aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorUlrich Drepper <drepper@redhat.com>2003-05-09 03:17:42 +0000
committerUlrich Drepper <drepper@redhat.com>2003-05-09 03:17:42 +0000
commit92d83c725e09dbc76acfedc1cf85a01f9f54452d (patch)
tree039357dd8df0ad0c249d28e098e921ff15fb1eb0
parent29b095a1561f866b995b23621d1e2ee78e473dc4 (diff)
downloadglibc-92d83c725e09dbc76acfedc1cf85a01f9f54452d.tar
glibc-92d83c725e09dbc76acfedc1cf85a01f9f54452d.tar.gz
glibc-92d83c725e09dbc76acfedc1cf85a01f9f54452d.tar.bz2
glibc-92d83c725e09dbc76acfedc1cf85a01f9f54452d.zip
Update.
2003-05-08 Ulrich Drepper <drepper@redhat.com> * malloc/thread-m.h: Remove special handling of thread_atfork if HAVE_register_atfork_malloc is defined.
-rw-r--r--ChangeLog5
-rw-r--r--malloc/thread-m.h19
-rw-r--r--nptl/ChangeLog26
-rw-r--r--nptl/cond-perf.c100
-rw-r--r--nptl/sysdeps/unix/sysv/linux/fork.c105
-rw-r--r--nptl/sysdeps/unix/sysv/linux/fork.h26
-rw-r--r--nptl/sysdeps/unix/sysv/linux/i386/lowlevellock.h30
-rw-r--r--nptl/sysdeps/unix/sysv/linux/libc_pthread_init.c8
-rw-r--r--nptl/sysdeps/unix/sysv/linux/register-atfork.c176
-rw-r--r--nptl/sysdeps/unix/sysv/linux/unregister-atfork.c112
-rw-r--r--nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.h25
11 files changed, 423 insertions, 209 deletions
diff --git a/ChangeLog b/ChangeLog
index 6f46014783..b3f893bde7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2003-05-08 Ulrich Drepper <drepper@redhat.com>
+
+ * malloc/thread-m.h: Remove special handling of thread_atfork if
+ HAVE_register_atfork_malloc is defined.
+
2003-05-07 Andreas Jaeger <aj@suse.de>
* sysdeps/unix/sysv/linux/x86_64/syscall.S: Add DWARF2 unwind
diff --git a/malloc/thread-m.h b/malloc/thread-m.h
index 71409ebc0e..da8bbf36f8 100644
--- a/malloc/thread-m.h
+++ b/malloc/thread-m.h
@@ -77,24 +77,13 @@ extern void *__dso_handle __attribute__ ((__weak__));
#include <fork.h>
-#ifdef HAVE_register_atfork_malloc
-# ifdef SHARED
-# define thread_atfork(prepare, parent, child) \
- __register_atfork_malloc (prepare, parent, child, __dso_handle)
-# else
-# define thread_atfork(prepare, parent, child) \
- __register_atfork_malloc (prepare, parent, child, \
- &__dso_handle == NULL ? NULL : __dso_handle)
-# endif
-#else
-# ifdef SHARED
-# define thread_atfork(prepare, parent, child) \
+#ifdef SHARED
+# define thread_atfork(prepare, parent, child) \
__register_atfork (prepare, parent, child, __dso_handle)
-# else
-# define thread_atfork(prepare, parent, child) \
+#else
+# define thread_atfork(prepare, parent, child) \
__register_atfork (prepare, parent, child, \
&__dso_handle == NULL ? NULL : __dso_handle)
-# endif
#endif
#elif defined(MUTEX_INITIALIZER)
diff --git a/nptl/ChangeLog b/nptl/ChangeLog
index 791d2ece5a..7bd8025850 100644
--- a/nptl/ChangeLog
+++ b/nptl/ChangeLog
@@ -1,3 +1,29 @@
+2003-05-08 Ulrich Drepper <drepper@redhat.com>
+
+ * sysdeps/unix/sysv/linux/fork.c: Complete rewrite of the atfork
+ handler implementation. It is now lockless in fork().
