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120 lines
3.3 KiB
C
120 lines
3.3 KiB
C
/* Delaying the delivery of signals to the current process.
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Copyright (C) 2026 Free Software Foundation, Inc.
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This file is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation; either version 2.1 of the
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License, or (at your option) any later version.
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This file is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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/* Written by Bruno Haible. */
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#include <config.h>
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/* Specification. */
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#include "sigdelay.h"
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#include <errno.h>
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#include <stdcountof.h>
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#include <stdlib.h>
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#include "glthread/lock.h"
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#include "thread-optim.h"
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#include "sig-handler.h"
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/* State regarding a single signal. */
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struct state
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{
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/* Number of times sigdelay (SIG_BLOCK, ...) was invoked for this signal. */
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unsigned int count;
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/* If count > 0: The original action for the signal. */
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struct sigaction saved_action;
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/* Whether this signal was caught and is waiting to be re-delivered. */
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unsigned int volatile caught;
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};
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/* The state for all signals.
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NSIG is the maximum signal number + 1. */
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static struct state states[NSIG];
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static _GL_ASYNC_SAFE void
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delaying_handler (int sig)
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{
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if (sig >= 0 && sig < countof (states))
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states[sig].caught = 1;
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}
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/* Lock that makes sigdelay multi-thread safe. */
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gl_lock_define_initialized (static, sigdelay_lock)
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int
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sigdelay (int how, const sigset_t *restrict set, sigset_t *restrict old_set)
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{
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if (!(how == SIG_BLOCK || how == SIG_UNBLOCK))
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{
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errno = EINVAL;
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return -1;
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}
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if (old_set != NULL)
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sigemptyset (old_set);
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bool mt = gl_multithreaded ();
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if (mt) gl_lock_lock (sigdelay_lock);
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if (old_set != NULL)
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for (int sig = 1; sig < countof (states); sig++)
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if (states[sig].count > 0)
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sigaddset (old_set, sig);
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for (int sig = 1; sig < countof (states); sig++)
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if (sigismember (set, sig) > 0)
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{
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switch (how)
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{
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case SIG_BLOCK:
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if (states[sig].count == 0)
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{
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states[sig].caught = 0;
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struct sigaction delaying_action;
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delaying_action.sa_handler = delaying_handler;
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delaying_action.sa_flags = SA_NODEFER;
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sigemptyset (&delaying_action.sa_mask);
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if (sigaction (sig, &delaying_action,
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&states[sig].saved_action) < 0)
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abort ();
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}
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states[sig].count++;
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break;
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case SIG_UNBLOCK:
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if (states[sig].count == 0)
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/* Invalid call. */
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abort ();
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states[sig].count--;
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if (states[sig].count == 0)
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{
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unsigned int caught = states[sig].caught;
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if (sigaction (sig, &states[sig].saved_action, NULL) < 0)
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abort ();
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if (caught)
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raise (sig);
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}
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break;
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}
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}
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if (mt) gl_lock_unlock (sigdelay_lock);
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return 0;
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}
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