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Diffstat (limited to 'fs/eventpoll.c')
-rw-r--r--fs/eventpoll.c262
1 files changed, 209 insertions, 53 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 74598f67efeb..9ad17b15b454 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -34,10 +34,14 @@
#include <linux/mutex.h>
#include <linux/anon_inodes.h>
#include <linux/device.h>
+#include <linux/freezer.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/mman.h>
#include <linux/atomic.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/compat.h>
/*
* LOCKING:
@@ -102,7 +106,7 @@
struct epoll_filefd {
struct file *file;
int fd;
-};
+} __packed;
/*
* Structure used to track possible nested calls, for too deep recursions
@@ -126,6 +130,8 @@ struct nested_calls {
/*
* Each file descriptor added to the eventpoll interface will
* have an entry of this type linked to the "rbr" RB tree.
+ * Avoid increasing the size of this struct, there can be many thousands
+ * of these on a server and we do not want this to take another cache line.
*/
struct epitem {
/* RB tree node used to link this structure to the eventpoll RB tree */
@@ -156,7 +162,7 @@ struct epitem {
struct list_head fllink;
/* wakeup_source used when EPOLLWAKEUP is set */
- struct wakeup_source *ws;
+ struct wakeup_source __rcu *ws;
/* The structure that describe the interested events and the source fd */
struct epoll_event event;
@@ -534,6 +540,38 @@ static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi)
}
}
+/* call only when ep->mtx is held */
+static inline struct wakeup_source *ep_wakeup_source(struct epitem *epi)
+{
+ return rcu_dereference_check(epi->ws, lockdep_is_held(&epi->ep->mtx));
+}
+
+/* call only when ep->mtx is held */
+static inline void ep_pm_stay_awake(struct epitem *epi)
+{
+ struct wakeup_source *ws = ep_wakeup_source(epi);
+
+ if (ws)
+ __pm_stay_awake(ws);
+}
+
+static inline bool ep_has_wakeup_source(struct epitem *epi)
+{
+ return rcu_access_pointer(epi->ws) ? true : false;
+}
+
+/* call when ep->mtx cannot be held (ep_poll_callback) */
+static inline void ep_pm_stay_awake_rcu(struct epitem *epi)
+{
+ struct wakeup_source *ws;
+
+ rcu_read_lock();
+ ws = rcu_dereference(epi->ws);
+ if (ws)
+ __pm_stay_awake(ws);
+ rcu_read_unlock();
+}
+
/**
* ep_scan_ready_list - Scans the ready list in a way that makes possible for
* the scan code, to call f_op->poll(). Also allows for
@@ -597,7 +635,7 @@ static int ep_scan_ready_list(struct eventpoll *ep,
*/
if (!ep_is_linked(&epi->rdllink)) {
list_add_tail(&epi->rdllink, &ep->rdllist);
- __pm_stay_awake(epi->ws);
+ ep_pm_stay_awake(epi);
}
}
/*
@@ -666,7 +704,7 @@ static int ep_remove(struct eventpoll *ep, struct epitem *epi)
list_del_init(&epi->rdllink);
spin_unlock_irqrestore(&ep->lock, flags);
- wakeup_source_unregister(epi->ws);
+ wakeup_source_unregister(ep_wakeup_source(epi));
/* At this point it is safe to free the eventpoll item */
kmem_cache_free(epi_cache, epi);
@@ -709,11 +747,15 @@ static void ep_free(struct eventpoll *ep)
* point we are sure no poll callbacks will be lingering around, and also by
* holding "epmutex" we can be sure that no file cleanup code will hit
* us during this operation. So we can avoid the lock on "ep->lock".
+ * We do not need to lock ep->mtx, either, we only do it to prevent
+ * a lockdep warning.
*/
+ mutex_lock(&ep->mtx);
while ((rbp = rb_first(&ep->rbr)) != NULL) {
epi = rb_entry(rbp, struct epitem, rbn);
ep_remove(ep, epi);
}
+ mutex_unlock(&ep->mtx);
mutex_unlock(&epmutex);
mutex_destroy(&ep->mtx);
@@ -732,6 +774,13 @@ static int ep_eventpoll_release(struct inode *inode, struct file *file)
return 0;
}
+static inline unsigned int ep_item_poll(struct epitem *epi, poll_table *pt)
+{
+ pt->_key = epi->event.events;
+
+ return epi->ffd.file->f_op->poll(epi->ffd.file, pt) & epi->event.events;
+}
+
static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head,
void *priv)
{
@@ -739,10 +788,9 @@ static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head,
poll_table pt;
init_poll_funcptr(&pt, NULL);
+
list_for_each_entry_safe(epi, tmp, head, rdllink) {
- pt._key = epi->event.events;
- if (epi->ffd.file->f_op->poll(epi->ffd.file, &pt) &
- epi->event.events)
+ if (ep_item_poll(epi, &pt))
return POLLIN | POLLRDNORM;
else {
/*
@@ -750,7 +798,7 @@ static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head,
* callback, but it's not actually ready, as far as
* caller requested events goes. We can remove it here.