+ * sysdeps/unix/sysv/linux/register-atfork.c: Likewise.
+ * sysdeps/unix/sysv/linux/unregister-atfork.c: Likewise.
+ * sysdeps/unix/sysv/linux/fork.h: Don't include <link.h>. Don't
+ declare the __fork_*_lists.
+ (struct fork_handler): Include pointers to all three functions.
+ Add next, refcntr and need_signal elements.
+ (__fork_handlers): New declaration.
+ (__register_atfork_malloc): Remove declaration.
+ (HAVE_register_atfork_malloc): Remove definition.
+ * sysdeps/unix/sysv/linux/libc_pthread_init.c: Remove
+ __pthread_child_handler variable.
+ (__libc_pthread_init): Use __register_atfork instead of explicitly
+ adding to the list.
+ * sysdeps/unix/sysv/linux/i386/lowlevellock.h: Define lll_futex_wait
+ and lll_futex_wake.
+ * sysdeps/unix/sysv/linux/x86_64/lowlevellock.h: Likewise.
+
+ * unwind.c (unwind_cleanup): Print error message and then abort. This
+ function must never be reached.
+
+ * cond-perf.c: New file.
+
2003-05-05 Ulrich Drepper <drepper@redhat.com>
* sysdeps/i386/tls.h (TLS_INIT_TP): Include \n in error message.
diff --git a/nptl/cond-perf.c b/nptl/cond-perf.c
new file mode 100644
index 0000000000..c3305b391d
--- /dev/null
+++ b/nptl/cond-perf.c
@@ -0,0 +1,100 @@
+#include <pthread.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+static pthread_cond_t cond1 = PTHREAD_COND_INITIALIZER;
+static pthread_mutex_t mut1 = PTHREAD_MUTEX_INITIALIZER;
+
+static pthread_cond_t cond2 = PTHREAD_COND_INITIALIZER;
+static pthread_mutex_t mut2 = PTHREAD_MUTEX_INITIALIZER;
+
+static bool last_round;
+static int ntogo;
+static bool alldone;
+
+
+static void *
+cons (void *arg)
+{
+ pthread_mutex_lock (&mut1);
+
+ do
+ {
+ if (--ntogo == 0)
+ {
+ alldone = true;
+ pthread_cond_signal (&cond2);
+ }
+
+ pthread_cond_wait (&cond1, &mut1);
+ }
+ while (! last_round);
+
+ pthread_mutex_unlock (&mut1);
+
+ return NULL;
+}
+
+
+int
+main (int argc, char *argv[])
+{
+ int opt;
+ int err;
+ int nthreads = 10;
+ int nrounds = 100;
+ bool keeplock = false;
+
+ while ((opt = getopt (argc, argv, "n:r:k")) != -1)
+ switch (opt)
+ {
+ case 'n':
+ nthreads = atol (optarg);
+ break;
+ case 'r':
+ nrounds = atol (optarg);
+ break;
+ case 'k':
+ keeplock = true;
+ break;
+ }
+
+ ntogo = nthreads;
+
+ pthread_t th[nthreads];
+ int i;
+ for (i = 0; i < nthreads; ++i)
+ if ((err = pthread_create (&th[i], NULL, cons, (void *) (long) i)) != 0)
+ printf ("pthread_create: %s\n", strerror (err));
+
+ for (i = 0; i < nrounds; ++i)
+ {
+ pthread_mutex_lock (&mut2);
+ while (! alldone)
+ pthread_cond_wait (&cond2, &mut2);
+ pthread_mutex_unlock (&mut2);
+
+ pthread_mutex_lock (&mut1);
+ if (! keeplock)
+ pthread_mutex_unlock (&mut1);
+
+ ntogo = nthreads;
+ alldone = false;
+ if (i + 1 >= nrounds)
+ last_round = true;
+
+ pthread_cond_broadcast (&cond1);
+
+ if (keeplock)
+ pthread_mutex_unlock (&mut1);
+ }
+
+ for (i = 0; i < nthreads; ++i)
+ if ((err = pthread_join (th[i], NULL)) != 0)
+ printf ("pthread_create: %s\n", strerror (err));
+
+ return 0;
+}
