From: compudj Date: Thu, 17 Jul 2008 21:34:18 +0000 (+0000) Subject: fix lttd mutexes X-Git-Tag: 0.80~66 X-Git-Url: http://git.lttng.org/?p=ltt-control.git;a=commitdiff_plain;h=314825295f092965db3df0072f0b2fde4142e8dd fix lttd mutexes git-svn-id: http://ltt.polymtl.ca/svn@2967 04897980-b3bd-0310-b5e0-8ef037075253 --- diff --git a/ltt-control/lttd/lttd.c b/ltt-control/lttd/lttd.c index 4764838..b001426 100644 --- a/ltt-control/lttd/lttd.c +++ b/ltt-control/lttd/lttd.c @@ -5,6 +5,7 @@ * This is a simple daemon that reads a few relay+debugfs channels and save * them in a trace. * + * CPU hot-plugging is supported using inotify. * * Copyright 2005 - * Mathieu Desnoyers @@ -117,6 +118,16 @@ struct inotify_watch_array { int num; }; + + +struct channel_trace_fd fd_pairs = { NULL, 0 }; +int inotify_fd = -1; +struct inotify_watch_array inotify_watch_array = { NULL, 0 }; + +/* protects fd_pairs and inotify_watch_array */ +pthread_rwlock_t fd_pairs_lock = PTHREAD_RWLOCK_INITIALIZER; + + static char *trace_name = NULL; static char *channel_name = NULL; static int daemon_mode = 0; @@ -577,6 +588,10 @@ int read_inotify(int inotify_fd, offset = 0; len = read(inotify_fd, buf, sizeof(struct inotify_event) + PATH_MAX); if(len < 0) { + + if(errno == EAGAIN) + return 0; /* another thread got the data before us */ + printf("Error in read from inotify FD %s.\n", strerror(len)); return -1; } @@ -628,10 +643,11 @@ int read_inotify(int inotify_fd, * full. */ -int read_channels(unsigned int thread_num, struct channel_trace_fd *fd_pairs, +int read_channels(unsigned long thread_num, struct channel_trace_fd *fd_pairs, int inotify_fd, struct inotify_watch_array *iwatch_array) { struct pollfd *pollfd = NULL; + int num_pollfd; int i,j; int num_rdy, num_hup; int high_prio; @@ -645,6 +661,8 @@ int read_channels(unsigned int thread_num, struct channel_trace_fd *fd_pairs, inotify_fds = 0; #endif + pthread_rwlock_rdlock(&fd_pairs_lock); + /* Start polling the FD. Keep one fd for inotify */ pollfd = malloc((inotify_fds + fd_pairs->num_pairs) * sizeof(struct pollfd)); @@ -657,7 +675,11 @@ int read_channels(unsigned int thread_num, struct channel_trace_fd *fd_pairs, pollfd[inotify_fds+i].fd = fd_pairs->pair[i].channel; pollfd[inotify_fds+i].events = POLLIN|POLLPRI; } - + num_pollfd = inotify_fds + fd_pairs->num_pairs; + + + pthread_rwlock_unlock(&fd_pairs_lock); + while(1) { high_prio = 0; num_hup = 0; @@ -665,13 +687,14 @@ int read_channels(unsigned int thread_num, struct channel_trace_fd *fd_pairs, printf("Press a key for next poll...\n"); char buf[1]; read(STDIN_FILENO, &buf, 1); - printf("Next poll (polling %d fd) :\n", 1+fd_pairs->num_pairs); + printf("Next poll (polling %d fd) :\n", num_pollfd); #endif //DEBUG /* Have we received a signal ? */ if(quit_program) break; - num_rdy = poll(pollfd, inotify_fds+fd_pairs->num_pairs, -1); + num_rdy = poll(pollfd, num_pollfd, -1); + if(num_rdy == -1) { perror("Poll error"); goto free_fd; @@ -691,20 +714,18 @@ int read_channels(unsigned int thread_num, struct channel_trace_fd *fd_pairs, break; case POLLPRI: case POLLIN: + printf("Polling inotify fd %d : data ready.