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gcc/boehm-gc/linux_threads.c
Tom Tromey 5a2586cf8f Makefile.am, [...]: Imported GC 6.0 and merged local changes. 
* Makefile.am, acinclude.m4, configure.in: Imported GC 6.0 and
	merged local changes.

From-SVN: r44994
2001-08-18 01:04:43 +00:00

1697 lines
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/*
* Copyright (c) 1994 by Xerox Corporation. All rights reserved.
* Copyright (c) 1996 by Silicon Graphics. All rights reserved.
* Copyright (c) 1998 by Fergus Henderson. All rights reserved.
* Copyright (c) 2000-2001 by Hewlett-Packard Company. All rights reserved.
*
* THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
* OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
*
* Permission is hereby granted to use or copy this program
* for any purpose, provided the above notices are retained on all copies.
* Permission to modify the code and to distribute modified code is granted,
* provided the above notices are retained, and a notice that the code was
* modified is included with the above copyright notice.
*/
/*
* Support code for LinuxThreads, the clone()-based kernel
* thread package for Linux which is included in libc6.
*
* This code relies on implementation details of LinuxThreads,
* (i.e. properties not guaranteed by the Pthread standard),
* though this version now does less of that than the other Pthreads
* support code.
*
* Note that there is a lot of code duplication between linux_threads.c
* and thread support for some of the other Posix platforms; any changes
* made here may need to be reflected there too.
*/
/*
* Linux_threads.c now also includes some code to support HPUX and
* OSF1 (Compaq Tru64 Unix, really). The OSF1 support is not yet
* functional. The OSF1 code is based on Eric Benson's
* patch, though that was originally against hpux_irix_threads. The code
* here is completely untested. With 0.0000001% probability, it might
* actually work.
*
* Eric also suggested an alternate basis for a lock implementation in
* his code:
* + #elif defined(OSF1)
* + unsigned long GC_allocate_lock = 0;
* + msemaphore GC_allocate_semaphore;
* + # define GC_TRY_LOCK() \
* + ((msem_lock(&GC_allocate_semaphore, MSEM_IF_NOWAIT) == 0) \
* + ? (GC_allocate_lock = 1) \
* + : 0)
* + # define GC_LOCK_TAKEN GC_allocate_lock
*/
/* #define DEBUG_THREADS 1 */
/* ANSI C requires that a compilation unit contains something */
# if defined(GC_LINUX_THREADS) || defined(LINUX_THREADS) \
|| defined(GC_HPUX_THREADS) || defined(HPUX_THREADS) \
|| defined(GC_OSF1_THREADS) || defined(OSF1_THREADS) \
# include "private/gc_priv.h"
# if defined(HPUX_THREADS) && !defined(USE_PTHREAD_SPECIFIC) \
&& !defined(USE_HPUX_TLS)
# define USE_HPUX_TLS
# endif
# ifdef THREAD_LOCAL_ALLOC
# if !defined(USE_PTHREAD_SPECIFIC) && !defined(USE_HPUX_TLS)
# include "private/specific.h"
# endif
# if defined(USE_PTHREAD_SPECIFIC)
# define GC_getspecific pthread_getspecific
# define GC_setspecific pthread_setspecific
# define GC_key_create pthread_key_create
typedef pthread_key_t GC_key_t;
# endif
# if defined(USE_HPUX_TLS)
# define GC_getspecific(x) (x)
# define GC_setspecific(key, v) ((key) = (v), 0)
# define GC_key_create(key, d) 0
typedef void * GC_key_t;
# endif
# endif
# include <stdlib.h>
# include <pthread.h>
# include <sched.h>
# include <time.h>
# include <errno.h>
# include <unistd.h>
# include <sys/mman.h>
# include <sys/time.h>
# include <semaphore.h>
# include <signal.h>
# include <sys/types.h>
# include <sys/stat.h>
# include <fcntl.h>
#ifndef __GNUC__
# define __inline__
#endif
#ifdef GC_USE_LD_WRAP
# define WRAP_FUNC(f) __wrap_##f
# define REAL_FUNC(f) __real_##f
#else
# define WRAP_FUNC(f) GC_##f
# define REAL_FUNC(f) f
# undef pthread_create
# undef pthread_sigmask
# undef pthread_join
# undef pthread_detach
#endif
void GC_thr_init();
#if 0
void GC_print_sig_mask()
{
sigset_t blocked;
int i;
if (pthread_sigmask(SIG_BLOCK, NULL, &blocked) != 0)
ABORT("pthread_sigmask");
GC_printf0("Blocked: ");
for (i = 1; i <= MAXSIG; i++) {
if (sigismember(&blocked, i)) { GC_printf1("%ld ",(long) i); }
}
GC_printf0("\n");
}
#endif
/* We use the allocation lock to protect thread-related data structures. */
/* The set of all known threads. We intercept thread creation and */
/* joins. */
/* Protected by allocation/GC lock. */
/* Some of this should be declared volatile, but that's inconsistent */
/* with some library routine declarations. */
typedef struct GC_Thread_Rep {
struct GC_Thread_Rep * next; /* More recently allocated threads */
/* with a given pthread id come */
/* first. (All but the first are */
/* guaranteed to be dead, but we may */
/* not yet have registered the join.) */
pthread_t id;
short flags;
# define FINISHED 1 /* Thread has exited. */
# define DETACHED 2 /* Thread is intended to be detached. */
# define MAIN_THREAD 4 /* True for the original thread only. */
short thread_blocked; /* Protected by GC lock. */
/* Treated as a boolean value. If set, */
/* thread will acquire GC lock before */
/* doing any pointer manipulations, and */
/* has set its sp value. Thus it does */
/* not need to be sent a signal to stop */
/* it. */
ptr_t stack_end; /* Cold end of the stack. */
ptr_t stack_ptr; /* Valid only when stopped. */
# ifdef IA64
ptr_t backing_store_end;
ptr_t backing_store_ptr;
# endif
int signal;
void * status; /* The value returned from the thread. */
/* Used only to avoid premature */
/* reclamation of any data it might */
/* reference. */
# ifdef THREAD_LOCAL_ALLOC
# if CPP_WORDSZ == 64 && defined(ALIGN_DOUBLE)
# define GRANULARITY 16
# define NFREELISTS 49
# else
# define GRANULARITY 8
# define NFREELISTS 65
# endif
/* The ith free list corresponds to size i*GRANULARITY */
# define INDEX_FROM_BYTES(n) ((ADD_SLOP(n) + GRANULARITY - 1)/GRANULARITY)
# define BYTES_FROM_INDEX(i) ((i) * GRANULARITY - EXTRA_BYTES)
# define SMALL_ENOUGH(bytes) (ADD_SLOP(bytes) <= \
(NFREELISTS-1)*GRANULARITY)
ptr_t ptrfree_freelists[NFREELISTS];
ptr_t normal_freelists[NFREELISTS];
# ifdef GC_GCJ_SUPPORT
ptr_t gcj_freelists[NFREELISTS];
# endif
/* Free lists contain either a pointer or a small count */
/* reflecting the number of granules allocated at that */
/* size. */
/* 0 ==> thread-local allocation in use, free list */
/* empty. */
/* > 0, <= DIRECT_GRANULES ==> Using global allocation, */
/* too few objects of this size have been */
/* allocated by this thread. */
/* >= HBLKSIZE => pointer to nonempty free list. */
/* > DIRECT_GRANULES, < HBLKSIZE ==> transition to */
/* local alloc, equivalent to 0. */
# define DIRECT_GRANULES (HBLKSIZE/GRANULARITY)
/* Don't use local free lists for up to this much */
/* allocation. */
# endif
} * GC_thread;
GC_thread GC_lookup_thread(pthread_t id);
