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linux: Do not spawn a new thread for SIGEV_THREAD (BZ 30558)

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This commit is contained in:
Adhemerval Zanella 2023-06-19 14:11:58 -03:00
parent 99f9ae4ed0
commit 76d0104ced
11 changed files with 281 additions and 377 deletions
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3
nptl/descr.h
View File

@ -408,6 +408,9 @@ struct pthread
/* rseq area registered with the kernel. */
struct rseq rseq_area;
/* POSIX per-process timer. */
int timerid;
/* This member must be last. */
char end_padding[];

1
rt/Makefile
View File

@ -99,6 +99,7 @@ include ../Rules
CFLAGS-aio_suspend.c += -fexceptions
CFLAGS-mq_timedreceive.c += -fexceptions -fasynchronous-unwind-tables
CFLAGS-mq_timedsend.c += -fexceptions -fasynchronous-unwind-tables
CFLAGS-timer_create.c += -fexceptions -fasynchronous-unwind-tables
LDFLAGS-rt.so = -Wl,--enable-new-dtags,-z,nodelete

59
rt/tst-timer-sigmask.c
View File

@ -29,29 +29,43 @@
static pthread_barrier_t barrier;
static void
__attribute_used__
cl (void *arg)
{
xpthread_barrier_wait (&barrier);
}
static void
thread_handler (union sigval sv)
{
sigset_t ss;
sigprocmask (SIG_BLOCK, NULL, &ss);
if (test_verbose > 0)
printf ("%s: blocked signal mask = { ", __func__);
for (int sig = 1; sig < NSIG; sig++)
{
/* POSIX timers threads created to handle SIGEV_THREAD block all
signals except SIGKILL, SIGSTOP and glibc internals ones. */
if (sigismember (&ss, sig))
{
TEST_VERIFY (sig != SIGKILL && sig != SIGSTOP);
TEST_VERIFY (!is_internal_signal (sig));
}
if (test_verbose && sigismember (&ss, sig))
printf ("%d, ", sig);
}
if (test_verbose > 0)
printf ("}\n");
/* POSIX timers threads created to handle SIGEV_THREAD block all
signals except SIGKILL, SIGSTOP, and SIGSETXID. */
sigset_t expected_set = {
.__val = {[0 ... __NSIG_WORDS-1 ] = -1 }
};
__sigdelset (&expected_set, SIGSETXID);
__sigdelset (&expected_set, SIGKILL);
__sigdelset (&expected_set, SIGSTOP);
xpthread_barrier_wait (&barrier);
sigset_t ss;
sigprocmask (SIG_SETMASK, NULL, &ss);
TEST_COMPARE_BLOB (&ss.__val, __NSIG_BYTES, &expected_set, __NSIG_BYTES);
/* Unblock some signals, the signal mask should be reset by the timer_create
helper thread. */
{
sigset_t toset;
sigemptyset (&toset);
sigaddset (&toset, SIGHUP);
sigaddset (&toset, SIGILL);
sigprocmask (SIG_UNBLOCK, &toset, NULL);
}
pthread_cleanup_push (cl, NULL);
pthread_exit (NULL);
pthread_cleanup_pop (0);
}
static int
@ -66,11 +80,12 @@ do_test (void)
xpthread_barrier_init (&barrier, NULL, 2);
struct itimerspec trigger = { 0 };
trigger.it_value.tv_nsec = 1000000;
struct itimerspec trigger = { { 0, 1000000 }, { 0, 1000000 } };
TEST_COMPARE (timer_settime (timerid, 0, &trigger, NULL), 0);
xpthread_barrier_wait (&barrier);
enum { TIMERS_TO_CHECK = 2 };
for (int i = 0; i < TIMERS_TO_CHECK; i++)
xpthread_barrier_wait (&barrier);
return 0;
}

2
sysdeps/nptl/fork.h
View File

@ -20,7 +20,6 @@
#define _FORK_H
#include <assert.h>
#include <kernel-posix-timers.h>
#include <ldsodefs.h>
#include <list.h>
#include <mqueue.h>
@ -45,7 +44,6 @@ fork_system_setup_after_fork (void)
__default_pthread_attr_lock = LLL_LOCK_INITIALIZER;
call_function_static_weak (__mq_notify_fork_subprocess);
call_function_static_weak (__timer_fork_subprocess);
}
/* In case of a fork() call the memory allocation in the child will be

