.org > https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com