static GC_bool parallel_initialized = FALSE;
# if defined(__GNUC__)
void GC_init_parallel() __attribute__ ((constructor));
# else
void GC_init_parallel();
# endif
# if defined(THREAD_LOCAL_ALLOC) && !defined(DBG_HDRS_ALL)
/* We don't really support thread-local allocation with DBG_HDRS_ALL */
#ifdef USE_HPUX_TLS
__thread
#endif
GC_key_t GC_thread_key;
static GC_bool keys_initialized;
/* Recover the contents of the freelist array fl into the global one gfl.*/
/* Note that the indexing scheme differs, in that gfl has finer size */
/* resolution, even if not all entries are used. */
/* We hold the allocator lock. */
static void return_freelists(ptr_t *fl, ptr_t *gfl)
{
int i;
ptr_t q, *qptr;
size_t nwords;
for (i = 1; i < NFREELISTS; ++i) {
nwords = i * (GRANULARITY/sizeof(word));
qptr = fl + i;
q = *qptr;
if ((word)q < HBLKSIZE) continue;
if (gfl[nwords] == 0) {
gfl[nwords] = q;
} else {
/* Concatenate: */
for (; (word)q >= HBLKSIZE; qptr = &(obj_link(q)), q = *qptr);
GC_ASSERT(0 == q);
*qptr = gfl[nwords];
gfl[nwords] = fl[i];
}
/* Clear fl[i], since the thread structure may hang around. */
/* Do it in a way that is likely to trap if we access it. */
fl[i] = (ptr_t)HBLKSIZE;
}
}
/* We statically allocate a single "size 0" object. It is linked to */
/* itself, and is thus repeatedly reused for all size 0 allocation */
/* requests. (Size 0 gcj allocation requests are incorrect, and */
/* we arrange for those to fault asap.) */
static ptr_t size_zero_object = (ptr_t)(&size_zero_object);
/* Each thread structure must be initialized. */
/* This call must be made from the new thread. */
/* Caller holds allocation lock. */
void GC_init_thread_local(GC_thread p)
{
int i;
if (!keys_initialized) {
if (0 != GC_key_create(&GC_thread_key, 0)) {
ABORT("Failed to create key for local allocator");
}
keys_initialized = TRUE;
}
if (0 != GC_setspecific(GC_thread_key, p)) {
ABORT("Failed to set thread specific allocation pointers");
}
for (i = 1; i < NFREELISTS; ++i) {
p -> ptrfree_freelists[i] = (ptr_t)1;
p -> normal_freelists[i] = (ptr_t)1;
# ifdef GC_GCJ_SUPPORT
p -> gcj_freelists[i] = (ptr_t)1;
# endif
}
/* Set up the size 0 free lists. */
p -> ptrfree_freelists[0] = (ptr_t)(&size_zero_object);
p -> normal_freelists[0] = (ptr_t)(&size_zero_object);
# ifdef GC_GCJ_SUPPORT
p -> gcj_freelists[0] = (ptr_t)(-1);
# endif
}
#ifdef GC_GCJ_SUPPORT
extern ptr_t * GC_gcjobjfreelist;
#endif
/* We hold the allocator lock. */
void GC_destroy_thread_local(GC_thread p)
{
/* We currently only do this from the thread itself. */
GC_ASSERT(GC_getspecific(GC_thread_key) == (void *)p);
return_freelists(p -> ptrfree_freelists, GC_aobjfreelist);
return_freelists(p -> normal_freelists, GC_objfreelist);
# ifdef GC_GCJ_SUPPORT
return_freelists(p -> gcj_freelists, GC_gcjobjfreelist);
# endif
}
extern GC_PTR GC_generic_malloc_many();
GC_PTR GC_local_malloc(size_t bytes)
{
if (EXPECT(!SMALL_ENOUGH(bytes),0)) {
return(GC_malloc(bytes));
} else {
int index = INDEX_FROM_BYTES(bytes);
ptr_t * my_fl;
ptr_t my_entry;
GC_key_t k = GC_thread_key;
void * tsd;
# if defined(REDIRECT_MALLOC) && !defined(USE_PTHREAD_SPECIFIC) \
|| !defined(__GNUC__)
if (EXPECT(0 == k, 0)) {
/* This can happen if we get called when the world is */
/* being initialized. Whether we can actually complete */
/* the initialization then is unclear. */
GC_init_parallel();
k = GC_thread_key;
}
# endif
tsd = GC_getspecific(GC_thread_key);
# ifdef GC_ASSERTIONS
LOCK();
GC_ASSERT(tsd == (void *)GC_lookup_thread(pthread_self()));
UNLOCK();
# endif
my_fl = ((GC_thread)tsd) -> normal_freelists + index;
my_entry = *my_fl;
if (EXPECT((word)my_entry >= HBLKSIZE, 1)) {
ptr_t next = obj_link(my_entry);
GC_PTR result = (GC_PTR)my_entry;
*my_fl = next;
obj_link(my_entry) = 0;
PREFETCH_FOR_WRITE(next);
return result;
} else if ((word)my_entry - 1 < DIRECT_GRANULES) {
*my_fl = my_entry + index + 1;
return GC_malloc(bytes);
} else {
GC_generic_malloc_many(BYTES_FROM_INDEX(index), NORMAL, my_fl);
if (*my_fl == 0) return GC_oom_fn(bytes);
return GC_local_malloc(bytes);
}
}
}
GC_PTR GC_local_malloc_atomic(size_t bytes)
{
if (EXPECT(!SMALL_ENOUGH(bytes), 0)) {
return(GC_malloc_atomic(bytes));
} else {
int index = INDEX_FROM_BYTES(bytes);
ptr_t * my_fl = ((GC_thread)GC_getspecific(GC_thread_key))
-> ptrfree_freelists + index;
ptr_t my_entry = *my_fl;
if (EXPECT((word)my_entry >= HBLKSIZE, 1)) {
GC_PTR result = (GC_PTR)my_entry;
*my_fl = obj_link(my_entry);
return result;
} else if ((word)my_entry - 1 < DIRECT_GRANULES) {
*my_fl = my_entry + index + 1;
return GC_malloc_atomic(bytes);
} else {
GC_generic_malloc_many(BYTES_FROM_INDEX(index), PTRFREE, my_fl);
/* *my_fl is updated while the collector is excluded; */
/* the free list is always visible to the collector as */
/* such. */
if (*my_fl == 0) return GC_oom_fn(bytes);
return GC_local_malloc_atomic(bytes);
}
}
}
#ifdef GC_GCJ_SUPPORT
#include "include/gc_gcj.h"
#ifdef GC_ASSERTIONS
extern GC_bool GC_gcj_malloc_initialized;
#endif
extern int GC_gcj_kind;
GC_PTR GC_local_gcj_malloc(size_t bytes,
void * ptr_to_struct_containing_descr)
{
GC_ASSERT(GC_gcj_malloc_initialized);
if (EXPECT(!SMALL_ENOUGH(bytes), 0)) {
return GC_gcj_malloc(bytes, ptr_to_struct_containing_descr);
} else {
int index = INDEX_FROM_BYTES(bytes);
ptr_t * my_fl = ((GC_thread)GC_getspecific(GC_thread_key))
-> gcj_freelists + index;
ptr_t my_entry = *my_fl;
if (EXPECT((word)my_entry >= HBLKSIZE, 1)) {
GC_PTR result = (GC_PTR)my_entry;
GC_ASSERT(!GC_incremental);
/* We assert that any concurrent marker will stop us. */
/* Thus it is impossible for a mark procedure to see the */
/* allocation of the next object, but to see this object */
/* still containing a free list pointer. Otherwise the */
/* marker might find a random "mark descriptor". */
*(volatile ptr_t *)my_fl = obj_link(my_entry);
/* We must update the freelist before we store the pointer. */
/* Otherwise a GC at this point would see a corrupted */
/* free list. */
/* A memory barrier is probably never needed, since the */
/* action of stopping this thread will cause prior writes */
/* to complete. */
*(void * volatile *)result = ptr_to_struct_containing_descr;
return result;
} else if ((word)my_entry - 1 < DIRECT_GRANULES) {
*my_fl = my_entry + index + 1;
return GC_gcj_malloc(bytes, ptr_to_struct_containing_descr);
} else {
GC_generic_malloc_many(BYTES_FROM_INDEX(index), GC_gcj_kind, my_fl);
if (*my_fl == 0) return GC_oom_fn(bytes);
return GC_local_gcj_malloc(bytes, ptr_to_struct_containing_descr);
}
}
}
#endif /* GC_GCJ_SUPPORT */
# else /* !THREAD_LOCAL_ALLOC && !DBG_HDRS_ALL */
# define GC_destroy_thread_local(t)
# endif /* !THREAD_LOCAL_ALLOC */
/*
* We use signals to stop threads during GC.