*/
- __pm_relax(epi->ws);
+ __pm_relax(ep_wakeup_source(epi));
list_del_init(&epi->rdllink);
}
}
@@ -783,8 +831,34 @@ static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait)
return pollflags != -1 ? pollflags : 0;
}
+#ifdef CONFIG_PROC_FS
+static int ep_show_fdinfo(struct seq_file *m, struct file *f)
+{
+ struct eventpoll *ep = f->private_data;
+ struct rb_node *rbp;
+ int ret = 0;
+
+ mutex_lock(&ep->mtx);
+ for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {
+ struct epitem *epi = rb_entry(rbp, struct epitem, rbn);
+
+ ret = seq_printf(m, "tfd: %8d events: %8x data: %16llx\n",
+ epi->ffd.fd, epi->event.events,
+ (long long)epi->event.data);
+ if (ret)
+ break;
+ }
+ mutex_unlock(&ep->mtx);
+
+ return ret;
+}
+#endif
+
/* File callbacks that implement the eventpoll file behaviour */
static const struct file_operations eventpoll_fops = {
+#ifdef CONFIG_PROC_FS
+ .show_fdinfo = ep_show_fdinfo,
+#endif
.release = ep_eventpoll_release,
.poll = ep_eventpoll_poll,
.llseek = noop_llseek,
@@ -956,7 +1030,7 @@ static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *k
/* If this file is already in the ready list we exit soon */
if (!ep_is_linked(&epi->rdllink)) {
list_add_tail(&epi->rdllink, &ep->rdllist);
- __pm_stay_awake(epi->ws);
+ ep_pm_stay_awake_rcu(epi);
}
/*
@@ -1118,6 +1192,7 @@ static int reverse_path_check(void)
static int ep_create_wakeup_source(struct epitem *epi)
{
const char *name;
+ struct wakeup_source *ws;
if (!epi->ep->ws) {
epi->ep->ws = wakeup_source_register("eventpoll");
@@ -1126,17 +1201,29 @@ static int ep_create_wakeup_source(struct epitem *epi)
}
name = epi->ffd.file->f_path.dentry->d_name.name;
- epi->ws = wakeup_source_register(name);
- if (!epi->ws)
+ ws = wakeup_source_register(name);
+
+ if (!ws)
return -ENOMEM;
+ rcu_assign_pointer(epi->ws, ws);
return 0;
}
-static void ep_destroy_wakeup_source(struct epitem *epi)
+/* rare code path, only used when EPOLL_CTL_MOD removes a wakeup source */
+static noinline void ep_destroy_wakeup_source(struct epitem *epi)
{
- wakeup_source_unregister(epi->ws);
- epi->ws = NULL;
+ struct wakeup_source *ws = ep_wakeup_source(epi);
+
+ RCU_INIT_POINTER(epi->ws, NULL);
+
+ /*
+ * wait for ep_pm_stay_awake_rcu to finish, synchronize_rcu is
+ * used internally by wakeup_source_remove, too (called by
+ * wakeup_source_unregister), so we cannot use call_rcu
+ */
+ synchronize_rcu();
+ wakeup_source_unregister(ws);
}
/*
@@ -1171,13 +1258,12 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
if (error)
goto error_create_wakeup_source;
} else {
- epi->ws = NULL;
+ RCU_INIT_POINTER(epi->ws, NULL);
}
/* Initialize the poll table using the queue callback */
epq.epi = epi;
init_poll_funcptr(&epq.pt, ep_ptable_queue_proc);
- epq.pt._key = event->events;
/*
* Attach the item to the poll hooks and get current event bits.
@@ -1186,7 +1272,7 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
* this operation completes, the poll callback can start hitting
* the new item.