44
sysdeps/pthread/tst-cancel28.c
View File

@ -28,48 +28,64 @@
#include <support/xthread.h>
static pthread_barrier_t barrier;
static pthread_t timer_thread;
#define VALUE1_INITIAL 0
static __thread unsigned int value1 = VALUE1_INITIAL;
#define VALUE2_INITIAL 0xdeadbeef
static __thread unsigned int value2 = VALUE2_INITIAL;
static int cl_called = 0;
static void
cl (void *arg)
{
xpthread_barrier_wait (&barrier);
cl_called++;
xpthread_barrier_wait (&barrier); /* 1 */
}
static void
thread_handler (union sigval sv)
{
timer_thread = pthread_self ();
/* Check if thread state is correctly reset after a pthread_exit. */
TEST_COMPARE (value1, VALUE1_INITIAL);
TEST_COMPARE (value2, VALUE2_INITIAL);
xpthread_barrier_wait (&barrier);
value1 = VALUE2_INITIAL;
value2 = VALUE1_INITIAL;
xpthread_barrier_wait (&barrier); /* 0 */
pthread_cleanup_push (cl, NULL);
while (1)
clock_nanosleep (CLOCK_REALTIME, 0, &(struct timespec) { 1, 0 }, NULL);
pthread_exit (NULL);
pthread_cleanup_pop (0);
}
static int
do_test (void)
{
struct sigevent sev = { 0 };
sev.sigev_notify = SIGEV_THREAD;
sev.sigev_notify_function = &thread_handler;
struct sigevent sev = {
.sigev_notify = SIGEV_THREAD,
.sigev_notify_function = &thread_handler,
};
timer_t timerid;
TEST_COMPARE (timer_create (CLOCK_REALTIME, &sev, &timerid), 0);
xpthread_barrier_init (&barrier, NULL, 2);
struct itimerspec trigger = { 0 };
trigger.it_value.tv_nsec = 1000000;
struct itimerspec trigger = { { 0, 1000000 }, { 0, 1000000 } };
TEST_COMPARE (timer_settime (timerid, 0, &trigger, NULL), 0);
xpthread_barrier_wait (&barrier);
enum { TIMERS_TO_CHECK = 4 };
for (int i = 0; i < TIMERS_TO_CHECK; i++)
{
/* Check the thread local values. */
xpthread_barrier_wait (&barrier); /* 0 */
xpthread_cancel (timer_thread);
xpthread_barrier_wait (&barrier); /* 1 */
}
xpthread_barrier_wait (&barrier);
TEST_COMPARE (cl_called, TIMERS_TO_CHECK);
return 0;
}

8
sysdeps/unix/sysv/linux/internal-signals.h
View File

@ -99,12 +99,4 @@ static const sigset_t sigtimer_set = {
}
};
/* Unblock only SIGTIMER. */
static inline void
signal_unblock_sigtimer (void)
{
INTERNAL_SYSCALL_CALL (rt_sigprocmask, SIG_UNBLOCK, &sigtimer_set, NULL,
__NSIG_BYTES);
}
#endif

2
sysdeps/unix/sysv/linux/kernel-posix-cpu-timers.h
View File

@ -8,6 +8,8 @@
- A clockid is invalid if bits 2, 1, and 0 are all set.
*/
#include <time.h>
#define CPUCLOCK_PID(clock) ((pid_t) ~((clock) >> 3))
#define CPUCLOCK_PERTHREAD(clock) \
(((clock) & (clockid_t) CPUCLOCK_PERTHREAD_MASK) != 0)

