4a027d50c7
for the process, not a separate set for each thread). By default, the process now only has signal handlers installed for SIGVTALRM, SIGINFO and SIGCHLD. The thread kernel signal handler is installed for other signals on demand. This means that SIG_IGN and SIG_DFL processing is now left to the kernel, not the thread kernel. Change the signal dispatch to no longer use a signal thread, and call the signal handler using the stack of the thread that has the signal pending. Change the atomic lock method to use test-and-set asm code with a yield if blocked. This introduces separate locks for each type of object instead of blocking signals to prevent a context switch. It was this blocking of signals that caused the performance degradation the people have noted. This is a *big* change!
367 lines
9.3 KiB
C
367 lines
9.3 KiB
C
/*
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* Copyright (c) 1995 John Birrell <jb@cimlogic.com.au>.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by John Birrell.
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* 4. Neither the name of the author nor the names of any co-contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $Id: uthread_file.c,v 1.2 1998/04/11 07:47:20 jb Exp $
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*
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* POSIX stdio FILE locking functions. These assume that the locking
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* is only required at FILE structure level, not at file descriptor
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* level too.
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*
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/queue.h>
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#ifdef _THREAD_SAFE
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#include <pthread.h>
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#include "pthread_private.h"
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/*
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* Weak symbols for externally visible functions in this file:
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*/
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#pragma weak flockfile=_flockfile
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#pragma weak ftrylockfile=_ftrylockfile
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#pragma weak funlockfile=_funlockfile
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/*
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* The FILE lock structure. The FILE *fp is locked if the owner is
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* not NULL. If not locked, the file lock structure can be
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* reassigned to a different file by setting fp.
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*/
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struct file_lock {
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LIST_ENTRY(file_lock) entry; /* Entry if file list. */
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TAILQ_HEAD(lock_head, pthread)
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l_head; /* Head of queue for threads */
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/* waiting on this lock. */
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FILE *fp; /* The target file. */
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pthread_t owner; /* Thread that owns lock. */
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int count; /* Lock count for owner. */
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};
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/*
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* The number of file lock lists into which the file pointer is
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* hashed. Ideally, the FILE structure size would have been increased,
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* but this causes incompatibility, so separate data structures are
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* required.
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*/
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#define NUM_HEADS 128
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/*
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* This macro casts a file pointer to a long integer and right
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* shifts this by the number of bytes in a pointer. The shifted
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* value is then remaindered using the maximum number of hash
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* entries to produce and index into the array of static lock
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* structures. If there is a collision, a linear search of the
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* dynamic list of locks linked to each static lock is perfomed.
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*/
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#define file_idx(_p) ((((long) _p) >> sizeof(void *)) % NUM_HEADS)
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/*
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* Global array of file locks. The first lock for each hash bucket is
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* allocated statically in the hope that there won't be too many
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* collisions that require a malloc and an element added to the list.
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*/
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struct static_file_lock {
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LIST_HEAD(file_list_head, file_lock) head;
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struct file_lock fl;
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} flh[NUM_HEADS];
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/* Set to non-zero when initialisation is complete: */
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static int init_done = 0;
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/* Lock for accesses to the hash table: */
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static long hash_lock = 0;
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/*
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* Find a lock structure for a FILE, return NULL if the file is
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* not locked:
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*/
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static
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struct file_lock *
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find_lock(int idx, FILE *fp)
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{
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struct file_lock *p;
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/* Check if the file is locked using the static structure: */
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if (flh[idx].fl.fp == fp && flh[idx].fl.owner != NULL)
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/* Return a pointer to the static lock: */
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p = &flh[idx].fl;
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else {
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/* Point to the first dynamic lock: */
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p = flh[idx].head.lh_first;
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/*
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* Loop through the dynamic locks looking for the
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* target file:
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*/
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while (p != NULL && p->fp != fp && p->owner != NULL)
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/* Not this file, try the next: */
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p = p->entry.le_next;
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}
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return(p);
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}
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/*
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* Lock a file, assuming that there is no lock structure currently
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* assigned to it.
