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/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* epoll(7) file descriptor monitoring
*/
#include "qemu/osdep.h"
#include <sys/epoll.h>
#include "qemu/rcu_queue.h"
#include "aio-posix.h"
/* The fd number threshold to switch to epoll */
#define EPOLL_ENABLE_THRESHOLD 64
void fdmon_epoll_disable(AioContext *ctx)
{
if (ctx->epollfd >= 0) {
close(ctx->epollfd);
ctx->epollfd = -1;
}
/* Switch back */
ctx->fdmon_ops = &fdmon_poll_ops;
}
static inline int epoll_events_from_pfd(int pfd_events)
{
return (pfd_events & G_IO_IN ? EPOLLIN : 0) |
(pfd_events & G_IO_OUT ? EPOLLOUT : 0) |
(pfd_events & G_IO_HUP ? EPOLLHUP : 0) |
(pfd_events & G_IO_ERR ? EPOLLERR : 0);
}
static void fdmon_epoll_update(AioContext *ctx,
AioHandler *old_node,
AioHandler *new_node)
{
struct epoll_event event = {
.data.ptr = new_node,
.events = new_node ? epoll_events_from_pfd(new_node->pfd.events) : 0,
};
int r;
if (!new_node) {
r = epoll_ctl(ctx->epollfd, EPOLL_CTL_DEL, old_node->pfd.fd, &event);
} else if (!old_node) {
r = epoll_ctl(ctx->epollfd, EPOLL_CTL_ADD, new_node->pfd.fd, &event);
} else {
r = epoll_ctl(ctx->epollfd, EPOLL_CTL_MOD, new_node->pfd.fd, &event);
}
if (r) {
fdmon_epoll_disable(ctx);
}
}
static int fdmon_epoll_wait(AioContext *ctx, AioHandlerList *ready_list,
int64_t timeout)
{
GPollFD pfd = {
.fd = ctx->epollfd,
.events = G_IO_IN | G_IO_OUT | G_IO_HUP | G_IO_ERR,
};
AioHandler *node;
int i, ret = 0;
struct epoll_event events[128];
/* Fall back while external clients are disabled */
if (qatomic_read(&ctx->external_disable_cnt)) {
return fdmon_poll_ops.wait(ctx, ready_list, timeout);
}
if (timeout > 0) {
ret = qemu_poll_ns(&pfd, 1, timeout);
if (ret > 0) {
timeout = 0;
}
}
if (timeout <= 0 || ret > 0) {
ret = epoll_wait(ctx->epollfd, events,
ARRAY_SIZE(events),
timeout);
if (ret <= 0) {
goto out;
}
for (i = 0; i < ret; i++) {
int ev = events[i].events;
int revents = (ev & EPOLLIN ? G_IO_IN : 0) |
(ev & EPOLLOUT ? G_IO_OUT : 0) |
(ev & EPOLLHUP ? G_IO_HUP : 0) |
(ev & EPOLLERR ? G_IO_ERR : 0);
node = events[i].data.ptr;
aio_add_ready_handler(ready_list, node, revents);
}
}
out:
return ret;
}
static const FDMonOps fdmon_epoll_ops = {
.update = fdmon_epoll_update,
.wait = fdmon_epoll_wait,
.need_wait = aio_poll_disabled,
};
static bool fdmon_epoll_try_enable(AioContext *ctx)
{
AioHandler *node;
struct epoll_event event;
QLIST_FOREACH_RCU(node, &ctx->aio_handlers, node) {
int r;
if (QLIST_IS_INSERTED(node, node_deleted) || !node->pfd.events) {
continue;
}
event.events = epoll_events_from_pfd(node->pfd.events);
event.data.ptr = node;
r = epoll_ctl(ctx->epollfd, EPOLL_CTL_ADD, node->pfd.fd, &event);
if (r) {
return false;
}
}
ctx->fdmon_ops = &fdmon_epoll_ops;
return true;
}
bool fdmon_epoll_try_upgrade(AioContext *ctx, unsigned npfd)
{
bool ok;
if (ctx->epollfd < 0) {
return false;
}
/* Do not upgrade while external clients are disabled */
if (qatomic_read(&ctx->external_disable_cnt)) {
return false;
}
if (npfd < EPOLL_ENABLE_THRESHOLD) {
return false;
}
/* The list must not change while we add fds to epoll */
if (!qemu_lockcnt_dec_if_lock(&ctx->list_lock)) {
return false;
}
ok = fdmon_epoll_try_enable(ctx);
qemu_lockcnt_inc_and_unlock(&ctx->list_lock);
if (!ok) {
fdmon_epoll_disable(ctx);
}
return ok;
}
void fdmon_epoll_setup(AioContext *ctx)
{
ctx->epollfd = epoll_create1(EPOLL_CLOEXEC);
if (ctx->epollfd == -1) {
fprintf(stderr, "Failed to create epoll instance: %s", strerror(errno));
}
}
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