54
sysdeps/unix/sysv/linux/kernel-posix-timers.h
View File

@ -19,29 +19,7 @@
#include <setjmp.h>
#include <signal.h>
#include <sys/types.h>
/* Nonzero if the system calls are not available. */
extern int __no_posix_timers attribute_hidden;
/* Callback to start helper thread. */
extern void __timer_start_helper_thread (void) attribute_hidden;
/* Control variable for helper thread creation. */
extern pthread_once_t __timer_helper_once attribute_hidden;
/* Called from fork so that the new subprocess re-creates the
notification thread if necessary. */
void __timer_fork_subprocess (void) attribute_hidden;
/* TID of the helper thread. */
extern pid_t __timer_helper_tid attribute_hidden;
/* List of active SIGEV_THREAD timers. */
extern struct timer *__timer_active_sigev_thread attribute_hidden;
/* Lock for __timer_active_sigev_thread. */
extern pthread_mutex_t __timer_active_sigev_thread_lock attribute_hidden;
#include <nptl/descr.h>
extern __typeof (timer_create) __timer_create;
libc_hidden_proto (__timer_create)
@ -53,25 +31,9 @@ libc_hidden_proto (__timer_getoverrun)
/* Type of timers in the kernel. */
typedef int kernel_timer_t;
/* Internal representation of SIGEV_THREAD timer. */
struct timer
{
kernel_timer_t ktimerid;
void (*thrfunc) (sigval_t);
sigval_t sival;
pthread_attr_t attr;
/* Next element in list of active SIGEV_THREAD timers. */
struct timer *next;
};
/* For !SIGEV_THREAD, the resulting 'timer_t' is the returned kernel timer
identifier (kernel_timer_t), while for SIGEV_THREAD it uses the fact malloc
returns at least _Alignof (max_align_t) pointers plus that valid
kernel_timer_t are always positive to set the MSB bit of the returned
'timer_t' to indicate the timer handles a SIGEV_THREAD. */
identifier (kernel_timer_t), while for SIGEV_THREAD it assumes the
pthread_t is always 8-byte aligned. */
static inline timer_t
kernel_timer_to_timerid (kernel_timer_t ktimerid)
@ -80,7 +42,7 @@ kernel_timer_to_timerid (kernel_timer_t ktimerid)
}
static inline timer_t
timer_to_timerid (struct timer *ptr)
pthread_to_timerid (pthread_t ptr)
{
return (timer_t) (INTPTR_MIN | (uintptr_t) ptr >> 1);
}
@ -91,17 +53,17 @@ timer_is_sigev_thread (timer_t timerid)
return (intptr_t) timerid < 0;
}
static inline struct timer *
timerid_to_timer (timer_t timerid)
static inline struct pthread *
timerid_to_pthread (timer_t timerid)
{
return (struct timer *)((uintptr_t) timerid << 1);
return (struct pthread *)((uintptr_t) timerid << 1);
}
static inline kernel_timer_t
timerid_to_kernel_timer (timer_t timerid)
{
if (timer_is_sigev_thread (timerid))
return timerid_to_timer (timerid)->ktimerid;
return timerid_to_pthread (timerid)->timerid;
else
return (kernel_timer_t) ((uintptr_t) timerid);
}

