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As discussed in libc-alpha [1] current clone with CLONE_VM (without CLONE_THREAD set) will reset the pthread pid/tid fields to -1. The issue is since memory is shared between the parent and child it will clobber parent's cached pid/tid leading to internal inconsistencies if the value is not restored. And even it is restored it may lead to racy conditions when between set/restore a thread might invoke pthread function that validate the pthread with INVALID_TD_P/INVALID_NOT_TERMINATED_TD_P and thus get wrong results. As stated in BZ19957, previously reports of this behaviour was close with EWONTFIX due the fact usage of clone outside glibc is tricky since glibc requires consistent internal pthread, while using clone directly may not provide it. However since now posix_spawn uses clone (CLONE_VM) to fixes various issues related to previous vfork usage this issue requires fixing. The vfork implementation also does something similar, but instead it negates and restores only the *pid* field and functions that might access its value know to handle such case (getpid, raise and pthread ones that uses INVALID_TD_P/INVALID_NOT_TERMINATED_TD_P macros that check only *tid* field). Also vfork does not call __clone directly, instead calling either __NR_vfork or __NR_clone directly. So this patch removes this clone behavior by avoiding setting the pthread pid/tid field for CLONE_VM. There is no need to check for CLONE_THREAD, since the minimum supported kernel in all architecture implies that CLONE_VM must be used with CLONE_THREAD, otherwise clone returns EINVAL. Instead of current approach of: int clone(int (*fn)(void *), void *child_stack, int flags, ...) [...] if (flags & CLONE_THREAD) goto do_syscall; pid_t new_value; if (flags & CLONE_VM) new_value = -1; else new_value = getpid (); THREAD_SETMEM (THREAD_SELF, pid, new_value); THREAD_SETMEM (THREAD_SELF, tid, new_value); do_syscall: [...] The new approach uses: int clone(int (*fn)(void *), void *child_stack, int flags, ...) [...] if (flags & CLONE_VM) goto do_syscall; pid_t new_value = getpid (); THREAD_SETMEM (THREAD_SELF, pid, new_value); THREAD_SETMEM (THREAD_SELF, tid, new_value); do_syscall: [...] It also removes the linux tst-getpid2.c test which expects the previous behavior and instead add another clone test. Tested on x86_64, i686, x32, powerpc64le, aarch64, armhf, s390, and s390x. I also did limited check on mips32 and sparc64 (using the new added test). I also got reviews from both m68k, hppa, and tile. So I presume for these architecture the patch works. The fixes for alpha, microblaze, sh, ia64, and nio2 have not been tested. [1] https://sourceware.org/ml/libc-alpha/2016-04/msg00307.html * sysdeps/unix/sysv/linux/Makefile [$(subdir) == nptl] (test): Remove tst-getpid2. (test): Add tst-clone2. * sysdeps/unix/sysv/linux/tst-clone2.c: New file. * sysdeps/unix/sysv/linux/aarch64/clone.S (__clone): Do not change pid/tid fields for CLONE_VM. * sysdeps/unix/sysv/linux/arm/clone.S: Likewise. * sysdeps/unix/sysv/linux/i386/clone.S: Likewise. * sysdeps/unix/sysv/linux/mips/clone.S: Likewise. * sysdeps/unix/sysv/linux/powerpc/powerpc32/clone.S: Likewise. * sysdeps/unix/sysv/linux/powerpc/powerpc64/clone.S: Likewise. * sysdeps/unix/sysv/linux/s390/s390-32/clone.S: Likewise. * sysdeps/unix/sysv/linux/s390/s390-64/clone.S: Likewise. * sysdeps/unix/sysv/linux/sparc/sparc32/clone.S: Likewise. * sysdeps/unix/sysv/linux/sparc/sparc64/clone.S: Likewise. * sysdeps/unix/sysv/linux/x86_64/clone.S: Likewise. * sysdeps/unix/sysv/linux/tst-getpid2.c: Remove file. |
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.. | ||
64 | ||
x32 | ||
____longjmp_chk.S | ||
__start_context.S | ||
arch-fork.h | ||
brk.c | ||
cancellation.S | ||
clone.S | ||
compat-timer.h | ||
configure | ||
configure.ac | ||
dl-cache.h | ||
dl-procinfo.c | ||
dl-procinfo.h | ||
get_clockfreq.c | ||
getcontext.S | ||
Implies | ||
init-first.c | ||
kernel_stat.h | ||
kernel-features.h | ||
ldconfig.h | ||
ldd-rewrite.sed | ||
libc-cancellation.S | ||
libc-lowlevellock.S | ||
libmvec.abilist | ||
librt-cancellation.S | ||
lll_timedlock_wait.c | ||
lll_timedwait_tid.c | ||
lowlevellock.h | ||
lowlevellock.S | ||
lowlevelrobustlock.S | ||
makecontext.c | ||
Makefile | ||
profil-counter.h | ||
pthread_cond_broadcast.S | ||
pthread_cond_signal.S | ||
pthread_cond_timedwait.S | ||
pthread_cond_wait.S | ||
pthread_setaffinity.c | ||
readelflib.c | ||
recv.c | ||
register-dump.h | ||
sched_setaffinity.c | ||
send.c | ||
setcontext.S | ||
sigaction.c | ||
sigaltstack-offsets.sym | ||
sigcontextinfo.h | ||
sigpending.c | ||
sigprocmask.c | ||
swapcontext.S | ||
syscall.S | ||
syscalls.list | ||
sysdep-cancel.h | ||
sysdep.h | ||
sysdep.S | ||
timer_create.c | ||
timer_delete.c | ||
timer_getoverr.c | ||
timer_gettime.c | ||
timer_settime.c | ||
ucontext_i.sym | ||
umount.c | ||
Versions | ||
vfork.S |