Reset all signal handlers of the child not set to SIG_IGN to SIG_DFL. Mutually exclusive with CLONE_SIGHAND to not disturb other thread's signal handler. In the spirit of closer cooperation between glibc developers and kernel developers (cf. [2]) this patchset came out of a discussion on the glibc mailing list for improving posix_spawn() (cf. [1], [3], [4]). Kernel support for this feature has been explicitly requested by glibc and I see no reason not to help them with this. The child helper process on Linux posix_spawn must ensure that no signal handlers are enabled, so the signal disposition must be either SIG_DFL or SIG_IGN. However, it requires a sigprocmask to obtain the current signal mask and at least _NSIG sigaction calls to reset the signal handlers for each posix_spawn call or complex state tracking that might lead to data corruption in glibc. Adding this flags lets glibc avoid these problems. [1]: https://www.sourceware.org/ml/libc-alpha/2019-10/msg00149.html [3]: https://www.sourceware.org/ml/libc-alpha/2019-10/msg00158.html [4]: https://www.sourceware.org/ml/libc-alpha/2019-10/msg00160.html [2]: https://lwn.net/Articles/799331/ '[...] by asking for better cooperation with the C-library projects in general. They should be copied on patches containing ABI changes, for example. I noted that there are often times where C-library developers wish the kernel community had done things differently; how could those be avoided in the future? Members of the audience suggested that more glibc developers should perhaps join the linux-api list. The other suggestion was to "copy Florian on everything".' Cc: Florian Weimer <fweimer@redhat.com> Cc: libc-alpha@sourceware.org Cc: linux-api@vger.kernel.org Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> Link: https://lore.kernel.org/r/20191014104538.3096-1-christian.brauner@ubuntu.com
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| @@ -33,6 +33,9 @@ · 32 unmodified lines | |||
| 33 | #define CLONE_NEWNET 0x40000000 /* New network namespace */ | 33 | #define CLONE_NEWNET 0x40000000 /* New network namespace */ |
| 34 | #define CLONE_IO 0x80000000 /* Clone io context */ | 34 | #define CLONE_IO 0x80000000 /* Clone io context */ |
| 35 | 35 | ||
| 36 | /* Flags for the clone3() syscall. */ | ||
| 37 | #define CLONE_CLEAR_SIGHAND 0x100000000ULL /* Clear any signal handler and reset to SIG_DFL. */ | ||
| 38 | |||
| 36 | #ifndef __ASSEMBLY__ | 39 | #ifndef __ASSEMBLY__ |
| 37 | /** | 40 | /** |
| 38 | * struct clone_args - arguments for the clone3 syscall | 41 | * struct clone_args - arguments for the clone3 syscall |