freebsd-dev/lib/libc_r/uthread/uthread_gc.c
Daniel Eischen fbeb36e4bf Implement zero system call thread switching. Performance of
thread switches should be on par with that under scheduler
activations.

  o Timing is achieved through the use of a fixed interval
    timer (ITIMER_PROF) to count scheduling ticks instead
    of retrieving the time-of-day upon every thread switch
    and calculating elapsed real time.

  o Polling for I/O readiness is performed once for each
    scheduling tick instead of every thread switch.

  o The non-signal saving/restoring versions of setjmp/longjmp
    are used to save and restore thread contexts.  This may
    allow the removal of _THREAD_SAFE macros from setjmp()
    and longjmp() - needs more investigation.

Change signal handling so that signals are handled in the
context of the thread that is receiving the signal.  When
signals are dispatched to a thread, a special signal handling
frame is created on top of the target threads stack.  The
frame contains the threads saved state information and a new
context in which the thread can run.  The applications signal
handler is invoked through a wrapper routine that knows how
to restore the threads saved state and unwind to previous
frames.

Fix interruption of threads due to signals.  Some states
were being improperly interrupted while other states were
not being interrupted.  This should fix several PRs.

Signal handlers, which are invoked as a result of a process
signal (not by pthread_kill()), are now called with the
code (or siginfo_t if SA_SIGINFO was set in sa_flags) and
sigcontext_t as received from the process signal handler.

Modify the search for a thread to which a signal is delivered.
The search algorithm is now:

  o First thread found in sigwait() with signal in wait mask.
  o First thread found sigsuspend()'d on the signal.
  o Current thread if signal is unmasked.
  o First thread found with signal unmasked.

Collapse machine dependent support into macros defined in
pthread_private.h.  These should probably eventually be moved
into separate MD files.

Change the range of settable priorities to be compliant with
POSIX (0-31).  The threads library uses higher priorities
internally for real-time threads (not yet implemented) and
threads executing signal handlers.  Real-time threads and
threads running signal handlers add 64 and 32, respectively,
to a threads base priority.

Some other small changes and cleanups.

