The commit 2433d39b69, which added time64 support to select, changed
the function to use __NR_pselect6 (or __NR_pelect6_time64) on all
architectures. However, on architectures where the symbol was
implemented with __NR_select the kernel normalizes the passed timeout
instead of return EINVAL. For instance, the input timeval
{ 0, 5000000 } is interpreted as { 5, 0 }.
And as indicated by BZ #27651, this semantic seems to be expected
and changing it results in some performance issues (most likely
the program does not check the return code and keeps issuing
select with unormalized tv_usec argument).
To avoid a different semantic depending whether which syscall the
architecture used to issue, select now always normalize the timeout
input. This is a slight change for some ABIs (for instance aarch64).
Checked on x86_64-linux-gnu and i686-linux-gnu.
I used these shell commands:
../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")
and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 6694 files FOO.
I then removed trailing white space from benchtests/bench-pthread-locks.c
and iconvdata/tst-iconv-big5-hkscs-to-2ucs4.c, to work around this
diagnostic from Savannah:
remote: *** pre-commit check failed ...
remote: *** error: lines with trailing whitespace found
remote: error: hook declined to update refs/heads/master
The syscall __NR_pselect6_time64 (32-bit) or __NR_pselect6 (64-bit)
is used as default. For architectures with __ASSUME_TIME64_SYSCALLS
the 32-bit fallback uses __NR_select/__NR__newselect or __NR_pselect6
(it should cover the microblaze case where older kernels do not
provide __NR_pselect6).
Checked on x86_64-linux-gnu and i686-linux-gnu (on 5.4 and on 4.15
kernel).
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
This patch consolidates the select Linux syscall implementation on
sysdeps/unix/sysv/linux/select.c. The changes are:
1. Remove select from auto-generation syscalls.list on the architecture
that uses __NR_select.
2. Remove generic implementation add a default one that handle all
current cases (with the expection of alpha)
The new default implementation will either use __NR_select if
available of fallback to __NR_pselect6 otherwise.
3. Add a alpha outlier implementation which requires old compatibility
symbols.
Checked on i686-linux-gnu, x86_64-linux-gnu, x86_64-linux-gnux32,
arch64-linux-gnu, arm-linux-gnueabihf, and powerpc64le-linux-gnu.
* sysdeps/unix/sysv/linux/alpha/Makefile (sysdep_routines): Add
osf_select.
* sysdeps/unix/sysv/linux/alpha/select.c: New file.
* sysdeps/unix/sysv/linux/alpha/syscalls.list: Remove select and
osf_select from auto-generation list.
* sysdeps/unix/sysv/linux/syscalls.list: Likewise.
* sysdeps/unix/sysv/linux/sparc/sparc64/syscalls.list: Likewise.
* sysdeps/unix/sysv/linux/generic/select.c: Remove file.
* sysdeps/unix/sysv/linux/select.c: New file.
