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| author | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2018-02-01 17:57:56 -0200 |
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| committer | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2018-02-22 16:43:59 -0300 |
| commit | 27761a1042daf01987e7d79636d0c41511c6df3c (patch) | |
| tree | 184aa94def7e3dcc462acfed41ee2ab5197eefbc /ChangeLog | |
| parent | 92aabad9b20be814f9dad4e7f39999605741366d (diff) | |
| download | glibc-27761a1042daf01987e7d79636d0c41511c6df3c.tar.gz glibc-27761a1042daf01987e7d79636d0c41511c6df3c.tar.xz glibc-27761a1042daf01987e7d79636d0c41511c6df3c.zip | |
Refactor atfork handlers
Current implementation (sysdeps/nptl/fork.c) replicates the atfork handlers list backward to invoke the child handlers after fork/clone syscall. The internal atfork handlers is implemented as a single-linked list so a lock-free algorithm can be used, trading fork mulithread call performance for some code complexity and dynamic stack allocation (since the backwards list should not fail). This patch refactor it to use a dynarary instead of a linked list. It simplifies the external variables need to be exported and also the internal atfork handler member definition. The downside is a serialization of fork call in multithread, since to operate on the dynarray the internal lock should be used. However as noted by Florian, it already acquires external locks for malloc and libio so it is already hitting some lock contention. Besides, posix_spawn should be faster and more scalable to run external programs in multithread environments. Checked on x86_64-linux-gnu. * nptl/Makefile (routines): Remove unregister-atfork. * nptl/register-atfork.c (fork_handler_pool): Remove variable. (fork_handler_alloc): Remove function. (fork_handlers, fork_handler_init): New variables. (__fork_lock): Rename to atfork_lock. (__register_atfork, __unregister_atfork, libc_freeres_fn): Rewrite to use a dynamic array to add/remove atfork handlers. * sysdeps/nptl/fork.c (__libc_fork): Likewise. * sysdeps/nptl/fork.h (__fork_lock, __fork_handlers, __linkin_atfork): Remove declaration. (fork_handler): Remove next, refcntr, and need_signal member. (__run_fork_handler_type): New enum. (__run_fork_handlers): New prototype. * sysdeps/nptl/libc-lockP.h (__libc_atfork): Remove declaration.
Diffstat (limited to 'ChangeLog')
| -rw-r--r-- | ChangeLog | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/ChangeLog b/ChangeLog index 059537497c..b8e3f8d091 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,5 +1,21 @@ 2018-02-22 Adhemerval Zanella <adhemerval.zanella@linaro.org> + * nptl/Makefile (routines): Remove unregister-atfork. + * nptl/register-atfork.c (fork_handler_pool): Remove variable. + (fork_handler_alloc): Remove function. + (fork_handlers, fork_handler_init): New variables. + (__fork_lock): Rename to atfork_lock. + (__register_atfork, __unregister_atfork, libc_freeres_fn): Rewrite + to use a dynamic array to add/remove atfork handlers. + * sysdeps/nptl/fork.c (__libc_fork): Likewise. + * sysdeps/nptl/fork.h (__fork_lock, __fork_handlers, __linkin_atfork): + Remove declaration. + (fork_handler): Remove next, refcntr, and need_signal member. + (__run_fork_handler_type): New enum. + (__run_fork_handlers): New prototype. + * nptl/register-atfork.c: Remove file. + * sysdeps/nptl/libc-lockP.h (__libc_atfork): Remove declaration. + * sysdeps/nptl/nptl-signals.h: Move to ... * sysdeps/generic/internal-signals.h: ... here. Adjust internal comments. |