diff --git a/nptl/sysdeps/unix/sysv/linux/fork.c b/nptl/sysdeps/unix/sysv/linux/fork.c
index 94d8995205..8bca6b4ab3 100644
--- a/nptl/sysdeps/unix/sysv/linux/fork.c
+++ b/nptl/sysdeps/unix/sysv/linux/fork.c
@@ -28,15 +28,15 @@
#include <hp-timing.h>
#include <ldsodefs.h>
#include <bits/stdio-lock.h>
+#include <atomic.h>
unsigned long int *__fork_generation_pointer;
-lll_lock_t __fork_lock = LLL_LOCK_INITIALIZER;
-LIST_HEAD (__fork_prepare_list);
-LIST_HEAD (__fork_parent_list);
-LIST_HEAD (__fork_child_list);
+
+/* The single linked list of all currently registered for handlers. */
+struct fork_handler *__fork_handlers;
static void
@@ -53,20 +53,62 @@ pid_t
__libc_fork (void)
{
pid_t pid;
- list_t *runp;
-
- /* Get the lock so that the set of registered handlers is not
- inconsistent or changes beneath us. */
- lll_lock (__fork_lock);
-
- /* Run all the registered preparation handlers. In reverse order. */
- list_for_each_prev (runp, &__fork_prepare_list)
+ struct used_handler
+ {
+ struct fork_handler *handler;
+ struct used_handler *next;
+ } *allp = NULL;
+
+ /* Run all the registered preparation handlers. In reverse order.
+ While doing this we build up a list of all the entries. */
+ struct fork_handler *runp;
+ while ((runp = __fork_handlers) != NULL)
{
- struct fork_handler *curp;
-
- curp = list_entry (runp, struct fork_handler, list);
+ unsigned int oldval = runp->refcntr;
+
+ if (oldval == 0)
+ /* This means some other thread removed the list just after
+ the pointer has been loaded. Try again. Either the list
+ is empty or we can retry it. */
+ continue;
+
+ /* Bump the reference counter. */
+ if (atomic_compare_and_exchange_bool_acq (&__fork_handlers->refcntr,
+ oldval + 1, oldval))
+ /* The value changed, try again. */
+ continue;
+
+ /* We bumped the reference counter for the first entry in the
+ list. That means that none of the following entries will
+ just go away. The unloading code works in the order of the
+ list.
+
+ While executing the registered handlers we are building a
+ list of all the entries so that we can go backward later on. */
+ while (1)
+ {
+ /* Execute the handler if there is one. */
+ if (runp->prepare_handler != NULL)
+ runp->prepare_handler ();
+
+ /* Create a new element for the list. */
+ struct used_handler *newp
+ = (struct used_handler *) alloca (sizeof (*newp));
+ newp->handler = runp;
+ newp->next = allp;
+ allp = newp;
+
+ /* Advance to the next handler. */
+ runp = runp->next;
+ if (runp == NULL)
+ break;
+
+ /* Bump the reference counter for the next entry. */
+ atomic_increment (&runp->refcntr);
+ }
- curp->handler ();
+ /* We are done. */
+ break;
}
_IO_list_lock ();
@@ -107,13 +149,22 @@ __libc_fork (void)
_IO_list_resetlock ();
/* Run the handlers registered for the child. */
- list_for_each (runp, &__fork_child_list)
+ while (allp != NULL)
{
- struct fork_handler *curp;
+ if (allp->handler->child_handler != NULL)
+ allp->handler->child_handler ();
- curp = list_entry (runp, struct fork_handler, list);
+ /* Note that we do not have to wake any possible waiter.
