diff options
| -rw-r--r-- | fs/eventpoll.c | 38 | ||||
| -rw-r--r-- | include/linux/eventpoll.h | 1 | ||||
| -rw-r--r-- | tools/testing/selftests/Makefile | 2 | ||||
| -rw-r--r-- | tools/testing/selftests/epoll/Makefile | 11 | ||||
| -rw-r--r-- | tools/testing/selftests/epoll/test_epoll.c | 344 |
5 files changed, 392 insertions, 4 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c index cd96649bfe62..da72250ddc1c 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -346,7 +346,7 @@ static inline struct epitem *ep_item_from_epqueue(poll_table *p) /* Tells if the epoll_ctl(2) operation needs an event copy from userspace */ static inline int ep_op_has_event(int op) { - return op != EPOLL_CTL_DEL; + return op == EPOLL_CTL_ADD || op == EPOLL_CTL_MOD; } /* Initialize the poll safe wake up structure */ @@ -676,6 +676,34 @@ static int ep_remove(struct eventpoll *ep, struct epitem *epi) return 0; } +/* + * Disables a "struct epitem" in the eventpoll set. Returns -EBUSY if the item + * had no event flags set, indicating that another thread may be currently + * handling that item's events (in the case that EPOLLONESHOT was being + * used). Otherwise a zero result indicates that the item has been disabled + * from receiving events. A disabled item may be re-enabled via + * EPOLL_CTL_MOD. Must be called with "mtx" held. + */ +static int ep_disable(struct eventpoll *ep, struct epitem *epi) +{ + int result = 0; + unsigned long flags; + + spin_lock_irqsave(&ep->lock, flags); + if (epi->event.events & ~EP_PRIVATE_BITS) { + if (ep_is_linked(&epi->rdllink)) + list_del_init(&epi->rdllink); + /* Ensure ep_poll_callback will not add epi back onto ready + list: */ + epi->event.events &= EP_PRIVATE_BITS; + } + else + result = -EBUSY; + spin_unlock_irqrestore(&ep->lock, flags); + + return result; +} + static void ep_free(struct eventpoll *ep) { struct rb_node *rbp; @@ -1020,8 +1048,6 @@ static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi) rb_insert_color(&epi->rbn, &ep->rbr); } - - #define PATH_ARR_SIZE 5 /* * These are the number paths of length 1 to 5, that we are allowing to emanate @@ -1787,6 +1813,12 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd, } else error = -ENOENT; break; + case EPOLL_CTL_DISABLE: + if (epi) + error = ep_disable(ep, epi); + else + error = -ENOENT; + break; } mutex_unlock(&ep->mtx); diff --git a/include/linux/eventpoll.h b/include/linux/eventpoll.h index f4bb378ccf6a..41085d0f3955 100644 --- a/include/linux/eventpoll.h +++ b/include/linux/eventpoll.h @@ -25,6 +25,7 @@ #define EPOLL_CTL_ADD 1 #define EPOLL_CTL_DEL 2 #define EPOLL_CTL_MOD 3 +#define EPOLL_CTL_DISABLE 4 /* * Request the handling of system wakeup events so as to prevent system suspends diff --git a/tools/testing/selftests/Makefile b/tools/testing/selftests/Makefile index 85baf11e2acd..43480149119e 100644 --- a/tools/testing/selftests/Makefile +++ b/tools/testing/selftests/Makefile @@ -1,4 +1,4 @@ -TARGETS = breakpoints kcmp mqueue vm cpu-hotplug memory-hotplug +TARGETS = breakpoints kcmp mqueue vm cpu-hotplug memory-hotplug epoll all: for TARGET in $(TARGETS); do \ diff --git a/tools/testing/selftests/epoll/Makefile b/tools/testing/selftests/epoll/Makefile new file mode 100644 index 000000000000..19806ed62f50 --- /dev/null +++ b/tools/testing/selftests/epoll/Makefile @@ -0,0 +1,11 @@ +# Makefile for epoll selftests + +all: test_epoll +%: %.c + gcc -pthread -g -o $@ $^ + +run_tests: all + ./test_epoll + +clean: + $(RM) test_epoll diff --git a/tools/testing/selftests/epoll/test_epoll.c b/tools/testing/selftests/epoll/test_epoll.c new file mode 100644 index 000000000000..e0fcff1e8331 --- /dev/null +++ b/tools/testing/selftests/epoll/test_epoll.c @@ -0,0 +1,344 @@ +/* + * tools/testing/selftests/epoll/test_epoll.c + * + * Copyright 2012 Adobe Systems Incorporated + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * Paton J. Lewis <palewis@adobe.com> + * + */ + +#include <errno.h> +#include <fcntl.h> +#include <pthread.h> +#include <stdio.h> +#include <stdlib.h> +#include <unistd.h> +#include <sys/epoll.h> +#include <sys/socket.h> + +/* + * A pointer to an epoll_item_private structure will be stored in the epoll + * item's event structure so that we can get access to the epoll_item_private + * data after calling epoll_wait: + */ +struct epoll_item_private { + int index; /* Position of this struct within the epoll_items array. */ + int fd; + uint32_t events; + pthread_mutex_t mutex; /* Guards the following variables... */ + int stop; + int status; /* Stores any error encountered while handling item. */ + /* The following variable allows us to test whether we have encountered + a problem while attempting to cancel and delete the associated + event. When the test program exits, 