290
sysdeps/unix/sysv/linux/timer_create.c
View File

@ -15,46 +15,198 @@
License along with the GNU C Library; see the file COPYING.LIB. If
not, see <https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <pthread.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <sysdep.h>
#include <internaltypes.h>
#include <jmpbuf-unwind.h>
#include <kernel-posix-cpu-timers.h>
#include <kernel-posix-timers.h>
#include <ldsodefs.h>
#include <libc-internal.h>
#include <libc-lock.h>
#include <pthreadP.h>
#include "kernel-posix-timers.h"
#include "kernel-posix-cpu-timers.h"
#include <shlib-compat.h>
struct timer_helper_thread_args_t
{
/* The barrier is used to synchronize the arguments copy from timer_created
to the timer thread. */
pthread_barrier_t b;
struct sigevent *evp;
};
extern _Noreturn void __longjmp_cancel (__jmp_buf __env, int __val)
attribute_hidden;
struct cleanup_args_t
{
struct pthread_unwind_buf *cleanup_jmp_buf;
jmp_buf jb;
};
static void
timer_helper_thread_cleanup (void *arg)
{
struct pthread *self = THREAD_SELF;
/* Call destructors for the thread_local TLS variables. */
#ifndef SHARED
if (&__call_tls_dtors != NULL)
#endif
__call_tls_dtors ();
/* Run the destructor for the thread-local data. */
__nptl_deallocate_tsd ();
/* Clean up any state libc stored in thread-local variables. */
__libc_thread_freeres ();
/* Reset internal TCB state. */
struct cleanup_args_t *args = arg;
self->cleanup_jmp_buf = args->cleanup_jmp_buf;
self->cleanup_jmp_buf->priv.data.prev = NULL;
self->cleanup_jmp_buf->priv.data.cleanup = NULL;
self->cleanup_jmp_buf->priv.data.canceltype = 0;
self->cleanup = NULL;
self->exc = (struct _Unwind_Exception) { 0 };
self->cancelhandling = 0;
self->nextevent = NULL;
/* Re-initialize the TLS. */
_dl_allocate_tls_init (TLS_TPADJ (self), true);
internal_sigset_t ss;
internal_sigfillset (&ss);
internal_sigdelset (&ss, SIGSETXID);
internal_sigprocmask (SIG_SETMASK, &ss, NULL);
/* There is no need to perform any additional cleanup by the frames. */
struct __jmp_buf_tag *env = args->jb;
__longjmp (env[0].__jmpbuf, 1);
}
static void *
timer_helper_thread (void *arg)
{
struct pthread *self = THREAD_SELF;
struct timer_helper_thread_args_t *args = arg;
void (*thrfunc) (sigval_t) = args->evp->sigev_notify_function;
sigval_t sival = args->evp->sigev_value;
__pthread_barrier_wait (&args->b);
/* timer_create failed. */
if (self->timerid < 0)
return 0;
struct cleanup_args_t clargs = {
.cleanup_jmp_buf = self->cleanup_jmp_buf
};
while (1)
{
siginfo_t si;
while (__sigwaitinfo (&sigtimer_set, &si) < 0) {};
if (si.si_code == SI_TIMER && !setjmp (clargs.jb))
{
pthread_cleanup_push (timer_helper_thread_cleanup, &clargs);
thrfunc (sival);
pthread_cleanup_pop (0);
}
/* timer_delete will set the MSB and signal the thread. */
if (atomic_load_relaxed (&self->timerid) < 0)
break;
}
/* Clear the MSB bit set by timer_delete. */
INTERNAL_SYSCALL_CALL (timer_delete, self->timerid & INT_MAX);
return NULL;
}
static int
timer_create_sigev_thread (clockid_t syscall_clockid, struct sigevent *evp,
timer_t *timerid)
{
int ret = -1;
pthread_attr_t attr;
if (evp->sigev_notify_attributes != NULL)
__pthread_attr_copy (&attr, evp->sigev_notify_attributes);
else
__pthread_attr_init (&attr);
__pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);
/* Block all signals in the helper thread but SIGSETXID. */
sigset_t ss;
__sigfillset (&ss);
__sigdelset (&ss, SIGSETXID);
ret = __pthread_attr_setsigmask_internal (&attr, &ss);
if (ret != 0)
goto out;
struct timer_helper_thread_args_t args;
__pthread_barrier_init (&args.b, NULL, 2);
args.evp = evp;
pthread_t th;
ret = __pthread_create (&th, &attr, timer_helper_thread, &args);
if (ret != 0)
{
__set_errno (ret);
goto out;
}
struct sigevent kevp = {
.sigev_value.sival_ptr = NULL,
.sigev_signo = SIGTIMER,
.sigev_notify = SIGEV_THREAD_ID,
._sigev_un = { ._pad = { [0] = ((struct pthread *)th)->tid } }
};
struct pthread *pthr = (struct pthread *)th;
kernel_timer_t ktimerid;
if (INLINE_SYSCALL_CALL (timer_create, syscall_clockid, &kevp, &ktimerid) < 0)
pthr->timerid = -1;
pthr->timerid = ktimerid;
/* Signal the thread to continue execution after it copies the arguments
or exit if the timer can not be created. */
__pthread_barrier_wait (&args.b);
if (timerid >= 0)
*timerid = pthread_to_timerid (th);
ret = 0;
out:
if (&attr != evp->sigev_notify_attributes)
__pthread_attr_destroy (&attr);
return ret;
}
int
___timer_create (clockid_t clock_id, struct sigevent *evp, timer_t *timerid)
{
{
clockid_t syscall_clockid = (clock_id == CLOCK_PROCESS_CPUTIME_ID
? PROCESS_CLOCK
: clock_id == CLOCK_THREAD_CPUTIME_ID
? THREAD_CLOCK
: clock_id);
clockid_t syscall_clockid = (clock_id == CLOCK_PROCESS_CPUTIME_ID
? PROCESS_CLOCK
: clock_id == CLOCK_THREAD_CPUTIME_ID
? THREAD_CLOCK
: clock_id);
/* If the user wants notification via a thread we need to handle
this special. */
if (evp == NULL
|| __builtin_expect (evp->sigev_notify != SIGEV_THREAD, 1))
switch (evp != NULL ? evp->sigev_notify : SIGEV_SIGNAL)
{
case SIGEV_NONE:
case SIGEV_SIGNAL:
case SIGEV_THREAD_ID:
{
struct sigevent local_evp;
struct sigevent kevp;
if (evp == NULL)
{
/* The kernel has to pass up the timer ID which is a
userlevel object. Therefore we cannot leave it up to
the kernel to determine it. */
local_evp.sigev_notify = SIGEV_SIGNAL;
local_evp.sigev_signo = SIGALRM;
local_evp.sigev_value.sival_ptr = NULL;
evp = &local_evp;
kevp.sigev_notify = SIGEV_SIGNAL;
kevp.sigev_signo = SIGALRM;
kevp.sigev_value.sival_ptr = NULL;
evp = &kevp;
}
kernel_timer_t ktimerid;
@ -64,75 +216,15 @@ ___timer_create (clockid_t clock_id, struct sigevent *evp, timer_t *timerid)
*timerid = kernel_timer_to_timerid (ktimerid);
}
else
{
/* Create the helper thread. */
__pthread_once (&__timer_helper_once, __timer_start_helper_thread);
if (__timer_helper_tid == 0)
{
/* No resources to start the helper thread. */
__set_errno (EAGAIN);
return -1;
}
struct timer *newp = malloc (sizeof (struct timer));
if (newp == NULL)
return -1;
/* Copy the thread parameters the user provided. */
newp->sival = evp->sigev_value;
newp->thrfunc = evp->sigev_notify_function;
/* We cannot simply copy the thread attributes since the
implementation might keep internal information for
each instance. */
__pthread_attr_init (&newp->attr);
if (evp->sigev_notify_attributes != NULL)
{
struct pthread_attr *nattr;
struct pthread_attr *oattr;
nattr = (struct pthread_attr *) &newp->attr;
oattr = (struct pthread_attr *) evp->sigev_notify_attributes;
nattr->schedparam = oattr->schedparam;
nattr->schedpolicy = oattr->schedpolicy;
nattr->flags = oattr->flags;
nattr->guardsize = oattr->guardsize;
nattr->stackaddr = oattr->stackaddr;
nattr->stacksize = oattr->stacksize;
}
/* In any case set the detach flag. */
__pthread_attr_setdetachstate (&newp->attr, PTHREAD_CREATE_DETACHED);
/* Create the event structure for the kernel timer. */
struct sigevent sev =
{ .sigev_value.sival_ptr = newp,
.sigev_signo = SIGTIMER,
.sigev_notify = SIGEV_SIGNAL | SIGEV_THREAD_ID,
._sigev_un = { ._pad = { [0] = __timer_helper_tid } } };
/* Create the timer. */
int res;
res = INTERNAL_SYSCALL_CALL (timer_create, syscall_clockid, &sev,
&newp->ktimerid);
if (INTERNAL_SYSCALL_ERROR_P (res))
{
free (newp);
__set_errno (INTERNAL_SYSCALL_ERRNO (res));
return -1;
}
/* Add to the queue of active timers with thread delivery. */
__pthread_mutex_lock (&__timer_active_sigev_thread_lock);
newp->next = __timer_active_sigev_thread;
__timer_active_sigev_thread = newp;
__pthread_mutex_unlock (&__timer_active_sigev_thread_lock);
*timerid = timer_to_timerid (newp);
}
}
break;
case SIGEV_THREAD:
if (timer_create_sigev_thread (syscall_clockid, evp, timerid) < 0)
return -1;
break;
default:
__set_errno (EINVAL);
return -1;
}
return 0;
}