+ This is the only thread in the new process. */
+ --allp->handler->refcntr;
- curp->handler ();
+ /* XXX We could at this point look through the object pool
+ and mark all objects not on the __fork_handlers list as
+ unused. This is necessary in case the fork() happened
+ while another thread called dlclose() and that call had
+ to create a new list. */
+
+ allp = allp->next;
}
/* Initialize the fork lock. */
@@ -127,17 +178,17 @@ __libc_fork (void)
_IO_list_unlock ();
/* Run the handlers registered for the parent. */
- list_for_each (runp, &__fork_parent_list)
+ while (allp != NULL)
{
- struct fork_handler *curp;
+ if (allp->handler->parent_handler != NULL)
+ allp->handler->parent_handler ();
- curp = list_entry (runp, struct fork_handler, list);
+ if (atomic_decrement_and_test (&allp->handler->refcntr)
+ && allp->handler->need_signal)
+ lll_futex_wake (allp->handler->refcntr, 1);
- curp->handler ();
+ allp = allp->next;
}
-
- /* Release the for lock. */
- lll_unlock (__fork_lock);
}
return pid;
diff --git a/nptl/sysdeps/unix/sysv/linux/fork.h b/nptl/sysdeps/unix/sysv/linux/fork.h
index e59ae87964..bcdf6217c1 100644
--- a/nptl/sysdeps/unix/sysv/linux/fork.h
+++ b/nptl/sysdeps/unix/sysv/linux/fork.h
@@ -17,7 +17,6 @@
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
-#include <list.h>
#include <lowlevellock.h>
/* The fork generation counter, defined in libpthread. */
@@ -26,23 +25,24 @@ extern unsigned long int __fork_generation attribute_hidden;
/* Pointer to the fork generation counter in the thread library. */
extern unsigned long int *__fork_generation_pointer attribute_hidden;
-/* Lock to protect handling of fork handlers. */
+/* Lock to protect allocation and deallocation of fork handlers. */
extern lll_lock_t __fork_lock attribute_hidden;
-/* Lists of registered fork handlers. */
-extern list_t __fork_prepare_list attribute_hidden;
-extern list_t __fork_parent_list attribute_hidden;
-extern list_t __fork_child_list attribute_hidden;
-
-
/* Elements of the fork handler lists. */
struct fork_handler
{
- list_t list;
- void (*handler) (void);
+ struct fork_handler *next;
+ void (*prepare_handler) (void);
+ void (*parent_handler) (void);
+ void (*child_handler) (void);
void *dso_handle;
+ unsigned int refcntr;
+ int need_signal;
};
+/* The single linked list of all currently registered for handlers. */
+extern struct fork_handler *__fork_handlers;
+
/* Function to call to unregister fork handlers. */
extern void __unregister_atfork (void *dso_handle) attribute_hidden;
@@ -54,9 +54,3 @@ extern int __register_atfork (void (*__prepare) (void),
void (*__parent) (void),
void (*__child) (void),
void *dso_handle);
-
-extern void __register_atfork_malloc (void (*prepare) (void),
- void (*parent) (void),
- void (*child) (void),
- void *dso_handle) attribute_hidden;
-#define HAVE_register_atfork_malloc
diff --git a/nptl/sysdeps/unix/sysv/linux/i386/lowlevellock.h b/nptl/sysdeps/unix/sysv/linux/i386/lowlevellock.h
index e338cfa811..2318edfcdb 100644
--- a/nptl/sysdeps/unix/sysv/linux/i386/lowlevellock.h
+++ b/nptl/sysdeps/unix/sysv/linux/i386/lowlevellock.h
@@ -41,6 +41,36 @@
#define LLL_MUTEX_LOCK_INITIALIZER (0)
+#define LLL_ENTER_KERNEL "int $0x80\n\t"
+
+#define lll_futex_wait(futex, val) \
+ do { \
+ int __ignore; \
