Rewrite the POSIX timer functions.
This is a much simpler implementation that lets the kernel
do as much as possible.
Co-authored-by: Jörgen Strand <jorgen.strand@sonymobile.com>
Co-authored-by: Snild Dolkow <snild.dolkow@sonymobile.com>
Change-Id: Iad19f155de977667aea09410266d54e63e8a26bf
diff --git a/libc/bionic/posix_timers.cpp b/libc/bionic/posix_timers.cpp
new file mode 100644
index 0000000..ffe213c
--- /dev/null
+++ b/libc/bionic/posix_timers.cpp
@@ -0,0 +1,221 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "pthread_internal.h"
+#include "private/bionic_futex.h"
+#include "private/bionic_pthread.h"
+#include "private/kernel_sigset_t.h"
+
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+
+// System calls.
+extern "C" int __rt_sigtimedwait(const sigset_t*, siginfo_t*, const struct timespec*, size_t);
+extern "C" int __timer_create(clockid_t, sigevent*, __kernel_timer_t*);
+extern "C" int __timer_delete(__kernel_timer_t);
+extern "C" int __timer_getoverrun(__kernel_timer_t);
+extern "C" int __timer_gettime(__kernel_timer_t, itimerspec*);
+extern "C" int __timer_settime(__kernel_timer_t, int, const itimerspec*, itimerspec*);
+
+// Most POSIX timers are handled directly by the kernel. We translate SIGEV_THREAD timers
+// into SIGEV_THREAD_ID timers so the kernel handles all the time-related stuff and we just
+// need to worry about running user code on a thread.
+
+// We can't use SIGALRM because too many other C library functions throw that around, and since
+// they don't send to a specific thread, all threads are eligible to handle the signal and we can
+// end up with one of our POSIX timer threads handling it (meaning that the intended recipient
+// doesn't). glibc uses SIGRTMIN for its POSIX timer implementation, so in the absence of any
+// reason to use anything else, we use that too.
+static const int TIMER_SIGNAL = SIGRTMIN;
+
+struct PosixTimer {
+ __kernel_timer_t kernel_timer_id;
+
+ int sigev_notify;
+
+ // These fields are only needed for a SIGEV_THREAD timer.
+ pthread_t callback_thread;
+ void (*callback)(sigval_t);
+ sigval_t callback_argument;
+ volatile int exiting;
+};
+
+static __kernel_timer_t to_kernel_timer_id(timer_t timer) {
+ return reinterpret_cast<PosixTimer*>(timer)->kernel_timer_id;
+}
+
+static void* __timer_thread_start(void* arg) {
+ PosixTimer* timer = reinterpret_cast<PosixTimer*>(arg);
+
+ kernel_sigset_t sigset;
+ sigaddset(sigset.get(), TIMER_SIGNAL);
+
+ while (true) {
+ // Wait for a signal...
+ siginfo_t si;
+ memset(&si, 0, sizeof(si));
+ int rc = __rt_sigtimedwait(sigset.get(), &si, NULL, sizeof(sigset));
+ if (rc == -1) {
+ continue;
+ }
+
+ if (si.si_code == SI_TIMER) {
+ // This signal was sent because a timer fired, so call the callback.
+ timer->callback(timer->callback_argument);
+ } else if (si.si_code == SI_TKILL) {
+ // This signal was sent because someone wants us to exit.
+ timer->exiting = 1;
+ __futex_wake(&timer->exiting, INT32_MAX);
+ return NULL;
+ }
+ }
+}
+
+static void __timer_thread_stop(PosixTimer* timer) {
+ pthread_kill(timer->callback_thread, TIMER_SIGNAL);
+
+ // We can't pthread_join because POSIX says "the threads created in response to a timer
+ // expiration are created detached, or in an unspecified way if the thread attribute's
+ // detachstate is PTHREAD_CREATE_JOINABLE".