*
* Suspended threads wait in signal handler for SIG_THR_RESTART.
* That's more portable than semaphores or condition variables.
* (We do use sem_post from a signal handler, but that should be portable.)
*
* The thread suspension signal SIG_SUSPEND is now defined in gc_priv.h.
* Note that we can't just stop a thread; we need it to save its stack
* pointer(s) and acknowledge.
*/
#ifndef SIG_THR_RESTART
# if defined(HPUX_THREADS) || defined(GC_OSF1_THREADS)
# define SIG_THR_RESTART _SIGRTMIN + 5
# else
# define SIG_THR_RESTART SIGXCPU
# endif
#endif
sem_t GC_suspend_ack_sem;
#if !defined(HPUX_THREADS) && !defined(GC_OSF1_THREADS)
/*
To make sure that we're using LinuxThreads and not some other thread
package, we generate a dummy reference to `pthread_kill_other_threads_np'
(was `__pthread_initial_thread_bos' but that disappeared),
which is a symbol defined in LinuxThreads, but (hopefully) not in other
thread packages.
*/
void (*dummy_var_to_force_linux_threads)() = pthread_kill_other_threads_np;
#endif /* !HPUX_THREADS */
#if defined(SPARC) || defined(IA64)
extern word GC_save_regs_in_stack();
#endif
long GC_nprocs = 1; /* Number of processors. We may not have */
/* access to all of them, but this is as good */
/* a guess as any ... */
#ifdef PARALLEL_MARK
# ifndef MAX_MARKERS
# define MAX_MARKERS 16
# endif
static ptr_t marker_sp[MAX_MARKERS] = {0};
void * GC_mark_thread(void * id)
{
word my_mark_no = 0;
marker_sp[(word)id] = GC_approx_sp();
for (;; ++my_mark_no) {
/* GC_mark_no is passed only to allow GC_help_marker to terminate */
/* promptly. This is important if it were called from the signal */
/* handler or from the GC lock acquisition code. Under Linux, it's */
/* not safe to call it from a signal handler, since it uses mutexes */
/* and condition variables. Since it is called only here, the */
/* argument is unnecessary. */
if (my_mark_no < GC_mark_no || my_mark_no > GC_mark_no + 2) {
/* resynchronize if we get far off, e.g. because GC_mark_no */
/* wrapped. */
my_mark_no = GC_mark_no;
}
# ifdef DEBUG_THREADS
GC_printf1("Starting mark helper for mark number %ld\n", my_mark_no);
# endif
GC_help_marker(my_mark_no);
}
}
extern long GC_markers; /* Number of mark threads we would */
/* like to have. Includes the */
/* initiating thread. */
pthread_t GC_mark_threads[MAX_MARKERS];
#define PTHREAD_CREATE REAL_FUNC(pthread_create)
static void start_mark_threads()
{
unsigned i;
pthread_attr_t attr;
if (GC_markers > MAX_MARKERS) {
WARN("Limiting number of mark threads\n", 0);
GC_markers = MAX_MARKERS;
}
if (0 != pthread_attr_init(&attr)) ABORT("pthread_attr_init failed");
if (0 != pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED))
ABORT("pthread_attr_setdetachstate failed");
# ifdef CONDPRINT
if (GC_print_stats) {
GC_printf1("Starting %ld marker threads\n", GC_markers - 1);
}
# endif
for (i = 0; i < GC_markers - 1; ++i) {
if (0 != PTHREAD_CREATE(GC_mark_threads + i, &attr,
GC_mark_thread, (void *)(word)i)) {
WARN("Marker thread creation failed, errno = %ld.\n", errno);
}
}
}
#else /* !PARALLEL_MARK */
static __inline__ void start_mark_threads()
{
}
#endif /* !PARALLEL_MARK */
void GC_suspend_handler(int sig)
{
int dummy;
pthread_t my_thread = pthread_self();
GC_thread me;
sigset_t all_sigs;
sigset_t old_sigs;
int i;
sigset_t mask;
# ifdef PARALLEL_MARK
word my_mark_no = GC_mark_no;
/* Marker can't proceed until we acknowledge. Thus this is */
/* guaranteed to be the mark_no correspending to our */
/* suspension, i.e. the marker can't have incremented it yet. */
# endif
if (sig != SIG_SUSPEND) ABORT("Bad signal in suspend_handler");
#if DEBUG_THREADS
GC_printf1("Suspending 0x%x\n", my_thread);
#endif
me = GC_lookup_thread(my_thread);
/* The lookup here is safe, since I'm doing this on behalf */
/* of a thread which holds the allocation lock in order */
/* to stop the world. Thus concurrent modification of the */
/* data structure is impossible. */
# ifdef SPARC
me -> stack_ptr = (ptr_t)GC_save_regs_in_stack();
# else
me -> stack_ptr = (ptr_t)(&dummy);
# endif
# ifdef IA64
me -> backing_store_ptr = (ptr_t)GC_save_regs_in_stack();
# endif
/* Tell the thread that wants to stop the world that this */
/* thread has been stopped. Note that sem_post() is */
/* the only async-signal-safe primitive in LinuxThreads. */
sem_post(&GC_suspend_ack_sem);
/* Wait until that thread tells us to restart by sending */
/* this thread a SIG_THR_RESTART signal. */
/* SIG_THR_RESTART should be masked at this point. Thus there */
/* is no race. */
if (sigfillset(&mask) != 0) ABORT("sigfillset() failed");
if (sigdelset(&mask, SIG_THR_RESTART) != 0) ABORT("sigdelset() failed");
# ifdef NO_SIGNALS
if (sigdelset(&mask, SIGINT) != 0) ABORT("sigdelset() failed");
if (sigdelset(&mask, SIGQUIT) != 0) ABORT("sigdelset() failed");
if (sigdelset(&mask, SIGTERM) != 0) ABORT("sigdelset() failed");
if (sigdelset(&mask, SIGABRT) != 0) ABORT("sigdelset() failed");
# endif
do {
me->signal = 0;
sigsuspend(&mask); /* Wait for signal */
} while (me->signal != SIG_THR_RESTART);
#if DEBUG_THREADS
GC_printf1("Continuing 0x%x\n", my_thread);
#endif
}
void GC_restart_handler(int sig)
{
GC_thread me;
if (sig != SIG_THR_RESTART) ABORT("Bad signal in suspend_handler");
/* Let the GC_suspend_handler() know that we got a SIG_THR_RESTART. */
/* The lookup here is safe, since I'm doing this on behalf */
/* of a thread which holds the allocation lock in order */
/* to stop the world. Thus concurrent modification of the */
/* data structure is impossible. */
me = GC_lookup_thread(pthread_self());
me->signal = SIG_THR_RESTART;