+ register __typeof (val) _val asm ("edx") = (val); \
+ __asm __volatile ("xchgl %2, %%ebx\n\t" \
+ LLL_ENTER_KERNEL \
+ "xchgl %2, %%ebx" \
+ : "=a" (__ignore) \
+ : "0" (SYS_futex), "D" (&futex), "S" (0), \
+ "c" (FUTEX_WAIT), "d" (_val), \
+ "i" (offsetof (tcbhead_t, sysinfo))); \
+ } while (0)
+
+
+#define lll_futex_wake(futex, nr) \
+ do { \
+ int __ignore; \
+ register __typeof (nr) _nr asm ("edx") = (nr); \
+ __asm __volatile ("xchgl %2, %%ebx\n\t" \
+ LLL_ENTER_KERNEL \
+ "xchgl %2, %%ebx" \
+ : "=a" (__ignore) \
+ : "0" (SYS_futex), "D" (&futex), "c" (FUTEX_WAKE), \
+ "d" (_nr), "i" (0), \
+ "i" (offsetof (tcbhead_t, sysinfo))); \
+ } while (0)
+
+
/* Does not preserve %eax and %ecx. */
extern int __lll_mutex_lock_wait (int val, int *__futex)
__attribute ((regparm (2))) attribute_hidden;
diff --git a/nptl/sysdeps/unix/sysv/linux/libc_pthread_init.c b/nptl/sysdeps/unix/sysv/linux/libc_pthread_init.c
index 3891501927..3d1c021819 100644
--- a/nptl/sysdeps/unix/sysv/linux/libc_pthread_init.c
+++ b/nptl/sysdeps/unix/sysv/linux/libc_pthread_init.c
@@ -27,9 +27,6 @@
#include <bits/libc-lock.h>
-struct fork_handler __pthread_child_handler attribute_hidden;
-
-
#ifdef TLS_MULTIPLE_THREADS_IN_TCB
void
#else
@@ -46,10 +43,7 @@ __libc_pthread_init (ptr, reclaim, functions)
__fork_generation_pointer = ptr;
/* Called by a child after fork. */
- __pthread_child_handler.handler = reclaim;
-
- /* The fork handler needed by libpthread. */
- list_add_tail (&__pthread_child_handler.list, &__fork_child_list);
+ __register_atfork (NULL, NULL, reclaim, NULL);
#ifdef SHARED
/* We copy the content of the variable pointed to by the FUNCTIONS
diff --git a/nptl/sysdeps/unix/sysv/linux/register-atfork.c b/nptl/sysdeps/unix/sysv/linux/register-atfork.c
index 6dbc163175..299ae9de29 100644
--- a/nptl/sysdeps/unix/sysv/linux/register-atfork.c
+++ b/nptl/sysdeps/unix/sysv/linux/register-atfork.c
@@ -19,114 +19,92 @@
#include <errno.h>
#include <stdlib.h>
+#include <string.h>
#include "fork.h"
-/* Defined in libc_pthread_init.c. */
-extern struct fork_handler __pthread_child_handler attribute_hidden;
+/* Lock to protect allocation and deallocation of fork handlers. */
+lll_lock_t __fork_lock = LLL_LOCK_INITIALIZER;
-int
-__register_atfork (prepare, parent, child, dso_handle)
- void (*prepare) (void);
- void (*parent) (void);
- void (*child) (void);
- void *dso_handle;
+/* Number of pre-allocated handler entries. */
+#define NHANDLER 48
+
+/* Memory pool for fork handler structures. */
+static struct fork_handler_pool
{
- struct fork_handler *new_prepare = NULL;
- struct fork_handler *new_parent = NULL;
- struct fork_handler *new_child = NULL;
+ struct fork_handler_pool *next;
+ struct fork_handler mem[NHANDLER];
+} fork_handler_pool;
- if (prepare != NULL)
- {
- new_prepare = (struct fork_handler *) malloc (sizeof (*new_prepare));
- if (new_prepare == NULL)
- goto out1;
- new_prepare->handler = prepare;
- new_prepare->dso_handle = dso_handle;
- }
+static struct fork_handler *
+fork_handler_alloc (void)
+{
+ struct fork_handler_pool *runp = &fork_handler_pool;
+ struct fork_handler *result = NULL;
+ unsigned int i;
- if (parent != NULL)
+ do
{
- new_parent = (struct fork_handler *) malloc (sizeof (*new_parent));
- if (new_parent == NULL)
- goto out2;
-
- new_parent->handler = parent;