40
sysdeps/unix/sysv/linux/timer_delete.c
View File

@ -26,42 +26,18 @@
int
___timer_delete (timer_t timerid)
{
kernel_timer_t ktimerid = timerid_to_kernel_timer (timerid);
int res = INLINE_SYSCALL_CALL (timer_delete, ktimerid);
if (res == 0)
if (timer_is_sigev_thread (timerid))
{
if (timer_is_sigev_thread (timerid))
{
struct timer *kt = timerid_to_timer (timerid);
/* Remove the timer from the list. */
__pthread_mutex_lock (&__timer_active_sigev_thread_lock);
if (__timer_active_sigev_thread == kt)
__timer_active_sigev_thread = kt->next;
else
{
struct timer *prevp = __timer_active_sigev_thread;
while (prevp->next != NULL)
if (prevp->next == kt)
{
prevp->next = kt->next;
break;
}
else
prevp = prevp->next;
}
__pthread_mutex_unlock (&__timer_active_sigev_thread_lock);
free (kt);
}
struct pthread *th = timerid_to_pthread (timerid);
/* The helper thread itself will be responsible to call the
timer_delete syscall. */
kernel_timer_t timerid = atomic_load_relaxed (&th->timerid);
atomic_store_relaxed (&th->timerid, timerid | INT_MIN);
__pthread_kill_internal ((pthread_t) th, SIGTIMER);
return 0;
}
/* The kernel timer is not known or something else bad happened.
Return the error. */
return -1;
return INLINE_SYSCALL_CALL (timer_delete, timerid);
}
versioned_symbol (libc, ___timer_delete, timer_delete, GLIBC_2_34);
libc_hidden_ver (___timer_delete, __timer_delete)