/*
** Note: even if we didn't do anything useful here,
** it would still be necessary to have a signal handler,
** rather than ignoring the signals, otherwise
** the signals will not be delivered at all, and
** will thus not interrupt the sigsuspend() above.
*/
#if DEBUG_THREADS
GC_printf1("In GC_restart_handler for 0x%x\n", pthread_self());
#endif
}
/* Defining INSTALL_LOOPING_SEGV_HANDLER causes SIGSEGV and SIGBUS to */
/* result in an infinite loop in a signal handler. This can be very */
/* useful for debugging, since (as of RH7) gdb still seems to have */
/* serious problems with threads. */
#ifdef INSTALL_LOOPING_SEGV_HANDLER
void GC_looping_handler(int sig)
{
GC_printf3("Signal %ld in thread %lx, pid %ld\n",
sig, pthread_self(), getpid());
for (;;);
}
#endif
GC_bool GC_thr_initialized = FALSE;
# define THREAD_TABLE_SZ 128 /* Must be power of 2 */
volatile GC_thread GC_threads[THREAD_TABLE_SZ];
void GC_push_thread_structures GC_PROTO((void))
{
GC_push_all((ptr_t)(GC_threads), (ptr_t)(GC_threads)+sizeof(GC_threads));
}
#ifdef THREAD_LOCAL_ALLOC
/* We must explicitly mark ptrfree and gcj free lists, since the free */
/* list links wouldn't otherwise be found. We also set them in the */
/* normal free lists, since that involves touching less memory than if */
/* we scanned them normally. */
void GC_mark_thread_local_free_lists(void)
{
int i, j;
GC_thread p;
ptr_t q;
for (i = 0; i < THREAD_TABLE_SZ; ++i) {
for (p = GC_threads[i]; 0 != p; p = p -> next) {
for (j = 1; j < NFREELISTS; ++j) {
q = p -> ptrfree_freelists[j];
if ((word)q > HBLKSIZE) GC_set_fl_marks(q);
q = p -> normal_freelists[j];
if ((word)q > HBLKSIZE) GC_set_fl_marks(q);
# ifdef GC_GCJ_SUPPORT
q = p -> gcj_freelists[j];
if ((word)q > HBLKSIZE) GC_set_fl_marks(q);
# endif /* GC_GCJ_SUPPORT */
}
}
}
}
#endif /* THREAD_LOCAL_ALLOC */
/* Add a thread to GC_threads. We assume it wasn't already there. */
/* Caller holds allocation lock. */
GC_thread GC_new_thread(pthread_t id)
{
int hv = ((word)id) % THREAD_TABLE_SZ;
GC_thread result;
static struct GC_Thread_Rep first_thread;
static GC_bool first_thread_used = FALSE;
if (!first_thread_used) {
result = &first_thread;
first_thread_used = TRUE;
} else {
result = (struct GC_Thread_Rep *)
GC_INTERNAL_MALLOC(sizeof(struct GC_Thread_Rep), NORMAL);
}
if (result == 0) return(0);
result -> id = id;
result -> next = GC_threads[hv];
GC_threads[hv] = result;
GC_ASSERT(result -> flags == 0 && result -> thread_blocked == 0);
return(result);
}
/* Delete a thread from GC_threads. We assume it is there. */
/* (The code intentionally traps if it wasn't.) */
/* Caller holds allocation lock. */
void GC_delete_thread(pthread_t id)
{
int hv = ((word)id) % THREAD_TABLE_SZ;
register GC_thread p = GC_threads[hv];
register GC_thread prev = 0;
while (!pthread_equal(p -> id, id)) {
prev = p;
p = p -> next;
}
if (prev == 0) {
GC_threads[hv] = p -> next;
} else {
prev -> next = p -> next;
}
GC_INTERNAL_FREE(p);
}
/* If a thread has been joined, but we have not yet */
/* been notified, then there may be more than one thread */
/* in the table with the same pthread id. */
/* This is OK, but we need a way to delete a specific one. */
void GC_delete_gc_thread(pthread_t id, GC_thread gc_id)
{
int hv = ((word)id) % THREAD_TABLE_SZ;
register GC_thread p = GC_threads[hv];
register GC_thread prev = 0;
while (p != gc_id) {
prev = p;
p = p -> next;
}
if (prev == 0) {
GC_threads[hv] = p -> next;
} else {
prev -> next = p -> next;
}
GC_INTERNAL_FREE(p);
}
/* Return a GC_thread corresponding to a given thread_t. */
/* Returns 0 if it's not there. */
/* Caller holds allocation lock or otherwise inhibits */
/* updates. */
/* If there is more than one thread with the given id we */
/* return the most recent one. */
GC_thread GC_lookup_thread(pthread_t id)
{
int hv = ((word)id) % THREAD_TABLE_SZ;
register GC_thread p = GC_threads[hv];
while (p != 0 && !pthread_equal(p -> id, id)) p = p -> next;
return(p);
}
/* There seems to be a very rare thread stopping problem. To help us */
/* debug that, we save the ids of the stopping thread. */
pthread_t GC_stopping_thread;
int GC_stopping_pid;
/* Caller holds allocation lock. */
void GC_stop_world()
{
pthread_t my_thread = pthread_self();
register int i;
register GC_thread p;
register int n_live_threads = 0;
register int result;
GC_stopping_thread = my_thread; /* debugging only. */
GC_stopping_pid = getpid(); /* debugging only. */
/* Make sure all free list construction has stopped before we start. */
/* No new construction can start, since free list construction is */
/* required to acquire and release the GC lock before it starts, */
/* and we have the lock. */
# ifdef PARALLEL_MARK
GC_acquire_mark_lock();
GC_ASSERT(GC_fl_builder_count == 0);
/* We should have previously waited for it to become zero. */
# endif /* PARALLEL_MARK */
for (i = 0; i < THREAD_TABLE_SZ; i++) {
for (p = GC_threads[i]; p != 0; p = p -> next) {
if (p -> id != my_thread) {
if (p -> flags & FINISHED) continue;
if (p -> thread_blocked) /* Will wait */ continue;
n_live_threads++;
#if DEBUG_THREADS
GC_printf1("Sending suspend signal to 0x%x\n", p -> id);
#endif
result = pthread_kill(p -> id, SIG_SUSPEND);
switch(result) {
case ESRCH:
/* Not really there anymore. Possible? */
n_live_threads--;
break;
case 0:
break;
default:
ABORT("pthread_kill failed");
}
}
}
}
for (i = 0; i < n_live_threads; i++) {
if (0 != sem_wait(&GC_suspend_ack_sem))
ABORT("sem_wait in handler failed");