- new_parent->dso_handle = dso_handle;
+ /* Search for an empty entry. */
+ for (i = 0; i < NHANDLER; ++i)
+ if (runp->mem[i].refcntr == 0)
+ goto found;
}
+ while ((runp = runp->next) != NULL);
- if (child != NULL)
+ /* We have to allocate a new entry. */
+ runp = (struct fork_handler_pool *) calloc (1, sizeof (*runp));
+ if (runp != NULL)
{
- new_child = (struct fork_handler *) malloc (sizeof (*new_child));
- if (new_child == NULL)
- {
- free (new_parent);
- out2:
- free (new_prepare);
- out1:
- return errno;
- }
-
- new_child->handler = child;
- new_child->dso_handle = dso_handle;
+ /* Enqueue the new memory pool into the list. */
+ runp->next = fork_handler_pool.next;
+ fork_handler_pool.next = runp;
+
+ /* We use the last entry on the page. This means when we start
+ searching from the front the next time we will find the first
+ entry unused. */
+ i = NHANDLER - 1;
+
+ found:
+ result = &runp->mem[i];
+ result->refcntr = 1;
+ result->need_signal = 0;
}
- /* Get the lock to not conflict with running forks. */
- lll_lock (__fork_lock);
-
- /* Now that we have all the handlers allocate enqueue them. */
- if (new_prepare != NULL)
- list_add_tail (&new_prepare->list, &__fork_prepare_list);
- if (new_parent != NULL)
- list_add_tail (&new_parent->list, &__fork_parent_list);
- if (new_child != NULL)
- list_add_tail (&new_child->list, &__fork_child_list);
-
- /* Release the lock. */
- lll_unlock (__fork_lock);
-
- return 0;
+ return result;
}
-/* Three static memory blocks used when registering malloc. */
-static struct fork_handler malloc_prepare;
-static struct fork_handler malloc_parent;
-static struct fork_handler malloc_child;
-
-
-void
-attribute_hidden
-__register_atfork_malloc (prepare, parent, child, dso_handle)
+int
+__register_atfork (prepare, parent, child, dso_handle)
void (*prepare) (void);
void (*parent) (void);
void (*child) (void);
void *dso_handle;
{
- /* Pre-fork handler. */
- malloc_prepare.handler = prepare;
- malloc_prepare.dso_handle = dso_handle;
-
- /* Parent handler. */
- malloc_parent.handler = parent;
- malloc_parent.dso_handle = dso_handle;
-
- /* Child handler. */
- malloc_child.handler = child;
- malloc_child.dso_handle = dso_handle;
-
- /* Get the lock to not conflict with running forks. */
+ /* Get the lock to not conflict with other allocations. */
lll_lock (__fork_lock);
- /* Now that we have all the handlers allocate enqueue them. */
- list_add_tail (&malloc_prepare.list, &__fork_prepare_list);
- list_add_tail (&malloc_parent.list, &__fork_parent_list);
- list_add_tail (&malloc_child.list, &__fork_child_list);
+ struct fork_handler *newp = fork_handler_alloc ();
+
+ if (newp != NULL)
+ {
+ /* Initialize the new record. */
+ newp->prepare_handler = prepare;
+ newp->parent_handler = parent;
+ newp->child_handler = child;
+ newp->dso_handle = dso_handle;
+
+ newp->next = __fork_handlers;
+ __fork_handlers = newp;
+ }
/* Release the lock. */
lll_unlock (__fork_lock);
+
+ return newp == NULL ? ENOMEM : 0;
}
@@ -135,36 +113,22 @@ libc_freeres_fn (free_mem)
/* Get the lock to not conflict with running forks. */
lll_lock (__fork_lock);
- list_t *runp;
- list_t *prevp;
-
- list_for_each_prev_safe (runp, prevp, &__fork_prepare_list)
- {
- list_del (runp);
+ /* No more fork handlers. */
+ __fork_handlers = NULL;