PR:		17757 18559 21943
Reviewed by:	jasone
2000-10-13 22:12:32 +00:00

257 lines
7.0 KiB
C

/*
* Copyright (c) 1998 John Birrell <jb@cimlogic.com.au>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by John Birrell.
* 4. Neither the name of the author nor the names of any co-contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*
* Garbage collector thread. Frees memory allocated for dead threads.
*
*/
#include <errno.h>
#include <time.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <pthread.h>
#include "pthread_private.h"
pthread_addr_t
_thread_gc(pthread_addr_t arg)
{
int f_debug;
int f_done = 0;
int ret;
sigset_t mask;
pthread_t pthread;
pthread_t pthread_cln;
struct timespec abstime;
void *p_stack;
/* Block all signals */
sigfillset(&mask);
pthread_sigmask(SIG_BLOCK, &mask, NULL);
/* Mark this thread as a library thread (not a user thread). */
_thread_run->flags |= PTHREAD_FLAGS_PRIVATE;
/* Set a debug flag based on an environment variable. */
f_debug = (getenv("LIBC_R_DEBUG") != NULL);
/* Set the name of this thread. */
pthread_set_name_np(_thread_run,"GC");
while (!f_done) {
/* Check if debugging this application. */
if (f_debug)
/* Dump thread info to file. */
_thread_dump_info();
/*
* Defer signals to protect the scheduling queues from
* access by the signal handler:
*/
_thread_kern_sig_defer();
/* Check if this is the last running thread: */
if (TAILQ_FIRST(&_thread_list) == _thread_run &&
TAILQ_NEXT(_thread_run, tle) == NULL)
/*
* This is the last thread, so it can exit
* now.
*/
f_done = 1;
/*
* Undefer and handle pending signals, yielding if
* necessary:
*/
_thread_kern_sig_undefer();
/*
* Lock the garbage collector mutex which ensures that
* this thread sees another thread exit:
*/
if (pthread_mutex_lock(&_gc_mutex) != 0)
PANIC("Cannot lock gc mutex");
/* No stack of thread structure to free yet: */
p_stack = NULL;
pthread_cln = NULL;
/*
* Enter a loop to search for the first dead thread that
* has memory to free.
*/
for (pthread = TAILQ_FIRST(&_dead_list);
p_stack == NULL && pthread_cln == NULL && pthread != NULL;
pthread = TAILQ_NEXT(pthread, dle)) {
/* Check if the initial thread: */
if (pthread == _thread_initial) {
/* Don't destroy the initial thread. */
}
/*
* Check if this thread has detached:
*/
else if ((pthread->attr.flags &
PTHREAD_DETACHED) != 0) {
/* Remove this thread from the dead list: */
TAILQ_REMOVE(&_dead_list, pthread, dle);
/*
* Check if the stack was not specified by
* the caller to pthread_create and has not
* been destroyed yet:
*/
if (pthread->attr.stackaddr_attr == NULL &&
pthread->stack != NULL) {
if (pthread->attr.stacksize_attr
== PTHREAD_STACK_DEFAULT) {
/*
* Default-size stack. Cache
* it:
*/
struct stack *spare_stack;
spare_stack
= (pthread->stack
+ PTHREAD_STACK_DEFAULT
- sizeof(struct stack));
SLIST_INSERT_HEAD(&_stackq,
spare_stack,
qe);
} else {
/*
* Non-standard stack size.
* free() it outside the locks.
*/
p_stack = pthread->stack;
}
}
/*
* Point to the thread structure that must
* be freed outside the locks:
*/
pthread_cln = pthread;
} else {
/*
* This thread has not detached, so do
* not destroy it.
*
* Check if the stack was not specified by
* the caller to pthread_create and has not
* been destroyed yet:
*/
if (pthread->attr.stackaddr_attr == NULL &&
pthread->stack != NULL) {
if (pthread->attr.stacksize_attr
== PTHREAD_STACK_DEFAULT) {
/*
* Default-size stack. Cache
* it:
*/
struct stack *spare_stack;
spare_stack
= (pthread->stack
+ PTHREAD_STACK_DEFAULT
- sizeof(struct stack));
SLIST_INSERT_HEAD(&_stackq,
spare_stack,
qe);
} else {
/*
* Non-standard stack size.
* free() it outside the locks:
*/
p_stack = pthread->stack;
}
/*
* NULL the stack pointer now
* that the memory has been freed:
*/
pthread->stack = NULL;
}
}
}
/*
* Check if this is not the last thread and there is no
* memory to free this time around.
*/
if (!f_done && p_stack == NULL && pthread_cln == NULL) {
/* Get the current time. */
if (clock_gettime(CLOCK_REALTIME,&abstime) != 0)
PANIC("gc cannot get time");
/*
* Do a backup poll in 10 seconds if no threads
* die before then.
*/
abstime.tv_sec += 10;
/*
* Wait for a signal from a dying thread or a
* timeout (for a backup poll).
*/
if ((ret = pthread_cond_timedwait(&_gc_cond,
&_gc_mutex, &abstime)) != 0 && ret != ETIMEDOUT)
PANIC("gc cannot wait for a signal");
}
/* Unlock the garbage collector mutex: */
if (pthread_mutex_unlock(&_gc_mutex) != 0)
PANIC("Cannot unlock gc mutex");
/*
* If there is memory to free, do it now. The call to
* free() might block, so this must be done outside the
* locks.
*/
if (p_stack != NULL)
free(p_stack);
if (pthread_cln != NULL)
if (pthread_cln->name != NULL) {
/* Free the thread name string. */
free(pthread_cln->name);
}
/*
* Free the memory allocated for the thread
* structure.
*/
free(pthread_cln);
}
return (NULL);
}