155
sysdeps/unix/sysv/linux/timer_routines.c
View File

@ -1,154 +1 @@
/* Copyright (C) 2003-2023 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1 of the
License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; see the file COPYING.LIB. If
not, see <https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <setjmp.h>
#include <signal.h>
#include <stdbool.h>
#include <sysdep-cancel.h>
#include <pthreadP.h>
#include "kernel-posix-timers.h"
/* List of active SIGEV_THREAD timers. */
struct timer *__timer_active_sigev_thread;
/* Lock for _timer_active_sigev_thread. */
pthread_mutex_t __timer_active_sigev_thread_lock = PTHREAD_MUTEX_INITIALIZER;
struct thread_start_data
{
void (*thrfunc) (sigval_t);
sigval_t sival;
};
/* Helper thread to call the user-provided function. */
static void *
timer_sigev_thread (void *arg)
{
signal_unblock_sigtimer ();
struct thread_start_data *td = (struct thread_start_data *) arg;
void (*thrfunc) (sigval_t) = td->thrfunc;
sigval_t sival = td->sival;
/* The TD object was allocated in timer_helper_thread. */
free (td);
/* Call the user-provided function. */
thrfunc (sival);
return NULL;
}
/* Helper function to support starting threads for SIGEV_THREAD. */
static _Noreturn void *
timer_helper_thread (void *arg)
{
/* Endless loop of waiting for signals. The loop is only ended when
the thread is canceled. */
while (1)
{
siginfo_t si;
while (__sigwaitinfo (&sigtimer_set, &si) < 0);
if (si.si_code == SI_TIMER)
{
struct timer *tk = (struct timer *) si.si_ptr;
/* Check the timer is still used and will not go away
while we are reading the values here. */
__pthread_mutex_lock (&__timer_active_sigev_thread_lock);
struct timer *runp = __timer_active_sigev_thread;
while (runp != NULL)
if (runp == tk)
break;
else
runp = runp->next;
if (runp != NULL)
{
struct thread_start_data *td = malloc (sizeof (*td));
/* There is not much we can do if the allocation fails. */
if (td != NULL)
{
/* This is the signal we are waiting for. */
td->thrfunc = tk->thrfunc;
td->sival = tk->sival;
pthread_t th;
__pthread_create (&th, &tk->attr, timer_sigev_thread, td);
}
}
__pthread_mutex_unlock (&__timer_active_sigev_thread_lock);
}
}
}
/* Control variable for helper thread creation. */
pthread_once_t __timer_helper_once = PTHREAD_ONCE_INIT;
/* TID of the helper thread. */
pid_t __timer_helper_tid;
/* Reset variables so that after a fork a new helper thread gets started. */
void
__timer_fork_subprocess (void)
{
__timer_helper_once = PTHREAD_ONCE_INIT;
__timer_helper_tid = 0;
}
void
__timer_start_helper_thread (void)
{
/* The helper thread needs only very little resources
and should go away automatically when canceled. */
pthread_attr_t attr;
__pthread_attr_init (&attr);
__pthread_attr_setstacksize (&attr, __pthread_get_minstack (&attr));
/* Block all signals in the helper thread but SIGSETXID. */
sigset_t ss;
__sigfillset (&ss);
__sigdelset (&ss, SIGSETXID);
int res = __pthread_attr_setsigmask_internal (&attr, &ss);
if (res != 0)
{
__pthread_attr_destroy (&attr);
return;
}
/* Create the helper thread for this timer. */
pthread_t th;
res = __pthread_create (&th, &attr, timer_helper_thread, NULL);
if (res == 0)
/* We managed to start the helper thread. */
__timer_helper_tid = ((struct pthread *) th)->tid;
/* No need for the attribute anymore. */
__pthread_attr_destroy (&attr);
}
/* Empty. */