- struct fork_handler *p = list_entry (runp, struct fork_handler, list);
- if (p != &malloc_prepare)
- free (p);
- }
+ /* Free eventually alloated memory blocks for the object pool. */
+ struct fork_handler_pool *runp = fork_handler_pool.next;
- list_for_each_prev_safe (runp, prevp, &__fork_parent_list)
- {
- list_del (runp);
+ memset (&fork_handler_pool, '\0', sizeof (fork_handler_pool));
- struct fork_handler *p = list_entry (runp, struct fork_handler, list);
- if (p != &malloc_parent)
- free (p);
- }
+ /* Release the lock. */
+ lll_unlock (__fork_lock);
- list_for_each_prev_safe (runp, prevp, &__fork_child_list)
+ /* We can free the memory after releasing the lock. */
+ while (runp != NULL)
{
- list_del (runp);
-
- struct fork_handler *p = list_entry (runp, struct fork_handler, list);
- if (p != &__pthread_child_handler && p != &malloc_child)
- free (p);
+ struct fork_handler_pool *oldp;
+ runp = runp->next;
+ free (oldp);
}
-
- /* Release the lock. */
- lll_unlock (__fork_lock);
}
diff --git a/nptl/sysdeps/unix/sysv/linux/unregister-atfork.c b/nptl/sysdeps/unix/sysv/linux/unregister-atfork.c
index e9eb1918f6..ac4b3c5d4c 100644
--- a/nptl/sysdeps/unix/sysv/linux/unregister-atfork.c
+++ b/nptl/sysdeps/unix/sysv/linux/unregister-atfork.c
@@ -20,56 +20,92 @@
#include <errno.h>
#include <stdlib.h>
#include "fork.h"
-
-
-/* Defined in libc_pthread_init.c. */
-extern struct fork_handler __pthread_child_handler attribute_hidden;
-/* Three static memory blocks used when registering malloc. */
-static struct fork_handler malloc_prepare;
-static struct fork_handler malloc_parent;
-static struct fork_handler malloc_child;
+#include <atomic.h>
void
__unregister_atfork (dso_handle)
void *dso_handle;
{
- /* Get the lock to not conflict with running forks. */
- lll_lock (__fork_lock);
-
- list_t *runp;
- list_t *prevp;
-
- list_for_each_prev_safe (runp, prevp, &__fork_prepare_list)
- if (list_entry (runp, struct fork_handler, list)->dso_handle == dso_handle)
+ /* Check whether there is any entry in the list which we have to
+ remove. It is likely that this is not the case so don't bother
+ getting the lock.
+
+ We do not worry about other threads adding entries for this DSO
+ right this moment. If this happens this is a race and we can do
+ whatever we please. The program will crash anyway seen. */
+ struct fork_handler *runp = __fork_handlers;
+ struct fork_handler *lastp = NULL;
+
+ while (runp != NULL)
+ if (runp->dso_handle == dso_handle)
+ break;
+ else
{
- list_del (runp);
-
- struct fork_handler *p = list_entry (runp, struct fork_handler, list);
- if (p != &malloc_prepare)
- free (p);
+ lastp = runp;
+ runp = runp->next;
}
- list_for_each_prev_safe (runp, prevp, &__fork_parent_list)
- if (list_entry (runp, struct fork_handler, list)->dso_handle == dso_handle)
- {
- list_del (runp);
+ if (runp == NULL)
+ /* Nothing to do. */
+ return;
- struct fork_handler *p = list_entry (runp, struct fork_handler, list);
- if (p != &malloc_parent)
- free (p);
- }
-
- list_for_each_prev_safe (runp, prevp, &__fork_child_list)
- if (list_entry (runp, struct fork_handler, list)->dso_handle == dso_handle)
- {
- list_del (runp);
+ /* Get the lock to not conflict with additions or deletions. Note
+ that there couldn't have been another thread deleting something.