*/
- revents = tfile->f_op->poll(tfile, &epq.pt);
+ revents = ep_item_poll(epi, &epq.pt);
/*
* We have to check if something went wrong during the poll wait queue
@@ -1219,7 +1305,7 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
/* If the file is already "ready" we drop it inside the ready list */
if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) {
list_add_tail(&epi->rdllink, &ep->rdllist);
- __pm_stay_awake(epi->ws);
+ ep_pm_stay_awake(epi);
/* Notify waiting tasks that events are available */
if (waitqueue_active(&ep->wq))
@@ -1260,7 +1346,7 @@ error_unregister:
list_del_init(&epi->rdllink);
spin_unlock_irqrestore(&ep->lock, flags);
- wakeup_source_unregister(epi->ws);
+ wakeup_source_unregister(ep_wakeup_source(epi));
error_create_wakeup_source:
kmem_cache_free(epi_cache, epi);
@@ -1285,21 +1371,40 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_even
* otherwise we might miss an event that happens between the
* f_op->poll() call and the new event set registering.
*/
- epi->event.events = event->events;
- pt._key = event->events;
+ epi->event.events = event->events; /* need barrier below */
epi->event.data = event->data; /* protected by mtx */
if (epi->event.events & EPOLLWAKEUP) {
- if (!epi->ws)
+ if (!ep_has_wakeup_source(epi))
ep_create_wakeup_source(epi);
- } else if (epi->ws) {
+ } else if (ep_has_wakeup_source(epi)) {
ep_destroy_wakeup_source(epi);
}
/*
+ * The following barrier has two effects:
+ *
+ * 1) Flush epi changes above to other CPUs. This ensures
+ * we do not miss events from ep_poll_callback if an
+ * event occurs immediately after we call f_op->poll().
+ * We need this because we did not take ep->lock while
+ * changing epi above (but ep_poll_callback does take
+ * ep->lock).
+ *
+ * 2) We also need to ensure we do not miss _past_ events
+ * when calling f_op->poll(). This barrier also
+ * pairs with the barrier in wq_has_sleeper (see
+ * comments for wq_has_sleeper).
+ *
+ * This barrier will now guarantee ep_poll_callback or f_op->poll
+ * (or both) will notice the readiness of an item.
+ */
+ smp_mb();
+
+ /*
* Get current event bits. We can safely use the file* here because
* its usage count has been increased by the caller of this function.
*/
- revents = epi->ffd.file->f_op->poll(epi->ffd.file, &pt);
+ revents = ep_item_poll(epi, &pt);
/*
* If the item is "hot" and it is not registered inside the ready
@@ -1309,7 +1414,7 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_even
spin_lock_irq(&ep->lock);
if (!ep_is_linked(&epi->rdllink)) {
list_add_tail(&epi->rdllink, &ep->rdllist);
- __pm_stay_awake(epi->ws);
+ ep_pm_stay_awake(epi);
/* Notify waiting tasks that events are available */
if (waitqueue_active(&ep->wq))
@@ -1335,6 +1440,7 @@ static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head,
unsigned int revents;
struct epitem *epi;
struct epoll_event __user *uevent;
+ struct wakeup_source *ws;
poll_table pt;
init_poll_funcptr(&pt, NULL);
@@ -1357,14 +1463,16 @@ static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head,
* instead, but then epi->ws would temporarily be out of sync
* with ep_is_linked().
*/
- if (epi->ws && epi->ws->active)
- __pm_stay_awake(ep->ws);
- __pm_relax(epi->ws);
+ ws = ep_wakeup_source(epi);
+ if (ws) {
+ if (ws->active)
+ __pm_stay_awake(ep->ws);
+ __pm_relax(ws);
+ }
+
list_del_init(&epi->rdllink);
- pt._key = epi->event.events;
- revents = epi->ffd.file->f_op->poll(epi->ffd.file, &pt) &
- epi->event.events;
+ revents = ep_item_poll(epi, &pt);
/*
* If the event mask intersect the caller-requested one,
@@ -1376,7 +1484,7 @@ static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head,
if (__put_user(revents, &uevent->events) ||
__put_user(epi->event.data, &uevent->data)) {
list_add(&epi->rdllink, head);
- __pm_stay_awake(epi->ws);
+ ep_pm_stay_awake(epi);
return eventcnt ? eventcnt : -EFAULT;
}
eventcnt++;
@@ -1396,7 +1504,7 @@ static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head,
* poll callback will queue them in ep->ovflist.