}
# ifdef PARALLEL_MARK
GC_release_mark_lock();
# endif
#if DEBUG_THREADS
GC_printf1("World stopped 0x%x\n", pthread_self());
#endif
GC_stopping_thread = 0; /* debugging only */
}
/* Caller holds allocation lock, and has held it continuously since */
/* the world stopped. */
void GC_start_world()
{
pthread_t my_thread = pthread_self();
register int i;
register GC_thread p;
register int n_live_threads = 0;
register int result;
# if DEBUG_THREADS
GC_printf0("World starting\n");
# endif
for (i = 0; i < THREAD_TABLE_SZ; i++) {
for (p = GC_threads[i]; p != 0; p = p -> next) {
if (p -> id != my_thread) {
if (p -> flags & FINISHED) continue;
if (p -> thread_blocked) continue;
n_live_threads++;
#if DEBUG_THREADS
GC_printf1("Sending restart signal to 0x%x\n", p -> id);
#endif
result = pthread_kill(p -> id, SIG_THR_RESTART);
switch(result) {
case ESRCH:
/* Not really there anymore. Possible? */
n_live_threads--;
break;
case 0:
break;
default:
ABORT("pthread_kill failed");
}
}
}
}
#if DEBUG_THREADS
GC_printf0("World started\n");
#endif
GC_stopping_thread = 0; /* debugging only */
}
# ifdef IA64
# define IF_IA64(x) x
# else
# define IF_IA64(x)
# endif
/* We hold allocation lock. Should do exactly the right thing if the */
/* world is stopped. Should not fail if it isn't. */
void GC_push_all_stacks()
{
int i;
GC_thread p;
ptr_t sp = GC_approx_sp();
ptr_t lo, hi;
/* On IA64, we also need to scan the register backing store. */
IF_IA64(ptr_t bs_lo; ptr_t bs_hi;)
pthread_t me = pthread_self();
if (!GC_thr_initialized) GC_thr_init();
#if DEBUG_THREADS
GC_printf1("Pushing stacks from thread 0x%lx\n", (unsigned long) me);
#endif
for (i = 0; i < THREAD_TABLE_SZ; i++) {
for (p = GC_threads[i]; p != 0; p = p -> next) {
if (p -> flags & FINISHED) continue;
if (pthread_equal(p -> id, me)) {
# ifdef SPARC
lo = (ptr_t)GC_save_regs_in_stack();
# else
lo = GC_approx_sp();
# endif
IF_IA64(bs_hi = (ptr_t)GC_save_regs_in_stack();)
} else {
lo = p -> stack_ptr;
IF_IA64(bs_hi = p -> backing_store_ptr;)
}
if ((p -> flags & MAIN_THREAD) == 0) {
hi = p -> stack_end;
IF_IA64(bs_lo = p -> backing_store_end);
} else {
/* The original stack. */
hi = GC_stackbottom;
IF_IA64(bs_lo = BACKING_STORE_BASE;)
}
#if DEBUG_THREADS
GC_printf3("Stack for thread 0x%lx = [%lx,%lx)\n",
(unsigned long) p -> id,
(unsigned long) lo, (unsigned long) hi);
#endif
if (0 == lo) ABORT("GC_push_all_stacks: sp not set!\n");
# ifdef STACK_GROWS_UP
/* We got them backwards! */
GC_push_all_stack(hi, lo);
# else
GC_push_all_stack(lo, hi);
# endif
# ifdef IA64
if (pthread_equal(p -> id, me)) {
GC_push_all_eager(bs_lo, bs_hi);
} else {
GC_push_all_stack(bs_lo, bs_hi);
}
# endif
}
}
}
#ifdef USE_PROC_FOR_LIBRARIES
int GC_segment_is_thread_stack(ptr_t lo, ptr_t hi)
{
int i;
GC_thread p;
# ifdef PARALLEL_MARK
for (i = 0; i < GC_markers; ++i) {
if (marker_sp[i] > lo & marker_sp[i] < hi) return 1;
}
# endif
for (i = 0; i < THREAD_TABLE_SZ; i++) {
for (p = GC_threads[i]; p != 0; p = p -> next) {
if (0 != p -> stack_end) {
# ifdef STACK_GROWS_UP
if (p -> stack_end >= lo && p -> stack_end < hi) return 1;
# else /* STACK_GROWS_DOWN */
if (p -> stack_end > lo && p -> stack_end <= hi) return 1;
# endif
}
}
}
return 0;
}
#endif /* USE_PROC_FOR_LIBRARIES */
#ifdef LINUX_THREADS
/* Return the number of processors, or i<= 0 if it can't be determined. */
int GC_get_nprocs()
{
/* Should be "return sysconf(_SC_NPROCESSORS_ONLN);" but that */
/* appears to be buggy in many cases. */
/* We look for lines "cpu<n>" in /proc/stat. */
# define STAT_BUF_SIZE 4096
# if defined(GC_USE_LD_WRAP)
# define STAT_READ __real_read
# else
# define STAT_READ read
# endif
char stat_buf[STAT_BUF_SIZE];
int f;
char c;
word result = 1;
/* Some old kernels only have a single "cpu nnnn ..." */
/* entry in /proc/stat. We identify those as */
/* uniprocessors. */
size_t i, len = 0;
f = open("/proc/stat", O_RDONLY);
if (f < 0 || (len = STAT_READ(f, stat_buf, STAT_BUF_SIZE)) < 100) {
WARN("Couldn't read /proc/stat\n", 0);
return -1;
}
for (i = 0; i < len - 100; ++i) {
if (stat_buf[i] == '\n' && stat_buf[i+1] == 'c'
&& stat_buf[i+2] == 'p' && stat_buf[i+3] == 'u') {
int cpu_no = atoi(stat_buf + i + 4);
if (cpu_no >= result) result = cpu_no + 1;
}
}
return result;
}
#endif /* LINUX_THREADS */
/* We hold the allocation lock. */
void GC_thr_init()
{
int dummy;
GC_thread t;
struct sigaction act;
if (GC_thr_initialized) return;
GC_thr_initialized = TRUE;
if (sem_init(&GC_suspend_ack_sem, 0, 0) != 0)
ABORT("sem_init failed");
act.sa_flags = SA_RESTART;
if (sigfillset(&act.sa_mask) != 0) {
ABORT("sigfillset() failed");
}
# ifdef NO_SIGNALS
if (sigdelset(&act.sa_mask, SIGINT) != 0
|| sigdelset(&act.sa_mask, SIGQUIT != 0)
|| sigdelset(&act.sa_mask, SIGABRT != 0)
|| sigdelset(&act.sa_mask, SIGTERM != 0)) {
ABORT("sigdelset() failed");
}
# endif
/* SIG_THR_RESTART is unmasked by the handler when necessary. */
act.sa_handler = GC_suspend_handler;
if (sigaction(SIG_SUSPEND, &act, NULL) != 0) {
ABORT("Cannot set SIG_SUSPEND handler");
}
act.sa_handler = GC_restart_handler;
if (sigaction(SIG_THR_RESTART, &act, NULL) != 0) {
ABORT("Cannot set SIG_THR_RESTART handler");
}
# ifdef INSTALL_LOOPING_SEGV_HANDLER
act.sa_handler = GC_looping_handler;
if (sigaction(SIGSEGV, &act, NULL) != 0
|| sigaction(SIGBUS, &act, NULL) != 0) {
ABORT("Cannot set SIGSEGV or SIGBUS looping handler");
}
# endif /* INSTALL_LOOPING_SEGV_HANDLER */
/* Add the initial thread, so we can stop it. */
