Priprava na semafor, zatim obsahuje ZAVAZNY DEADLOCK

[mirrors/Programs.git] / c / pthread_extra / pthread_pause.c

diff --git a/c/pthread_extra/pthread_pause.c b/c/pthread_extra/pthread_pause.c
index 103283d755f13966dfac0f4c4298cd5460a5853b..a9ce5dce3c487e87613fff24d90c39fe045f5741 100644 (file)
--- a/c/pthread_extra/pthread_pause.c
+++ b/c/pthread_extra/pthread_pause.c
@@ -3,6 +3,7 @@
 #include <pthread.h>
 #include <pthread_extra.h>
 #include <signal.h>
+#include <semaphore.h>
 #include <errno.h>
 #include <unistd.h>
 #include <sys/resource.h>
@@ -12,8 +13,20 @@
 #include <assert.h>
 //#include <sys/time.h>
 
+//Mutex that ensures proper serialization of (un)pause calls
+//pthread_mutex_t pthread_pause_mutex = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
+
+//Semaphore that ensures proper serialization of (un)pause signals
+sem_t pthread_pause_sem;
+//Once control to init the semaphore (and possibly other stuff)
+pthread_once_t pthread_pause_once_ctrl = PTHREAD_ONCE_INIT;
+void pthread_pause_once(void) {
+       sem_init(&pthread_pause_sem, 0, 1);
+}
+void pthread_pause_init() { pthread_once(&pthread_pause_once_ctrl, &pthread_pause_once); }
+
 ///When this variable is nonzero, only referenced thread is allowed to run
-///Access has to be protected by pthread_user_data_lock()
+///Access has to be protected by pthread_user_data_lock() and pthread_pause_sem;
 pthread_t pthread_pause_holder = PTHREAD_XNULL;
 
 void pthread_pause_handler(const int signal, siginfo_t *info, void *ptr) {
@@ -21,20 +34,14 @@ void pthread_pause_handler(const int signal, siginfo_t *info, void *ptr) {
        int run = info->si_value.sival_int;
        //(void)td;
 
-       //Do nothing when there are more signals pending (to cleanup the queue)
-       sigset_t pending;
-       sigpending(&pending);
-       if(sigismember(&pending, PTHREAD_XSIG_STOP)) return;
+       //Post semaphore to confirm that signal is handled
+       sem_post(&pthread_pause_sem);
 
        //Keep waiting for signals until we are supposed to be running
-       sigset_t sigset;
-       sigfillset(&sigset);
-       sigdelset(&sigset, PTHREAD_XSIG_STOP);
-
-       //printf("RCV: %p = %p\n", (void *)pthread_user_data_internal(pthread_self()), (void *)td);
-
-       //if(!pthread_user_data_internal(pthread_self())->running) {
        if(!run) {
+               sigset_t sigset;
+               sigfillset(&sigset);
+               sigdelset(&sigset, PTHREAD_XSIG_STOP);
                sigsuspend(&sigset);
        }
 }
@@ -46,8 +53,10 @@ void pthread_pause_enable() {
        //Nesting signals too deep is not good for stack
        //You can get runtime stats using following command:
        //grep -i sig /proc/$(pgrep binary)/status
-       struct rlimit sigq = {.rlim_cur = 32, .rlim_max=32};
-       setrlimit(RLIMIT_SIGPENDING, &sigq);
+       //struct rlimit sigq = {.rlim_cur = 32, .rlim_max=32};
+       //setrlimit(RLIMIT_SIGPENDING, &sigq);
+
+       pthread_pause_init(); //Make sure semaphore is init'd
 
        //Prepare signal mask
        sigset_t sigset;
@@ -72,11 +81,17 @@ void pthread_pause_disable() {
        //Add thread to internal registry
        //pthread_user_data_internal(pthread_self());
 
+       pthread_pause_init(); //Make sure semaphore is init'd
+
        //Block signal
        sigset_t sigset;
        sigemptyset(&sigset);
        sigaddset(&sigset, PTHREAD_XSIG_STOP);
+
+       //Make sure all signals are dispatched before we block them
+       sem_wait(&pthread_pause_sem);
        pthread_sigmask(SIG_BLOCK, &sigset, NULL);
+       sem_post(&pthread_pause_sem);
 }
 
 /*
@@ -92,7 +107,14 @@ int pthread_pause_reschedule(pthread_t thread) {
 */
 
 int pthread_pause_reschedule(pthread_t thread) {
-       //Decide if the thread should run
+       //Decide if the thread should run and signal it
+
+       //Wait for semaphore which means signal queue is empty
+       pthread_pause_init(); //Make sure semaphore is init'd
+       sem_wait(&pthread_pause_sem);
+
+       //Only call this if you already acquired pthread_pause_sem semaphore!!!!
+       //Otherwise call pthread_pause_reschedule()
 
        pthread_user_data_lock();
        //Check if thread has running flag
@@ -108,6 +130,11 @@ int pthread_pause_reschedule(pthread_t thread) {
        while(pthread_sigqueue(thread, PTHREAD_XSIG_STOP,
                (const union sigval){.sival_int=run}
                ) == EAGAIN) usleep(1000);
+
+       //Wait for signal to be delivered
+       sem_wait(&pthread_pause_sem);
+       sem_post(&pthread_pause_sem);
+
        return 0;
 }
 
@@ -121,8 +148,8 @@ int pthread_pause(pthread_t thread) {
        //Set thread as paused and notify it via signal (wait when queue full)
        pthread_user_data_lock();
        pthread_user_data_internal(thread)->running = 0;
-       pthread_user_data_unlock();
        pthread_pause_reschedule(thread);
+       pthread_user_data_unlock();
        return 0;
 }
 
@@ -130,8 +157,8 @@ int pthread_unpause(pthread_t thread) {
        //Set thread as running and notify it via signal (wait when queue full)
        pthread_user_data_lock();
        pthread_user_data_internal(thread)->running = 1;
-       pthread_user_data_unlock();
        pthread_pause_reschedule(thread);
+       pthread_user_data_unlock();
        return 0;
 }
 
@@ -139,8 +166,8 @@ int pthread_pause_all() {
        pthread_user_data_lock();
        if(pthread_pause_holder!=PTHREAD_XNULL) assert(pthread_equal(pthread_pause_holder, pthread_self()));
        pthread_pause_holder = pthread_self();
-       pthread_user_data_unlock();
        pthread_user_data_internal_iterate(&pthread_pause_reschedule, NULL);
+       pthread_user_data_unlock();
        return 0;
 }
 
@@ -148,8 +175,8 @@ int pthread_unpause_all() {
        pthread_user_data_lock();
        if(pthread_pause_holder!=PTHREAD_XNULL) assert(pthread_equal(pthread_pause_holder, pthread_self()));
        pthread_pause_holder = PTHREAD_XNULL;
-       pthread_user_data_unlock();
        pthread_user_data_internal_iterate(&pthread_pause_reschedule, NULL);
+       pthread_user_data_unlock();
        return 0;
 }