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Linux: Move __reclaim_stacks into the fork implementation in libc

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As a result, __libc_pthread_init is no longer needed.

Tested-by: Carlos O'Donell <carlos@redhat.com>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
Florian Weimer 2021-05-10 10:31:42 +02:00
parent 8c1c0da3a8
commit 732139dabe
5 changed files with 110 additions and 119 deletions
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1
nptl/Versions
View File

@ -308,7 +308,6 @@ libc {
__libc_cleanup_push_defer;
__libc_dl_error_tsd;
__libc_multiple_threads;
__libc_pthread_init;
__lll_clocklock_elision;
__lll_lock_elision;
__lll_lock_wait;

108
nptl/allocatestack.c
View File

@ -754,111 +754,3 @@ __deallocate_stack (struct pthread *pd)
lll_unlock (GL (dl_stack_cache_lock), LLL_PRIVATE);
}
/* In case of a fork() call the memory allocation in the child will be
the same but only one thread is running. All stacks except that of
the one running thread are not used anymore. We have to recycle
them. */
void
__reclaim_stacks (void)
{
struct pthread *self = (struct pthread *) THREAD_SELF;
/* No locking necessary. The caller is the only stack in use. But
we have to be aware that we might have interrupted a list
operation. */
if (GL (dl_in_flight_stack) != 0)
{
bool add_p = GL (dl_in_flight_stack) & 1;
list_t *elem = (list_t *) (GL (dl_in_flight_stack) & ~(uintptr_t) 1);
if (add_p)
{
/* We always add at the beginning of the list. So in this case we
only need to check the beginning of these lists to see if the
pointers at the head of the list are inconsistent. */
list_t *l = NULL;
if (GL (dl_stack_used).next->prev != &GL (dl_stack_used))
l = &GL (dl_stack_used);
else if (GL (dl_stack_cache).next->prev != &GL (dl_stack_cache))
l = &GL (dl_stack_cache);
if (l != NULL)
{
assert (l->next->prev == elem);
elem->next = l->next;
elem->prev = l;
l->next = elem;
}
}
else
{
/* We can simply always replay the delete operation. */
elem->next->prev = elem->prev;
elem->prev->next = elem->next;
}
GL (dl_in_flight_stack) = 0;
}
/* Mark all stacks except the still running one as free. */
list_t *runp;
list_for_each (runp, &GL (dl_stack_used))
{
struct pthread *curp = list_entry (runp, struct pthread, list);
if (curp != self)
{
/* This marks the stack as free. */
curp->tid = 0;
/* Account for the size of the stack. */
GL (dl_stack_cache_actsize) += curp->stackblock_size;
if (curp->specific_used)
{
/* Clear the thread-specific data. */
memset (curp->specific_1stblock, '\0',
sizeof (curp->specific_1stblock));
curp->specific_used = false;
for (size_t cnt = 1; cnt < PTHREAD_KEY_1STLEVEL_SIZE; ++cnt)
if (curp->specific[cnt] != NULL)
{
memset (curp->specific[cnt], '\0',
sizeof (curp->specific_1stblock));
/* We have allocated the block which we do not
free here so re-set the bit. */
curp->specific_used = true;
}
}
}
}
/* Add the stack of all running threads to the cache. */
list_splice (&GL (dl_stack_used), &GL (dl_stack_cache));
/* Remove the entry for the current thread to from the cache list
and add it to the list of running threads. Which of the two
lists is decided by the user_stack flag. */
list_del (&self->list);
/* Re-initialize the lists for all the threads. */
INIT_LIST_HEAD (&GL (dl_stack_used));
INIT_LIST_HEAD (&GL (dl_stack_user));
if (__glibc_unlikely (THREAD_GETMEM (self, user_stack)))
list_add (&self->list, &GL (dl_stack_user));
else
list_add (&self->list, &GL (dl_stack_used));
/* There is one thread running. */
__nptl_nthreads = 1;
/* Initialize locks. */
GL (dl_stack_cache_lock) = LLL_LOCK_INITIALIZER;
__default_pthread_attr_lock = LLL_LOCK_INITIALIZER;
}

3
nptl/nptl-init.c
View File

@ -172,9 +172,6 @@ __pthread_initialize_minimal_internal (void)
__default_pthread_attr.internal.stacksize = limit.rlim_cur;
__default_pthread_attr.internal.guardsize = GLRO (dl_pagesize);
lll_unlock (__default_pthread_attr_lock, LLL_PRIVATE);
/* Register the fork generation counter with the libc. */
__libc_pthread_init (__reclaim_stacks);
}
strong_alias (__pthread_initialize_minimal_internal,
__pthread_initialize_minimal)