t = GC_new_thread(pthread_self());
t -> stack_ptr = (ptr_t)(&dummy);
t -> flags = DETACHED | MAIN_THREAD;
/* Set GC_nprocs. */
{
char * nprocs_string = GETENV("GC_NPROCS");
GC_nprocs = -1;
if (nprocs_string != NULL) GC_nprocs = atoi(nprocs_string);
}
if (GC_nprocs <= 0) {
# if defined(HPUX_THREADS)
GC_nprocs = pthread_num_processors_np();
# endif
# if defined(OSF1_THREADS)
GC_nprocs = 1;
# endif
# ifdef LINUX_THREADS
GC_nprocs = GC_get_nprocs();
# endif
}
if (GC_nprocs <= 0) {
WARN("GC_get_nprocs() returned %ld\n", GC_nprocs);
GC_nprocs = 2;
# ifdef PARALLEL_MARK
GC_markers = 1;
# endif
} else {
# ifdef PARALLEL_MARK
GC_markers = GC_nprocs;
# endif
}
# ifdef PARALLEL_MARK
# ifdef CONDPRINT
if (GC_print_stats) {
GC_printf2("Number of processors = %ld, "
"number of marker threads = %ld\n", GC_nprocs, GC_markers);
}
# endif
if (GC_markers == 1) {
GC_parallel = FALSE;
# ifdef CONDPRINT
if (GC_print_stats) {
GC_printf0("Single marker thread, turning off parallel marking\n");
}
# endif
} else {
GC_parallel = TRUE;
}
# endif
}
/* Perform all initializations, including those that */
/* may require allocation. */
/* Called as constructor without allocation lock. */
/* Must be called before a second thread is created. */
/* Called without allocation lock. */
void GC_init_parallel()
{
if (parallel_initialized) return;
parallel_initialized = TRUE;
/* GC_init() calls us back, so set flag first. */
if (!GC_is_initialized) GC_init();
/* If we are using a parallel marker, start the helper threads. */
# ifdef PARALLEL_MARK
if (GC_parallel) start_mark_threads();
# endif
/* Initialize thread local free lists if used. */
# if defined(THREAD_LOCAL_ALLOC) && !defined(DBG_HDRS_ALL)
LOCK();
GC_init_thread_local(GC_lookup_thread(pthread_self()));
UNLOCK();
# endif
}
int WRAP_FUNC(pthread_sigmask)(int how, const sigset_t *set, sigset_t *oset)
{
sigset_t fudged_set;
if (set != NULL && (how == SIG_BLOCK || how == SIG_SETMASK)) {
fudged_set = *set;
sigdelset(&fudged_set, SIG_SUSPEND);
set = &fudged_set;
}
return(REAL_FUNC(pthread_sigmask)(how, set, oset));
}
/* Wrappers for functions that are likely to block for an appreciable */
/* length of time. Must be called in pairs, if at all. */
/* Nothing much beyond the system call itself should be executed */
/* between these. */
void GC_start_blocking(void) {
# define SP_SLOP 128
GC_thread me;
LOCK();
me = GC_lookup_thread(pthread_self());
GC_ASSERT(!(me -> thread_blocked));
# ifdef SPARC
me -> stack_ptr = (ptr_t)GC_save_regs_in_stack();
# else
me -> stack_ptr = (ptr_t)GC_approx_sp();
# endif
# ifdef IA64
me -> backing_store_ptr = (ptr_t)GC_save_regs_in_stack() + SP_SLOP;
# endif
/* Add some slop to the stack pointer, since the wrapped call may */
/* end up pushing more callee-save registers. */
# ifdef STACK_GROWS_UP
me -> stack_ptr += SP_SLOP;
# else
me -> stack_ptr -= SP_SLOP;
# endif
me -> thread_blocked = TRUE;
UNLOCK();
}
GC_end_blocking(void) {
GC_thread me;
LOCK(); /* This will block if the world is stopped. */
me = GC_lookup_thread(pthread_self());
GC_ASSERT(me -> thread_blocked);
me -> thread_blocked = FALSE;
UNLOCK();
}
/* A wrapper for the standard C sleep function */
int WRAP_FUNC(sleep) (unsigned int seconds)
{
int result;
GC_start_blocking();
result = REAL_FUNC(sleep)(seconds);
GC_end_blocking();
return result;
}
struct start_info {
void *(*start_routine)(void *);
void *arg;
word flags;
sem_t registered; /* 1 ==> in our thread table, but */
/* parent hasn't yet noticed. */
};
/* Called at thread exit. */
/* Never called for main thread. That's OK, since it */
/* results in at most a tiny one-time leak. And */
/* linuxthreads doesn't reclaim the main threads */
/* resources or id anyway. */
void GC_thread_exit_proc(void *arg)
{
GC_thread me;
LOCK();
me = GC_lookup_thread(pthread_self());
GC_destroy_thread_local(me);
if (me -> flags & DETACHED) {
GC_delete_thread(pthread_self());
} else {
me -> flags |= FINISHED;
}
# if defined(THREAD_LOCAL_ALLOC) && !defined(USE_PTHREAD_SPECIFIC) \
&& !defined(USE_HPUX_TLS) && !defined(DBG_HDRS_ALL)
GC_remove_specific(GC_thread_key);
# endif
if (GC_incremental && GC_collection_in_progress()) {
int old_gc_no = GC_gc_no;
/* Make sure that no part of our stack is still on the mark stack, */
/* since it's about to be unmapped. */
while (GC_incremental && GC_collection_in_progress()
&& old_gc_no == GC_gc_no) {
ENTER_GC();
GC_collect_a_little_inner(1);
EXIT_GC();
UNLOCK();
sched_yield();
LOCK();
}
}
UNLOCK();
}
int WRAP_FUNC(pthread_join)(pthread_t thread, void **retval)
{
int result;
GC_thread thread_gc_id;
LOCK();
thread_gc_id = GC_lookup_thread(thread);
/* This is guaranteed to be the intended one, since the thread id */
/* cant have been recycled by pthreads. */
UNLOCK();
result = REAL_FUNC(pthread_join)(thread, retval);
if (result == 0) {
LOCK();
/* Here the pthread thread id may have been recycled. */
GC_delete_gc_thread(thread, thread_gc_id);
UNLOCK();
}
return result;
}
int
WRAP_FUNC(pthread_detach)(pthread_t thread)
{
int result;
GC_thread thread_gc_id;
LOCK();
thread_gc_id = GC_lookup_thread(thread);
UNLOCK();
result = REAL_FUNC(pthread_detach)(thread);
if (result == 0) {
LOCK();
thread_gc_id -> flags |= DETACHED;
/* Here the pthread thread id may have been recycled. */
if (thread_gc_id -> flags & FINISHED) {
GC_delete_gc_thread(thread, thread_gc_id);
}
UNLOCK();
}
return result;
}
void * GC_start_routine(void * arg)
{
int dummy;
