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| author | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2019-11-13 17:45:13 -0300 |
|---|---|---|
| committer | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2019-12-19 16:11:09 -0300 |
| commit | 9b2cf9482a9397c4711c9e7f42f8d718b6306bdc (patch) | |
| tree | 2038aa8dfbc9777bb54cc7d2c15ae7e0d31965e9 /sysdeps/unix/sysv/linux/kernel-features.h | |
| parent | c5cbdacb8acec54e140c879393c8c7dd658c3488 (diff) | |
| download | glibc-9b2cf9482a9397c4711c9e7f42f8d718b6306bdc.tar.gz glibc-9b2cf9482a9397c4711c9e7f42f8d718b6306bdc.tar.xz glibc-9b2cf9482a9397c4711c9e7f42f8d718b6306bdc.zip | |
linux: Use waitid on wait4 if __NR_wait4 is not defined
If the wait4 syscall is not available (such as y2038 safe 32-bit systems) waitid should be used instead. However prior Linux 5.4 waitid is not a full superset of other wait syscalls, since it does not include support for waiting for the current process group. It is possible to emulate wait4 by issuing an extra syscall to get the current process group, but it is inherent racy: after the current process group is received and before it is passed to waitid a signal could arrive causing the current process group to change. So waitid is used if wait4 is not defined iff the build is enabled with a minimum kernel if 5.4+. The new assume __ASSUME_WAITID_PID0_P_PGID is added and an error is issued if waitid can not be implemented by either __NR_wait4 or __NR_waitid && __ASSUME_WAITID_PID0_P_PGID. Checked on x86_64-linux-gnu and i686-linux-gnu. Co-authored-by: Alistair Francis <alistair.francis@wdc.com>
Diffstat (limited to 'sysdeps/unix/sysv/linux/kernel-features.h')
| -rw-r--r-- | sysdeps/unix/sysv/linux/kernel-features.h | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/kernel-features.h b/sysdeps/unix/sysv/linux/kernel-features.h index e6be76ff46..43faaa3f9d 100644 --- a/sysdeps/unix/sysv/linux/kernel-features.h +++ b/sysdeps/unix/sysv/linux/kernel-features.h @@ -208,4 +208,10 @@ # define __ASSUME_TIME64_SYSCALLS 1 #endif +/* Linux waitid prior kernel 5.4 does not support waiting for the current + process group. */ +#if __LINUX_KERNEL_VERSION >= 0x050400 +# define __ASSUME_WAITID_PID0_P_PGID +#endif + #endif /* kernel-features.h */ |