Current GLIBC has two ways to implement the single thread optimization
on syscalls to avoid calling the cancellation path: either by using
global variables (__{libc,pthread}_multiple_thread) or by accessing
the TCB field (defined by TLS_MULTIPLE_THREADS_IN_TCB). Both the
variables and the macros to acces its value are defined in the
architecture sysdep-cancel.h header.
This patch consolidates its definition on only one header,
sysdeps/unix/sysv/linux/sysdep-cancel.h, and adds a new define
(SINGLE_THREAD_BY_GLOBAL) which the architecture defines if it prefer
to use the global variables instead of the TCB field. This is an
optimization, so if the architecture does not define it, the TCB
method will be used as default.
Checked on x86_64-linux-gnu and on a build with major touched
ABIs (aarch64-linux-gnu, alpha-linux-gnu, arm-linux-gnueabihf,
hppa-linux-gnu, i686-linux-gnu, m68k-linux-gnu, microblaze-linux-gnu,
mips-linux-gnu, mips64-linux-gnu, powerpc-linux-gnu,
powerpc64le-linux-gnu, s390-linux-gnu, s390x-linux-gnu, sh4-linux-gnu,
sparcv9-linux-gnu, sparc64-linux-gnu, tilegx-linux-gnu).
* sysdeps/unix/sysv/linux/aarch64/sysdep-cancel.h: Remove file.
* sysdeps/unix/sysv/linux/alpha/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/arm/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/hppa/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/mips/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/nios2/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/powerpc/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-32/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-64/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/sh/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/sparc/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/tile/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/x86_64/sysdep-cancel.h: Likewise.
* sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
(SINGLE_THREAD_BY_GLOBAL): Define.
* sysdeps/unix/sysv/linux/aarch64/sysdep.h (SINGLE_THREAD_BY_GLOBAL):
Likewise.
* sysdeps/unix/sysv/linux/alpha/sysdep.h (SINGLE_THREAD_BY_GLOBAL):
Likewise.
* sysdeps/unix/sysv/linux/arm/sysdep.h (SINGLE_THREAD_BY_GLOBAL):
Likewise.
* sysdeps/unix/sysv/linux/hppa/sysdep.h (SINGLE_THREAD_BY_GLOBAL):
Likewise.
* sysdeps/unix/sysv/linux/microblaze/sysdep.h
(SINGLE_THREAD_BY_GLOBAL): Likewise.
* sysdeps/unix/sysv/linux/x86_64/sysdep.h (SINGLE_THREAD_BY_GLOBAL):
Likewise.
If a function passes in a variable named "ret", the code will miscompile
when it declares a local ret variable. In some cases, it's even a build
failure like so:
../sysdeps/unix/sysv/linux/spawni.c: In function '__spawni_child':
../sysdeps/unix/sysv/linux/spawni.c:289:5: error: address of register variable 'ret' requested
while (write_not_cancel (p, &ret, sizeof ret) < 0)
The semi-recent SYSCALL_CANCEL inclusion broke microblaze due to the
sysdep.h header not including the unix/sysdep.h header. Include it
here like all other ports.