struct start_info * si = arg;
void * result;
GC_thread me;
pthread_t my_pthread;
void *(*start)(void *);
void *start_arg;
my_pthread = pthread_self();
# ifdef DEBUG_THREADS
GC_printf1("Starting thread 0x%lx\n", my_pthread);
GC_printf1("pid = %ld\n", (long) getpid());
GC_printf1("sp = 0x%lx\n", (long) &arg);
# endif
LOCK();
me = GC_new_thread(my_pthread);
me -> flags = si -> flags;
me -> stack_ptr = 0;
/* me -> stack_end = GC_linux_stack_base(); -- currently (11/99) */
/* doesn't work because the stack base in /proc/self/stat is the */
/* one for the main thread. There is a strong argument that that's */
/* a kernel bug, but a pervasive one. */
# ifdef STACK_GROWS_DOWN
me -> stack_end = (ptr_t)(((word)(&dummy) + (GC_page_size - 1))
& ~(GC_page_size - 1));
me -> stack_ptr = me -> stack_end - 0x10;
/* Needs to be plausible, since an asynchronous stack mark */
/* should not crash. */
# else
me -> stack_end = (ptr_t)((word)(&dummy) & ~(GC_page_size - 1));
me -> stack_ptr = me -> stack_end + 0x10;
# endif
/* This is dubious, since we may be more than a page into the stack, */
/* and hence skip some of it, though it's not clear that matters. */
# ifdef IA64
me -> backing_store_end = (ptr_t)
(GC_save_regs_in_stack() & ~(GC_page_size - 1));
/* This is also < 100% convincing. We should also read this */
/* from /proc, but the hook to do so isn't there yet. */
# endif /* IA64 */
UNLOCK();
start = si -> start_routine;
# ifdef DEBUG_THREADS
GC_printf1("start_routine = 0x%lx\n", start);
# endif
start_arg = si -> arg;
sem_post(&(si -> registered)); /* Last action on si. */
/* OK to deallocate. */
pthread_cleanup_push(GC_thread_exit_proc, 0);
# if defined(THREAD_LOCAL_ALLOC) && !defined(DBG_HDRS_ALL)
LOCK();
GC_init_thread_local(me);
UNLOCK();
# endif
result = (*start)(start_arg);
#if DEBUG_THREADS
GC_printf1("Finishing thread 0x%x\n", pthread_self());
#endif
me -> status = result;
me -> flags |= FINISHED;
pthread_cleanup_pop(1);
/* Cleanup acquires lock, ensuring that we can't exit */
/* while a collection that thinks we're alive is trying to stop */
/* us. */
return(result);
}
int
WRAP_FUNC(pthread_create)(pthread_t *new_thread,
const pthread_attr_t *attr,
void *(*start_routine)(void *), void *arg)
{
int result;
GC_thread t;
pthread_t my_new_thread;
int detachstate;
word my_flags = 0;
struct start_info * si;
/* This is otherwise saved only in an area mmapped by the thread */
/* library, which isn't visible to the collector. */
LOCK();
si = (struct start_info *)GC_INTERNAL_MALLOC(sizeof(struct start_info), NORMAL);
UNLOCK();
if (!parallel_initialized) GC_init_parallel();
if (0 == si) return(ENOMEM);
sem_init(&(si -> registered), 0, 0);
si -> start_routine = start_routine;
si -> arg = arg;
LOCK();
if (!GC_thr_initialized) GC_thr_init();
if (NULL == attr) {
detachstate = PTHREAD_CREATE_JOINABLE;
} else {
pthread_attr_getdetachstate(attr, &detachstate);
}
if (PTHREAD_CREATE_DETACHED == detachstate) my_flags |= DETACHED;
si -> flags = my_flags;
UNLOCK();
# ifdef DEBUG_THREADS
GC_printf1("About to start new thread from thread 0x%X\n",
pthread_self());
# endif
result = REAL_FUNC(pthread_create)(new_thread, attr, GC_start_routine, si);
# ifdef DEBUG_THREADS
GC_printf1("Started thread 0x%X\n", *new_thread);
# endif
/* Wait until child has been added to the thread table. */
/* This also ensures that we hold onto si until the child is done */
/* with it. Thus it doesn't matter whether it is otherwise */
/* visible to the collector. */
while (0 != sem_wait(&(si -> registered))) {
if (EINTR != errno) ABORT("sem_wait failed");
}
sem_destroy(&(si -> registered));
LOCK();
GC_INTERNAL_FREE(si);
UNLOCK();
return(result);
}
#ifdef GENERIC_COMPARE_AND_SWAP
pthread_mutex_t GC_compare_and_swap_lock = PTHREAD_MUTEX_INITIALIZER;
GC_bool GC_compare_and_exchange(volatile GC_word *addr,
GC_word old, GC_word new_val)
{
GC_bool result;
pthread_mutex_lock(&GC_compare_and_swap_lock);
if (*addr == old) {
*addr = new_val;
result = TRUE;
} else {
result = FALSE;
}
pthread_mutex_unlock(&GC_compare_and_swap_lock);
return result;
}
GC_word GC_atomic_add(volatile GC_word *addr, GC_word how_much)
{
GC_word old;
pthread_mutex_lock(&GC_compare_and_swap_lock);
old = *addr;
*addr = old + how_much;
pthread_mutex_unlock(&GC_compare_and_swap_lock);
return old;
}
#endif /* GENERIC_COMPARE_AND_SWAP */
/* Spend a few cycles in a way that can't introduce contention with */
/* othre threads. */
void GC_pause()
{
int i;
volatile word dummy = 0;
for (i = 0; i < 10; ++i) {
# ifdef __GNUC__
__asm__ __volatile__ (" " : : : "memory");
# else
/* Something that's unlikely to be optimized away. */
GC_noop(++dummy);
# endif
}
}
#define SPIN_MAX 1024 /* Maximum number of calls to GC_pause before */
/* give up. */
VOLATILE GC_bool GC_collecting = 0;
/* A hint that we're in the collector and */
/* holding the allocation lock for an */
/* extended period. */
#if !defined(USE_SPIN_LOCK) || defined(PARALLEL_MARK)
/* If we don't want to use the below spinlock implementation, either */
/* because we don't have a GC_test_and_set implementation, or because */
/* we don't want to risk sleeping, we can still try spinning on */
/* pthread_mutex_trylock for a while. This appears to be very */
/* beneficial in many cases. */
/* I suspect that under high contention this is nearly always better */
/* than the spin lock. But it's a bit slower on a uniprocessor. */
/* Hence we still default to the spin lock. */
