epoll: support for disabling items, and a self-test app (03a7beb5) · Commits · 戴 / test

fs/eventpoll.c

+35 −3

Original line number	Diff line number	Diff line
		@@ -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);

include/linux/eventpoll.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -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

tools/testing/selftests/Makefile

+1 −1

Original line number	Diff line number	Diff line
		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 \

tools/testing/selftests/epoll/Makefile

0 → 100644

+11 −0

Original line number	Diff line number	Diff line
		# Makefile for epoll selftests

		all: test_epoll
		%: %.c
		gcc -pthread -g -o $@ $^

		run_tests: all
		./test_epoll

		clean:
		$(RM) test_epoll

tools/testing/selftests/epoll/test_epoll.c

0 → 100644

+344 −0

Original line number	Diff line number	Diff line
		/*
		* 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;
		}

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