7
nptl/pthreadP.h
View File

@ -333,10 +333,6 @@ extern void __free_tcb (struct pthread *pd) attribute_hidden;
/* Free allocated stack. */
extern void __deallocate_stack (struct pthread *pd) attribute_hidden;
/* Mark all the stacks except for the current one as available. This
function also re-initializes the lock for the stack cache. */
extern void __reclaim_stacks (void) attribute_hidden;
/* Change the permissions of a thread stack. Called from
_dl_make_stacks_executable and pthread_create. */
int
@ -372,9 +368,6 @@ 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;
/* Register the generation counter in the libpthread with the libc. */
extern void __libc_pthread_init (void (*reclaim) (void));
extern size_t __pthread_get_minstack (const pthread_attr_t *attr);
/* Namespace save aliases. */

110
sysdeps/nptl/fork.c
View File

@ -35,6 +35,7 @@
#include <nss/nss_database.h>
#include <unwind-link.h>
#include <sys/single_threaded.h>
#include <list.h>
static void
fresetlockfiles (void)
@ -46,6 +47,106 @@ fresetlockfiles (void)
_IO_lock_init (*((_IO_lock_t *) _IO_iter_file(i)->_lock));
}
/* In case of a fork() call the memory allocation in the child will be
the same but only one thread is running. All stacks except that of
the one running thread are not used anymore. We have to recycle
them. */
static void
reclaim_stacks (void)
{
struct pthread *self = (struct pthread *) THREAD_SELF;
/* No locking necessary. The caller is the only stack in use. But
we have to be aware that we might have interrupted a list
operation. */
if (GL (dl_in_flight_stack) != 0)
{
bool add_p = GL (dl_in_flight_stack) & 1;
list_t *elem = (list_t *) (GL (dl_in_flight_stack) & ~(uintptr_t) 1);
if (add_p)
{
/* We always add at the beginning of the list. So in this case we
only need to check the beginning of these lists to see if the
pointers at the head of the list are inconsistent. */
list_t *l = NULL;
if (GL (dl_stack_used).next->prev != &GL (dl_stack_used))
l = &GL (dl_stack_used);
else if (GL (dl_stack_cache).next->prev != &GL (dl_stack_cache))
l = &GL (dl_stack_cache);
if (l != NULL)
{
assert (l->next->prev == elem);
elem->next = l->next;
elem->prev = l;
l->next = elem;
}
}
else
{
/* We can simply always replay the delete operation. */
elem->next->prev = elem->prev;
elem->prev->next = elem->next;
}
GL (dl_in_flight_stack) = 0;
}
/* Mark all stacks except the still running one as free. */
list_t *runp;
list_for_each (runp, &GL (dl_stack_used))
{
struct pthread *curp = list_entry (runp, struct pthread, list);
if (curp != self)
{
/* This marks the stack as free. */
curp->tid = 0;
/* Account for the size of the stack. */
GL (dl_stack_cache_actsize) += curp->stackblock_size;
if (curp->specific_used)
{
/* Clear the thread-specific data. */
memset (curp->specific_1stblock, '\0',
sizeof (curp->specific_1stblock));
curp->specific_used = false;
for (size_t cnt = 1; cnt < PTHREAD_KEY_1STLEVEL_SIZE; ++cnt)
if (curp->specific[cnt] != NULL)
{
memset (curp->specific[cnt], '\0',
sizeof (curp->specific_1stblock));
/* We have allocated the block which we do not
free here so re-set the bit. */
curp->specific_used = true;
}
}
}
}
/* Add the stack of all running threads to the cache. */
list_splice (&GL (dl_stack_used), &GL (dl_stack_cache));
/* Remove the entry for the current thread to from the cache list
and add it to the list of running threads. Which of the two
lists is decided by the user_stack flag. */
list_del (&self->list);
/* Re-initialize the lists for all the threads. */
INIT_LIST_HEAD (&GL (dl_stack_used));
INIT_LIST_HEAD (&GL (dl_stack_user));
if (__glibc_unlikely (THREAD_GETMEM (self, user_stack)))
list_add (&self->list, &GL (dl_stack_user));
else
list_add (&self->list, &GL (dl_stack_used));
}
pid_t
__libc_fork (void)
@ -112,6 +213,13 @@ __libc_fork (void)
{
__libc_unwind_link_after_fork ();
/* There is one thread running. */
__nptl_nthreads = 1;
/* Initialize thread library locks. */
GL (dl_stack_cache_lock) = LLL_LOCK_INITIALIZER;
__default_pthread_attr_lock = LLL_LOCK_INITIALIZER;
/* Release malloc locks. */
call_function_static_weak (__malloc_fork_unlock_child);
@ -128,6 +236,8 @@ __libc_fork (void)
/* Reset the lock the dynamic loader uses to protect its data. */
__rtld_lock_initialize (GL(dl_load_lock));
reclaim_stacks ();
/* Run the handlers registered for the child. */
__run_fork_handlers (atfork_run_child, multiple_threads);
}