/* This is also used to acquire the mark lock for the parallel */
/* marker. */
/* Here we use a strict exponential backoff scheme. I don't know */
/* whether that's better or worse than the above. We eventually */
/* yield by calling pthread_mutex_lock(); it never makes sense to */
/* explicitly sleep. */
void GC_generic_lock(pthread_mutex_t * lock)
{
unsigned pause_length = 1;
unsigned i;
if (0 == pthread_mutex_trylock(lock)) return;
for (; pause_length <= SPIN_MAX; pause_length <<= 1) {
for (i = 0; i < pause_length; ++i) {
GC_pause();
}
switch(pthread_mutex_trylock(lock)) {
case 0:
return;
case EBUSY:
break;
default:
ABORT("Unexpected error from pthread_mutex_trylock");
}
}
pthread_mutex_lock(lock);
}
#endif /* !USE_SPIN_LOCK || PARALLEL_MARK */
#if defined(USE_SPIN_LOCK)
/* Reasonably fast spin locks. Basically the same implementation */
/* as STL alloc.h. This isn't really the right way to do this. */
/* but until the POSIX scheduling mess gets straightened out ... */
volatile unsigned int GC_allocate_lock = 0;
void GC_lock()
{
# define low_spin_max 30 /* spin cycles if we suspect uniprocessor */
# define high_spin_max SPIN_MAX /* spin cycles for multiprocessor */
static unsigned spin_max = low_spin_max;
unsigned my_spin_max;
static unsigned last_spins = 0;
unsigned my_last_spins;
int i;
if (!GC_test_and_set(&GC_allocate_lock)) {
return;
}
my_spin_max = spin_max;
my_last_spins = last_spins;
for (i = 0; i < my_spin_max; i++) {
if (GC_collecting || GC_nprocs == 1) goto yield;
if (i < my_last_spins/2 || GC_allocate_lock) {
GC_pause();
continue;
}
if (!GC_test_and_set(&GC_allocate_lock)) {
/*
* got it!
* Spinning worked. Thus we're probably not being scheduled
* against the other process with which we were contending.
* Thus it makes sense to spin longer the next time.
*/
last_spins = i;
spin_max = high_spin_max;
return;
}
}
/* We are probably being scheduled against the other process. Sleep. */
spin_max = low_spin_max;
yield:
for (i = 0;; ++i) {
if (!GC_test_and_set(&GC_allocate_lock)) {
return;
}
# define SLEEP_THRESHOLD 12
/* nanosleep(<= 2ms) just spins under Linux. We */
/* want to be careful to avoid that behavior. */
if (i < SLEEP_THRESHOLD) {
sched_yield();
} else {
struct timespec ts;
if (i > 24) i = 24;
/* Don't wait for more than about 15msecs, even */
/* under extreme contention. */
ts.tv_sec = 0;
ts.tv_nsec = 1 << i;
nanosleep(&ts, 0);
}
}
}
#else /* !USE_SPINLOCK */
void GC_lock()
{
if (1 == GC_nprocs || GC_collecting) {
pthread_mutex_lock(&GC_allocate_ml);
} else {
GC_generic_lock(&GC_allocate_ml);
}
}
#endif /* !USE_SPINLOCK */
#if defined(PARALLEL_MARK) || defined(THREAD_LOCAL_ALLOC)
#ifdef GC_ASSERTIONS
pthread_t GC_mark_lock_holder = NO_THREAD;
#endif
#ifdef IA64
/* Ugly workaround for a linux threads bug in the final versions */
/* of glibc2.1. Pthread_mutex_trylock sets the mutex owner */
/* field even when it fails to acquire the mutex. This causes */
/* pthread_cond_wait to die. Remove for glibc2.2. */
/* According to the man page, we should use */
/* PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP, but that isn't actually */
/* defined. */
static pthread_mutex_t mark_mutex =
{0, 0, 0, PTHREAD_MUTEX_ERRORCHECK_NP, {0, 0}};
#else
static pthread_mutex_t mark_mutex = PTHREAD_MUTEX_INITIALIZER;
#endif
static pthread_cond_t builder_cv = PTHREAD_COND_INITIALIZER;
void GC_acquire_mark_lock()
{
/*
if (pthread_mutex_lock(&mark_mutex) != 0) {
ABORT("pthread_mutex_lock failed");
}
*/
GC_generic_lock(&mark_mutex);
# ifdef GC_ASSERTIONS
GC_mark_lock_holder = pthread_self();
# endif
}
void GC_release_mark_lock()
{
GC_ASSERT(GC_mark_lock_holder == pthread_self());
# ifdef GC_ASSERTIONS
GC_mark_lock_holder = NO_THREAD;
# endif
if (pthread_mutex_unlock(&mark_mutex) != 0) {
ABORT("pthread_mutex_unlock failed");
}
}
/* Collector must wait for a freelist builders for 2 reasons: */
/* 1) Mark bits may still be getting examined without lock. */
/* 2) Partial free lists referenced only by locals may not be scanned */
/* correctly, e.g. if they contain "pointer-free" objects, since the */
/* free-list link may be ignored. */
void GC_wait_builder()
{
GC_ASSERT(GC_mark_lock_holder == pthread_self());
# ifdef GC_ASSERTIONS
GC_mark_lock_holder = NO_THREAD;
# endif
if (pthread_cond_wait(&builder_cv, &mark_mutex) != 0) {
ABORT("pthread_cond_wait failed");
}
GC_ASSERT(GC_mark_lock_holder == NO_THREAD);
# ifdef GC_ASSERTIONS
GC_mark_lock_holder = pthread_self();
# endif
}
void GC_wait_for_reclaim()
{
GC_acquire_mark_lock();
while (GC_fl_builder_count > 0) {
GC_wait_builder();
}
GC_release_mark_lock();
}
void GC_notify_all_builder()
{
GC_ASSERT(GC_mark_lock_holder == pthread_self());
if (pthread_cond_broadcast(&builder_cv) != 0) {
ABORT("pthread_cond_broadcast failed");
}
}
#endif /* PARALLEL_MARK || THREAD_LOCAL_ALLOC */
#ifdef PARALLEL_MARK
static pthread_cond_t mark_cv = PTHREAD_COND_INITIALIZER;
void GC_wait_marker()
{
GC_ASSERT(GC_mark_lock_holder == pthread_self());
# ifdef GC_ASSERTIONS
GC_mark_lock_holder = NO_THREAD;
# endif
if (pthread_cond_wait(&mark_cv, &mark_mutex) != 0) {
ABORT("pthread_cond_wait failed");
}
GC_ASSERT(GC_mark_lock_holder == NO_THREAD);
# ifdef GC_ASSERTIONS
GC_mark_lock_holder = pthread_self();
# endif
}
void GC_notify_all_marker()
{
if (pthread_cond_broadcast(&mark_cv) != 0) {
ABORT("pthread_cond_broadcast failed");
}
}
#endif /* PARALLEL_MARK */
# endif /* LINUX_THREADS */
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