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*/
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static
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struct file_lock *
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do_lock(int idx, FILE *fp)
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{
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struct file_lock *p;
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/* Check if the static structure is not being used: */
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if (flh[idx].fl.owner == NULL) {
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/* Return a pointer to the static lock: */
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p = &flh[idx].fl;
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}
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else {
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/* Point to the first dynamic lock: */
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p = flh[idx].head.lh_first;
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/*
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* Loop through the dynamic locks looking for a
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* lock structure that is not being used:
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*/
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while (p != NULL && p->owner != NULL)
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/* This one is used, try the next: */
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p = p->entry.le_next;
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}
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/*
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* If an existing lock structure has not been found,
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* allocate memory for a new one:
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*/
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if (p == NULL && (p = (struct file_lock *)
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malloc(sizeof(struct file_lock))) != NULL) {
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/* Add the new element to the list: */
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LIST_INSERT_HEAD(&flh[idx].head, p, entry);
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}
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/* Check if there is a lock structure to acquire: */
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if (p != NULL) {
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/* Acquire the lock for the running thread: */
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p->fp = fp;
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p->owner = _thread_run;
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p->count = 1;
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TAILQ_INIT(&p->l_head);
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}
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return(p);
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}
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void
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_flockfile_debug(FILE * fp, char *fname, int lineno)
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{
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int fd, flags;
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int status;
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int idx = file_idx(fp);
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struct file_lock *p;
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/* Check if this is a real file: */
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if (fp->_file >= 0) {
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/* Lock the hash table: */
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_spinlock(&hash_lock);
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/* Check if the static array has not been initialised: */
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if (!init_done) {
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/* Initialise the global array: */
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memset(flh,0,sizeof(flh));
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/* Flag the initialisation as complete: */
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init_done = 1;
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}
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/* Get a pointer to any existing lock for the file: */
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if ((p = find_lock(idx, fp)) == NULL) {
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/*
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* The file is not locked, so this thread can
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* grab the lock:
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*/
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p = do_lock(idx, fp);
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/* Unlock the hash table: */
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_atomic_unlock(&hash_lock);
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/*
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* The file is already locked, so check if the
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* running thread is the owner:
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*/
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} else if (p->owner == _thread_run) {
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/*
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* The running thread is already the
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* owner, so increment the count of
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* the number of times it has locked
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* the file:
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*/
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p->count++;
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/* Unlock the hash table: */
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_atomic_unlock(&hash_lock);
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} else {
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/*
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* The file is locked for another thread.
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* Append this thread to the queue of
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* threads waiting on the lock.
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*/
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TAILQ_INSERT_TAIL(&p->l_head,_thread_run,qe);
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/* Unlock the hash table: */
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_atomic_unlock(&hash_lock);
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/* Wait on the FILE lock: */
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_thread_kern_sched_state(PS_FILE_WAIT, fname, lineno);
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}
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}
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return;
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}
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void
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_flockfile(FILE * fp)
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{
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_flockfile_debug(fp, __FILE__, __LINE__);
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return;
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}
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int
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_ftrylockfile(FILE * fp)
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{
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int ret = -1;
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int status;
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int idx = file_idx(fp);
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struct file_lock *p;
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/* Check if this is a real file: */
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if (fp->_file >= 0) {
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/* Lock the hash table: */
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_spinlock(&hash_lock);
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/* Get a pointer to any existing lock for the file: */
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if ((p = find_lock(idx, fp)) == NULL) {
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/*
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* The file is not locked, so this thread can
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* grab the lock:
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*/
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p = do_lock(idx, fp);
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/*
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* The file is already locked, so check if the
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* running thread is the owner:
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*/
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} else if (p->owner == _thread_run) {
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/*
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* The running thread is already the
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* owner, so increment the count of
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* the number of times it has locked
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* the file:
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*/
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p->count++;
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} else {
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/*
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* The file is locked for another thread,
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* so this try fails.
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*/
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p = NULL;
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}
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/* Check if the lock was obtained: */
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if (p != NULL)
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/* Return success: */
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ret = 0;
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/* Unlock the hash table: */
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_atomic_unlock(&hash_lock);
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}
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return (ret);
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}
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void
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_funlockfile(FILE * fp)
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{
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int status;
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int idx = file_idx(fp);
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struct file_lock *p;
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/* Check if this is a real file: */
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if (fp->_file >= 0) {
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/* Lock the hash table: */
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_spinlock(&hash_lock);
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/*
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* Get a pointer to the lock for the file and check that
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* the running thread is the one with the lock:
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*/
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if ((p = find_lock(idx, fp)) != NULL &&
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p->owner == _thread_run) {
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/*
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* Check if this thread has locked the FILE
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* more than once:
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*/
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if (p->count > 1)
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/*
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* Decrement the count of the number of
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* times the running thread has locked this
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* file:
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*/
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p->count--;
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else {
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/*
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* The running thread will release the
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* lock now:
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*/
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p->count = 0;
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/* Get the new owner of the lock: */
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if ((p->owner = TAILQ_FIRST(&p->l_head)) != NULL) {
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/* Pop the thread off the queue: */
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TAILQ_REMOVE(&p->l_head,p->owner,qe);
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/*
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* This is the first lock for the new
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* owner:
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*/
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p->count = 1;
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/* Allow the new owner to run: */
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PTHREAD_NEW_STATE(p->owner,PS_RUNNING);
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}
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}
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}
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/* Unlock the hash table: */
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_atomic_unlock(&hash_lock);
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}
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return;
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}
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#endif
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