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
- Don't pollute the namespace by including <sys/types.h>, <sys/time.h>,
<sys/signal.h> and <limits.h>. Use __MINSIGSTKSZ and __ULONG_MAX from
<machine/_limits.h>, __sigset_t from <sys/_sigset.h> instead.
- Include <time.h> because POSIX says we have to.
PTHREAD_{DESTRUCTOR_ITERATIONS,KEYS_MAX,STACK_MIN,THREADS_MAX} should
eventually move to <limits.h> but are left here for now.
Discussed on: standards@, threads@
libthr. No changes were made to libpthread by request of deischen,
who will soon commit a real implementation for that library.
PR: standards/50848
Submitted by: Sergey A. Osokin <osa@freebsd.org.ru>
MFC after: 1 week
routines, remove their declarations. Even though rwlocks have the same
functions, XBDft does not shade those declarations so I am leaving them in.
(This is probably a bug in the Standard.)
# This appears to not break X11, but I'm having problems compiling the
# glide part of the server with or without this patch, so I can't tell
# for sure.
be malloc()ed, but they are now allocated using mmap(), just as the
default-size stacks are. A separate cache of stacks is kept for
non-default-size stacks.
Collaboration with: deischen
1003.1c-1995.
Undefine _POSIX_THREAD_SAFE_FUNCTIONS, since we do not implement all of the
necessary interfaces. At least getgrgid_r(), getrnam_r(), getpwuid_r(),
getpwnam_r(), getc_unlocked(), getchar_unlocked(), putc_unlocked(),
and putchar_unlocked() are missing. Due to a likely typo in 1003.1c-1995,
we are not technically allowed to define _POSIX_THREADS without defining
_POSIX_THREAD_SAFE_FUNCTIONS, but either way we're non-compliant, so I'm
leaving _POSIX_THREADS defined.
PR: bin/8281
eischen (Daniel Eischen) added wrappers to protect against cancled
threads orphaning internal resources.
the cancelability code is still a bit fuzzy but works for test
programs of my own, OpenBSD's and some examples from ORA's books.
add readdir_r to both libc and libc_r
add some 'const' attributes to function parameters
Reviewed by: eischen, jasone
not currently supported. Also corrected the declaration for
pthread_testcancel which incorrectly returned int when POSIX and
SUSv2 both say it should be void.
Submitted by: Ralf S. Engelschall <rse@engelschall.com>
Reviewed by: John Birrell <jb@freebsd.org>
implementation requires two things:
1.) The priority queues must be protected during insertion
and removal of threads. Since the kernel scheduler
must modify the priority queues, a spinlock for
protection cannot be used. The functions
_thread_kern_sched_defer() and _thread_kern_sched_undefer()
were added to {un}defer kernel scheduler activation.
2.) A thread (active) priority change can be performed only
when the thread is removed from the priority queue. The
implementation uses a threads active priority when
inserting it into the queue.
A by-product is that thread switches are much faster. A
separate queue is used for waiting and/or blocked threads,
and it is searched at most 2 times in the kernel scheduler
when there are active threads. It should be possible to
reduce this to once by combining polling of threads waiting
on I/O with the loop that looks for timed out threads and
the minimum timeout value.
o Functions to defer kernel scheduler activation were added. These
are _thread_kern_sched_defer() and _thread_kern_sched_undefer()
and may be called recursively. These routines do not block the
scheduling signal, but latch its occurrence. The signal handler
will not call the kernel scheduler when the running thread has
deferred scheduling, but it will be called when running thread
undefers scheduling.
o Added support for _POSIX_THREAD_PRIORITY_SCHEDULING. All the
POSIX routines required by this should now be implemented.
One note, SCHED_OTHER, SCHED_FIFO, and SCHED_RR are required
to be defined by including pthread.h. These defines are currently
in sched.h. I modified pthread.h to include sched.h but don't
know if this is the proper thing to do.
o Added support for priority protection and inheritence mutexes.
This allows definition of _POSIX_THREAD_PRIO_PROTECT and
_POSIX_THREAD_PRIO_INHERIT.
o Added additional error checks required by POSIX for mutexes and
condition variables.
o Provided a wrapper for sigpending which is marked as a hidden
syscall.
o Added a non-portable function as a debugging aid to allow an
application to monitor thread context switches. An application
can install a routine that gets called everytime a thread
(explicitly created by the application) gets context switched.
The routine gets passed the pthread IDs of the threads that are
being switched in and out. I found this useful, but we can
get rid of it if you want.
Submitted by: Dan Eischen <eischen@vigrid.com>
we use it in the uthreads implementation.
Moved enum pthread_mutextype here from libc_r/uthread/pthread_private.h.
Change prototype for pthread_getspecific().
Here are the diffs for libc_r to get it one step closer to P1003.1c
These make most of the thread/mutex/condvar structures opaque to the
user. There are three functions which have been renamed with _np
suffixes because they are extensions to P1003.1c (I did them for JAVA,
which needs to suspend/resume threads and also start threads suspended).
I've created a new header (pthread_np.h) for the non-POSIX stuff.
The egrep tags stuff in /usr/src/lib/libc_r/Makefile that I uncommented
doesn't work. I think its best to delete it. I don't think libc_r needs
tags anyway, 'cause most of the source is in libc which does have tags.
also:
Here's the first batch of man pages for the thread functions.
The diff to /usr/src/lib/libc_r/Makefile removes some stuff that was
inherited from /usr/src/lib/libc/Makefile that should only be done with
libc.
also:
I should have sent this diff with the pthread(3) man page.
It allows people to type
make -DWANT_LIBC_R world
to get libc_r built with the rest of the world. I put this in the
pthread(3) man page. The default is still not to build libc_r.
also:
The diff attached adds a pthread(3) man page to /usr/src/share/man/man3.
The idea is that without libc_r installed, this man page will give people
enough info to know that they have to build libc_r.
