This protects against a race with an upcall in the parent during the
fork which can clobber the parent's tcb before the vm space is copied
in the child. The child then gets a corrupted tcb that is either null
or that points to another thread that doesn't exist in the child (after
a fork, only the fork()ing thread exists in the child).
Reported by: Arno J. Klaassen (arno at heho / snv / jussieu / fr)
is also implemented in glibc and is used by a number of existing
applications (mysql, firefox, etc).
This mutex type is a default mutex with the additional property that
it spins briefly when attempting to acquire a contested lock, doing
trylock operations in userland before entering the kernel to block if
eventually unsuccessful.
The expectation is that applications requesting this mutex type know
that the mutex is likely to be only held for very brief periods, so it
is faster to spin in userland and probably succeed in acquiring the
mutex, than to enter the kernel and sleep, only to be woken up almost
immediately. This can help significantly in certain cases when
pthread mutexes are heavily contended and held for brief durations
(such as mysql).
Spin up to 200 times before entering the kernel, which represents only
a few us on modern CPUs. No performance degradation was observed with
this value and it is sufficient to avoid a large performance drop in
mysql performance in the heavily contended pthread mutex case.
The libkse implementation is a NOP.
Reviewed by: jeff
MFC after: 3 days
Warning, after symbol versioning is enabled, going back is not easy
(use WITHOUT_SYMVER at your own risk).
Change the default thread library to libthr.
There most likely still needs to be a version bump for at least the
thread libraries. If necessary, this will happen later.
child thread goes back to system scope rather than process
scope. This allows an ensuing exec() to actually work.
This change was made a year ago here, but I "forgot" to
commit it :(
Approved by: deischen
MFC after: 3 weeks
they become candidates for reuse. Without this fix, some of the
state from a thread structure's previous incarnation could interfere
with its new one. Specifically, a non-bound thread started as
"suspended" (see pthread_attr_setcreatesuspend_np()) might not get
scheduled at all when resumed, as the "active" flag would be set
spuriously.
Reviewed by: deischen@, davidxu@
MFC after: 1 week
is also returned by pthread_detach() if a thread was already
detached, the error code was already documented:
> [EINVAL] The implementation has detected that the value speci-
> fied by thread does not refer to a joinable thread.
do its work for SIGINFO. Always install libpthread signal handler
wrapper for SIGINFO even if user SIG_IGN's or SIG_DFL's it.
SIGINFO has a special meaning for libpthread: when LIBPTHREAD_DEBUG
enviroment variable defined it is used for dumping an information
about threads to /tmp/.
Reported by: mi
Reviewed by: deischen
MFC after: 2 weeks
used LIBTHREAD_1_0 as its version definition, but now needs
to define its symbols in the same namespace used by libc.
The compatibility hooks allows you to use libraries and
binaries built and linked to libpthread before libc was
built with symbol versioning. The shims can be removed if
libpthread is given a version bump.
Reviewed by: davidxu
* Add posix_memalign().
* Move calloc() from calloc.c to malloc.c. Add a calloc() implementation in
rtld-elf in order to make the loader happy (even though calloc() isn't
used in rtld-elf).
* Add _malloc_prefork() and _malloc_postfork(), and use them instead of
directly manipulating __malloc_lock.
Approved by: phk, markm (mentor)
functions in the child after a fork() from a threaded process,
use __sys_setprocmask() rather than setprocmask() to keep our
signal handling sane. Without this fix, signals are essentially
ignored in said child and things such as protection violations
result in an endless busy loop.
Reviewed by: deischen
o Don't reinitialise the atfork() handler list in the child. We
are meant to call the child handler, and on subsequent fork()s
should call all three functions as normal.
o Don't reinitialise the thread specific keyed data in the
child after a fork. Applications may require this for context.
o Reinitialise curthread->tlflags after removing ourselves from
(and reinitialising) the various internal thread lists.
o Reinitialise __malloc_lock in the child after fork() (to balance
our explicitly taking the lock prior to the fork()).
With these changes, it is possible to enable the NOTYET code in
thr_kern.c to allow the use of non-async-safe functions after
fork()ing from a threaded program.
Reviewed by: Daniel Eischen <deischen@freebsd.org>
[_malloc_lock reinitialisation has since been moved to avoid polluting the
!NOTYET code]
changed to use the statclock. Make sure we calculate the value
of a tick correctly in userland.
Noticed by: Kazuaki Oda <kaakun at highway dot ne dot jp>
signals instead of having more intricate knowledge of thread state
within signal handling.
Simplify signal code because of above (by David Xu).
Use macros for libpthread usage of pthread_cleanup_push() and
pthread_cleanup_pop(). This removes some instances of malloc()
and free() from the semaphore and pthread_once() implementations.
When single threaded and forking(), make sure that the current
thread's signal mask is inherited by the forked thread.
Use private mutexes for libc and libpthread. Signals are
deferred while threads hold private mutexes. This fix also
breaks www/linuxpluginwrapper; a patch that fixes it is at
http://people.freebsd.org/~deischen/kse/linuxpluginwrapper.diff
Fix race condition in condition variables where handling a
signal (pthread_kill() or kill()) may not see a wakeup
(pthread_cond_signal() or pthread_cond_broadcast()).
In collaboration with: davidxu
packages expect and seems to be most correct according to the slightly-
ambiguous standards.
MFC after: 1 month
Corroborated by: POSIX <http://tinyurl.com/4uvub>
Reviewed by: silence on threads@