+ while (timer->exiting == 0) {
+ __futex_wait(&timer->exiting, 0, NULL);
+ }
+}
+
+// http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_create.html
+int timer_create(clockid_t clock_id, sigevent* evp, timer_t* timer_id) {
+ PosixTimer* new_timer = reinterpret_cast<PosixTimer*>(malloc(sizeof(PosixTimer)));
+ if (new_timer == NULL) {
+ return -1;
+ }
+
+ new_timer->sigev_notify = (evp == NULL) ? SIGEV_SIGNAL : evp->sigev_notify;
+
+ // If not a SIGEV_THREAD timer, the kernel can handle it without our help.
+ if (new_timer->sigev_notify != SIGEV_THREAD) {
+ if (__timer_create(clock_id, evp, &new_timer->kernel_timer_id) == -1) {
+ free(new_timer);
+ return -1;
+ }
+
+ *timer_id = new_timer;
+ return 0;
+ }
+
+ // Otherwise, this must be SIGEV_THREAD timer...
+ new_timer->callback = evp->sigev_notify_function;
+ new_timer->callback_argument = evp->sigev_value;
+ new_timer->exiting = 0;
+
+ // Check arguments that the kernel doesn't care about but we do.
+ if (new_timer->callback == NULL) {
+ free(new_timer);
+ errno = EINVAL;
+ return -1;
+ }
+
+ // Create this timer's thread.
+ pthread_attr_t thread_attributes;
+ if (evp->sigev_notify_attributes == NULL) {
+ pthread_attr_init(&thread_attributes);
+ } else {
+ thread_attributes = *reinterpret_cast<pthread_attr_t*>(evp->sigev_notify_attributes);
+ }
+ pthread_attr_setdetachstate(&thread_attributes, PTHREAD_CREATE_DETACHED);
+
+ // We start the thread with TIMER_SIGNAL blocked by blocking the signal here and letting it
+ // inherit. If it tried to block the signal itself, there would be a race.
+ kernel_sigset_t sigset;
+ sigaddset(sigset.get(), TIMER_SIGNAL);
+ kernel_sigset_t old_sigset;
+ pthread_sigmask(SIG_BLOCK, sigset.get(), old_sigset.get());
+
+ int rc = pthread_create(&new_timer->callback_thread, &thread_attributes, __timer_thread_start, new_timer);
+
+ pthread_sigmask(SIG_SETMASK, old_sigset.get(), NULL);
+
+ if (rc != 0) {
+ free(new_timer);
+ errno = rc;
+ return -1;
+ }
+
+ sigevent se = *evp;
+ se.sigev_signo = TIMER_SIGNAL;
+ se.sigev_notify = SIGEV_THREAD_ID;
+ se.sigev_notify_thread_id = __pthread_gettid(new_timer->callback_thread);
+ if (__timer_create(clock_id, &se, &new_timer->kernel_timer_id) == -1) {
+ __timer_thread_stop(new_timer);
+ free(new_timer);
+ return -1;
+ }
+
+ // Give the thread a meaningful name.
+ // It can't do this itself because the kernel timer isn't created until after it's running.
+ char name[32];
+ snprintf(name, sizeof(name), "POSIX interval timer %d", to_kernel_timer_id(new_timer));
+ pthread_setname_np(new_timer->callback_thread, name);
+
+ *timer_id = new_timer;
+ return 0;
+}
+
+// http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_delete.html
+int timer_delete(timer_t id) {
+ int rc = __timer_delete(to_kernel_timer_id(id));
+ if (rc == -1) {
+ return -1;
+ }
+
+ PosixTimer* timer = reinterpret_cast<PosixTimer*>(id);
+
+ // Make sure the timer's thread has exited before we free the timer data.
+ if (timer->sigev_notify == SIGEV_THREAD) {
+ __timer_thread_stop(timer);
+ }
+
+ free(timer);
+
+ return 0;
+}
+
+// http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_getoverrun.html
+int timer_gettime(timer_t id, itimerspec* ts) {
+ return __timer_gettime(to_kernel_timer_id(id), ts);
+}
+
+// http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_getoverrun.html
+int timer_settime(timer_t id, int flags, const itimerspec* ts, itimerspec* ots) {
+ return __timer_settime(to_kernel_timer_id(id), flags, ts, ots);
+}
+
+// http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_getoverrun.html
+int timer_getoverrun(timer_t id) {
+ return __timer_getoverrun(to_kernel_timer_id(id));
+}