'deleted' should be exactly + one. If it is greater than one, then the failed test reflects a real + world situation where we would have tried to access the epoll item's + private data after deleting it: */ + int deleted; +}; + +struct epoll_item_private *epoll_items; + +/* + * Delete the specified item from the epoll set. In a real-world secneario this + * is where we would free the associated data structure, but in this testing + * environment we retain the structure so that we can test for double-deletion: + */ +void delete_item(int index) +{ + __sync_fetch_and_add(&epoll_items[index].deleted, 1); +} + +/* + * A pointer to a read_thread_data structure will be passed as the argument to + * each read thread: + */ +struct read_thread_data { + int stop; + int status; /* Indicates any error encountered by the read thread. */ + int epoll_set; +}; + +/* + * The function executed by the read threads: + */ +void *read_thread_function(void *function_data) +{ + struct read_thread_data *thread_data = + (struct read_thread_data *)function_data; + struct epoll_event event_data; + struct epoll_item_private *item_data; + char socket_data; + + /* Handle events until we encounter an error or this thread's 'stop' + condition is set: */ + while (1) { + int result = epoll_wait(thread_data->epoll_set, + &event_data, + 1, /* Number of desired events */ + 1000); /* Timeout in ms */ + if (result < 0) { + /* Breakpoints signal all threads. Ignore that while + debugging: */ + if (errno == EINTR) + continue; + thread_data->status = errno; + return 0; + } else if (thread_data->stop) + return 0; + else if (result == 0) /* Timeout */ + continue; + + /* We need the mutex here because checking for the stop + condition and re-enabling the epoll item need to be done + together as one atomic operation when EPOLL_CTL_DISABLE is + available: */ + item_data = (struct epoll_item_private *)event_data.data.ptr; + pthread_mutex_lock(&item_data->mutex); + + /* Remove the item from the epoll set if we want to stop + handling that event: */ + if (item_data->stop) + delete_item(item_data->index); + else { + /* Clear the data that was written to the other end of + our non-blocking socket: */ + do { + if (read(item_data->fd, &socket_data, 1) < 1) { + if ((errno == EAGAIN) || + (errno == EWOULDBLOCK)) + break; + else + goto error_unlock; + } + } while (item_data->events & EPOLLET); + + /* The item was one-shot, so re-enable it: */ + event_data.events = item_data->events; + if (epoll_ctl(thread_data->epoll_set, + EPOLL_CTL_MOD, + item_data->fd, + &event_data) < 0) + goto error_unlock; + } + + pthread_mutex_unlock(&item_data->mutex); + } + +error_unlock: + thread_data->status = item_data->status = errno; + pthread_mutex_unlock(&item_data->mutex); + return 0; +} + +/* + * A pointer to a write_thread_data structure will be passed as the argument to + * the write thread: + */ +struct write_thread_data { + int stop; + int status; /* Indicates any error encountered by the write thread. */ + int n_fds; + int *fds; +}; + +/* + * The function executed by the write thread. It writes a single byte to each + * socket in turn until the stop condition for this thread is set. If writing to + * a socket would block (i.e. errno was EAGAIN), we leave that socket alone for + * the moment and just move on to the next socket in the list. We don't care + * about the order in which we deliver events to the epoll set. In fact we don't + * care about the data we're writing to the pipes at all; we just want to + * trigger epoll events: + */ +void *write_thread_function(void *function_data) +{ + const char data = 'X'; + int index; + struct write_thread_data *thread_data = + (struct write_thread_data *)function_data; + while (!write_thread_data->stop) + for (index = 0; + !thread_data->stop && (index < thread_data->n_fds); + ++index) + if ((write(thread_data->fds[index], &data, 1) < 1) && + (errno != EAGAIN) && + (errno != EWOULDBLOCK)) { + write_thread_data->status = errno; + return; + } +} + +/* + * Arguments are currently ignored: + */ +int main(int argc, char **argv) +{ + const int n_read_threads = 100; + const int n_epoll_items = 500; + int index; + int epoll_set = epoll_create1(0); + struct write_thread_data write_thread_data = { + 0, 0, n_epoll_items, malloc(n_epoll_items * sizeof(int)) + }; + struct read_thread_data *read_thread_data = + malloc(n_read_threads * sizeof(struct read_thread_data)); + pthread_t *read_threads = malloc(n_read_threads * sizeof(pthread_t)); + pthread_t write_thread; + + printf("-----------------\n"); + printf("Runing test_epoll\n"); + printf("-----------------\n"); + + epoll_items = malloc(n_epoll_items * sizeof(struct epoll_item_private)); + + if (epoll_set < 0 || epoll_items == 0 || write_thread_data.fds == 0 || + read_thread_data == 0 || read_threads == 0) + goto error; + + if (sysconf(_SC_NPROCESSORS_ONLN) < 2) { + printf("Error: please run this test on a multi-core system.