\n", pollfd[0].fd); - old_num = fd_pairs->num_pairs; + + pthread_rwlock_wrlock(&fd_pairs_lock); read_inotify(inotify_fd, fd_pairs, iwatch_array); - pollfd = realloc(pollfd, - (inotify_fds + fd_pairs->num_pairs) * sizeof(struct pollfd)); - for(i=old_num;inum_pairs;i++) { - pollfd[inotify_fds+i].fd = fd_pairs->pair[i].channel; - pollfd[inotify_fds+i].events = POLLIN|POLLPRI; - } + pthread_rwlock_unlock(&fd_pairs_lock); + break; } #endif - for(i=inotify_fds;inum_pairs;i++) { + for(i=inotify_fds;ipair[i-inotify_fds].mutex) == 0) { printf("Urgent read on fd %d\n", pollfd[i].fd); /* Take care of high priority channels first. */ @@ -731,16 +753,18 @@ int read_channels(unsigned int thread_num, struct channel_trace_fd *fd_pairs, if(ret) printf("Error in mutex unlock : %s\n", strerror(ret)); } + pthread_rwlock_unlock(&fd_pairs_lock); break; } } /* If every buffer FD has hung up, we end the read loop here */ - if(num_hup == fd_pairs->num_pairs) break; + if(num_hup == num_pollfd - inotify_fds) break; if(!high_prio) { - for(i=inotify_fds;inum_pairs;i++) { + for(i=inotify_fds;ipair[i-inotify_fds].mutex) == 0) { /* Take care of low priority channels. */ printf("Normal read on fd %d\n", pollfd[i].fd); @@ -752,11 +776,34 @@ int read_channels(unsigned int thread_num, struct channel_trace_fd *fd_pairs, if(ret) printf("Error in mutex unlock : %s\n", strerror(ret)); } + pthread_rwlock_unlock(&fd_pairs_lock); break; } } } + /* Update pollfd array if an entry was added to fd_pairs */ + pthread_rwlock_rdlock(&fd_pairs_lock); + if((inotify_fds + fd_pairs->num_pairs) != num_pollfd) { + pollfd = realloc(pollfd, + (inotify_fds + fd_pairs->num_pairs) * sizeof(struct pollfd)); + for(i=num_pollfd-inotify_fds;inum_pairs;i++) { + pollfd[inotify_fds+i].fd = fd_pairs->pair[i].channel; + pollfd[inotify_fds+i].events = POLLIN|POLLPRI; + } + num_pollfd = fd_pairs->num_pairs + inotify_fds; + } + pthread_rwlock_unlock(&fd_pairs_lock); + + /* NB: If the fd_pairs structure is updated by another thread from this + * point forward, the current thread will wait in the poll without + * monitoring the new channel. However, this thread will add the + * new channel on next poll (and this should not take too much time + * on a loaded system). + * + * This event is quite unlikely and can only occur if a CPU is + * hot-plugged while multple lttd threads are running. + */ } free_fd: @@ -786,13 +833,21 @@ void close_channel_trace_pairs(struct channel_trace_fd *fd_pairs, int inotify_fd /* Thread worker */ void * thread_main(void *arg) { - struct channel_trace_fd fd_pairs = { NULL, 0 }; - int inotify_fd = -1; - struct inotify_watch_array inotify_watch_array = { NULL, 0 }; + long ret; + unsigned long thread_num = (unsigned long)arg; + + ret = read_channels(thread_num, &fd_pairs, inotify_fd, &inotify_watch_array); + + return (void*)ret; +} + + +int channels_init() +{ int ret = 0; - unsigned int thread_num = (unsigned int)arg; inotify_fd = inotify_init(); + fcntl(inotify_fd, F_SETFL, O_NONBLOCK); if(ret = open_channel_trace_pairs(channel_name, trace_name, &fd_pairs, &inotify_fd, &inotify_watch_array)) @@ -801,24 +856,22 @@ void * thread_main(void *arg) if(ret = map_channels(&fd_pairs, 0, fd_pairs.num_pairs)) goto close_channel; - ret = read_channels(thread_num, &fd_pairs, inotify_fd, &inotify_watch_array); - - ret |= unmap_channels(&fd_pairs); + return 0; close_channel: close_channel_trace_pairs(&fd_pairs, inotify_fd, &inotify_watch_array); if(inotify_fd >= 0) close(inotify_fd); - - return (void*)ret; + return ret; } + int main(int argc, char ** argv) { int ret = 0; struct sigaction act; pthread_t *tids; - unsigned int i; + unsigned long i; void *tret; ret = parse_arguments(argc, argv); @@ -849,6 +902,9 @@ int main(int argc, char ** argv) sigaction(SIGQUIT, &act, NULL); sigaction(SIGINT, &act, NULL); + if(ret = channels_init()) + return ret; + tids = malloc(sizeof(pthread_t) * num_threads); for(i=0; i= 0) + close(inotify_fd); return ret; }