+ The __unregister_atfork function is only called from the
+ dlclose() code which itself serializes the operations. */
+ lll_lock (__fork_lock);
- struct fork_handler *p = list_entry (runp, struct fork_handler, list);
- if (p != &__pthread_child_handler && p != &malloc_child)
- free (p);
- }
+ /* We have to create a new list with all the entries we don't remove. */
+ struct deleted_handler
+ {
+ struct fork_handler *handler;
+ struct deleted_handler *next;
+ } *deleted = NULL;
+
+ /* Remove the entries for the DSO which is unloaded from the list.
+ It's a single linked list so readers are. */
+ do
+ {
+ if (runp->dso_handle == dso_handle)
+ {
+ if (lastp == NULL)
+ __fork_handlers = runp->next;
+ else
+ lastp->next = runp->next;
+
+ /* We cannot overwrite the ->next element now. Put the deleted
+ entries in a separate list. */
+ struct deleted_handler *newp = alloca (sizeof (*newp));
+ newp->handler = runp;
+ newp->next = deleted;
+ deleted = newp;
+ }
+ else
+ lastp = runp;
+
+ runp = runp->next;
+ }
+ while (runp != NULL);
/* Release the lock. */
lll_unlock (__fork_lock);
+
+ /* Walk the list of all entries which have to be deleted. */
+ while (deleted != NULL)
+ {
+ /* We need to be informed by possible current users. */
+ deleted->handler->need_signal = 1;
+ /* Make sure this gets written out first. */
+ atomic_write_barrier ();
+
+ /* Decrement the reference counter. If it does not reach zero
+ wait for the last user. */
+ atomic_decrement (&deleted->handler->refcntr);
+ unsigned int val;
+ while ((val = deleted->handler->refcntr) != 0)
+ lll_futex_wait (deleted->handler->refcntr, val);
+
+ deleted = deleted->next;
+ }
}
diff --git a/nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.h b/nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.h
index b54ebbfca4..8e1742b671 100644
--- a/nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.h
+++ b/nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.h
@@ -41,6 +41,31 @@
#define LLL_MUTEX_LOCK_INITIALIZER (0)
+#define lll_futex_wait(futex, val) \
+ do { \
+ int __ignore; \
+ register __typeof (val) _val asm ("edx") = (val); \
+ __asm __volatile ("xorq %%r10, %%r10\n\t" \
+ "syscall" \
+ : "=a" (__ignore) \
+ : "0" (SYS_futex), "D" (&futex), "S" (FUTEX_WAIT), \
+ "d" (_val) \
+ : "memory", "cc", "r10", "r11", "cx"); \
+ } while (0)
+
+
+#define lll_futex_wake(futex, nr) \
+ do { \
+ int __ignore; \
+ register __typeof (nr) _nr asm ("edx") = (nr); \
+ __asm __volatile ("syscall" \
+ : "=a" (__ignore) \
+ : "0" (SYS_futex), "D" (&futex), "S" (FUTEX_WAKE), \
+ "d" (_nr) \
+ : "memory", "cc", "r10", "r11", "cx"); \
+ } while (0)
+
+
/* Does not preserve %eax and %ecx. */
extern int __lll_mutex_lock_wait (int *__futex, int __val) attribute_hidden;
/* Does not preserver %eax, %ecx, and %edx. */