\n"); + goto error; + } + + /* Create the socket pairs and epoll items: */ + for (index = 0; index < n_epoll_items; ++index) { + int socket_pair[2]; + struct epoll_event event_data; + if (socketpair(AF_UNIX, + SOCK_STREAM | SOCK_NONBLOCK, + 0, + socket_pair) < 0) + goto error; + write_thread_data.fds[index] = socket_pair[0]; + epoll_items[index].index = index; + epoll_items[index].fd = socket_pair[1]; + if (pthread_mutex_init(&epoll_items[index].mutex, NULL) != 0) + goto error; + /* We always use EPOLLONESHOT because this test is currently + structured to demonstrate the need for EPOLL_CTL_DISABLE, + which only produces useful information in the EPOLLONESHOT + case (without EPOLLONESHOT, calling epoll_ctl with + EPOLL_CTL_DISABLE will never return EBUSY). If support for + testing events without EPOLLONESHOT is desired, it should + probably be implemented in a separate unit test. */ + epoll_items[index].events = EPOLLIN | EPOLLONESHOT; + if (index < n_epoll_items / 2) + epoll_items[index].events |= EPOLLET; + epoll_items[index].stop = 0; + epoll_items[index].status = 0; + epoll_items[index].deleted = 0; + event_data.events = epoll_items[index].events; + event_data.data.ptr = &epoll_items[index]; + if (epoll_ctl(epoll_set, + EPOLL_CTL_ADD, + epoll_items[index].fd, + &event_data) < 0) + goto error; + } + + /* Create and start the read threads: */ + for (index = 0; index < n_read_threads; ++index) { + read_thread_data[index].stop = 0; + read_thread_data[index].status = 0; + read_thread_data[index].epoll_set = epoll_set; + if (pthread_create(&read_threads[index], + NULL, + read_thread_function, + &read_thread_data[index]) != 0) + goto error; + } + + if (pthread_create(&write_thread, + NULL, + write_thread_function, + &write_thread_data) != 0) + goto error; + + /* Cancel all event pollers: */ +#ifdef EPOLL_CTL_DISABLE + for (index = 0; index < n_epoll_items; ++index) { + pthread_mutex_lock(&epoll_items[index].mutex); + ++epoll_items[index].stop; + if (epoll_ctl(epoll_set, + EPOLL_CTL_DISABLE, + epoll_items[index].fd, + NULL) == 0) + delete_item(index); + else if (errno != EBUSY) { + pthread_mutex_unlock(&epoll_items[index].mutex); + goto error; + } + /* EBUSY means events were being handled; allow the other thread + to delete the item. */ + pthread_mutex_unlock(&epoll_items[index].mutex); + } +#else + for (index = 0; index < n_epoll_items; ++index) { + pthread_mutex_lock(&epoll_items[index].mutex); + ++epoll_items[index].stop; + pthread_mutex_unlock(&epoll_items[index].mutex); + /* Wait in case a thread running read_thread_function is + currently executing code between epoll_wait and + pthread_mutex_lock with this item. Note that a longer delay + would make double-deletion less likely (at the expense of + performance), but there is no guarantee that any delay would + ever be sufficient. Note also that we delete all event + pollers at once for testing purposes, but in a real-world + environment we are likely to want to be able to cancel event + pollers at arbitrary times. Therefore we can't improve this + situation by just splitting this loop into two loops + (i.e. signal 'stop' for all items, sleep, and then delete all + items). We also can't fix the problem via EPOLL_CTL_DEL + because that command can't prevent the case where some other + thread is executing read_thread_function within the region + mentioned above: */ + usleep(1); + pthread_mutex_lock(&epoll_items[index].mutex); + if (!epoll_items[index].deleted) + delete_item(index); + pthread_mutex_unlock(&epoll_items[index].mutex); + } +#endif + + /* Shut down the read threads: */ + for (index = 0; index < n_read_threads; ++index) + __sync_fetch_and_add(&read_thread_data[index].stop, 1); + for (index = 0; index < n_read_threads; ++index) { + if (pthread_join(read_threads[index], NULL) != 0) + goto error; + if (read_thread_data[index].status) + goto error; + } + + /* Shut down the write thread: */ + __sync_fetch_and_add(&write_thread_data.stop, 1); + if ((pthread_join(write_thread, NULL) != 0) || write_thread_data.status) + goto error; + + /* Check for final error conditions: */ + for (index = 0; index < n_epoll_items; ++index) { + if (epoll_items[index].status != 0) + goto error; + if (pthread_mutex_destroy(&epoll_items[index].mutex) < 0) + goto error; + } + for (index = 0; index < n_epoll_items; ++index) + if (epoll_items[index].deleted != 1) { + printf("Error: item data deleted %1d times.\n", + epoll_items[index].deleted); + goto error; + } + + printf("[PASS]\n"); + return 0; + + error: + printf("[FAIL]\n"); + return errno; +} |