*/
list_add_tail(&epi->rdllink, &ep->rdllist);
- __pm_stay_awake(epi->ws);
+ ep_pm_stay_awake(epi);
}
}
}
@@ -1495,7 +1603,8 @@ fetch_events:
}
spin_unlock_irqrestore(&ep->lock, flags);
- if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS))
+ if (!freezable_schedule_hrtimeout_range(to, slack,
+ HRTIMER_MODE_ABS))
timed_out = 1;
spin_lock_irqsave(&ep->lock, flags);
@@ -1654,8 +1763,8 @@ SYSCALL_DEFINE1(epoll_create1, int, flags)
error = PTR_ERR(file);
goto out_free_fd;
}
- fd_install(fd, file);
ep->file = file;
+ fd_install(fd, file);
return fd;
out_free_fd:
@@ -1710,7 +1819,7 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
goto error_tgt_fput;
/* Check if EPOLLWAKEUP is allowed */
- if ((epds.events & EPOLLWAKEUP) && !capable(CAP_EPOLLWAKEUP))
+ if ((epds.events & EPOLLWAKEUP) && !capable(CAP_BLOCK_SUSPEND))
epds.events &= ~EPOLLWAKEUP;
/*
@@ -1810,7 +1919,7 @@ SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events,
int, maxevents, int, timeout)
{
int error;
- struct file *file;
+ struct fd f;
struct eventpoll *ep;
/* The maximum number of event must be greater than zero */
@@ -1818,38 +1927,33 @@ SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events,
return -EINVAL;
/* Verify that the area passed by the user is writeable */
- if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event))) {
- error = -EFAULT;
- goto error_return;
- }
+ if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event)))
+ return -EFAULT;
/* Get the "struct file *" for the eventpoll file */
- error = -EBADF;
- file = fget(epfd);
- if (!file)
- goto error_return;
+ f = fdget(epfd);
+ if (!f.file)
+ return -EBADF;
/*
* We have to check that the file structure underneath the fd
* the user passed to us _is_ an eventpoll file.
*/
error = -EINVAL;
- if (!is_file_epoll(file))
+ if (!is_file_epoll(f.file))
goto error_fput;
/*
* At this point it is safe to assume that the "private_data" contains
* our own data structure.
*/
- ep = file->private_data;
+ ep = f.file->private_data;
/* Time to fish for events ... */
error = ep_poll(ep, events, maxevents, timeout);
error_fput:
- fput(file);
-error_return:
-
+ fdput(f);
return error;
}
@@ -1873,8 +1977,8 @@ SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events,
return -EINVAL;
if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
return -EFAULT;
- sigdelsetmask(&ksigmask, sigmask(SIGKILL) | sigmask(SIGSTOP));
- sigprocmask(SIG_SETMASK, &ksigmask, &sigsaved);
+ sigsaved = current->blocked;
+ set_current_blocked(&ksigmask);
}
error = sys_epoll_wait(epfd, events, maxevents, timeout);
@@ -1891,12 +1995,58 @@ SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events,
sizeof(sigsaved));
set_restore_sigmask();
} else
- sigprocmask(SIG_SETMASK, &sigsaved, NULL);
+ set_current_blocked(&sigsaved);
}
return error;
}
+#ifdef CONFIG_COMPAT
+COMPAT_SYSCALL_DEFINE6(epoll_pwait, int, epfd,
+ struct epoll_event __user *, events,
+ int, maxevents, int, timeout,
+ const compat_sigset_t __user *, sigmask,
+ compat_size_t, sigsetsize)
+{
+ long err;
+ compat_sigset_t csigmask;
+ sigset_t ksigmask, sigsaved;
+
+ /*
+ * If the caller wants a certain signal mask to be set during the wait,
+ * we apply it here.
+ */
+ if (sigmask) {
+ if (sigsetsize != sizeof(compat_sigset_t))
+ return -EINVAL;
+ if (copy_from_user(&csigmask, sigmask, sizeof(csigmask)))
+ return -EFAULT;
+ sigset_from_compat(&ksigmask, &csigmask);
+ sigsaved = current->blocked;
+ set_current_blocked(&ksigmask);
+ }
+
+ err = sys_epoll_wait(epfd, events, maxevents, timeout);
+
+ /*
+ * If we changed the signal mask, we need to restore the original one.
+ * In case we've got a signal while waiting, we do not restore the
+ * signal mask yet, and we allow do_signal() to deliver the signal on
+ * the way back to userspace, before the signal mask is restored.
+ */
+ if (sigmask) {
+ if (err == -EINTR) {
+ memcpy(&current->saved_sigmask, &sigsaved,
+ sizeof(sigsaved));
+ set_restore_sigmask();
+ } else
+ set_current_blocked(&sigsaved);
+ }
+
+ return err;
+}
+#endif
+
static int __init eventpoll_init(void)
{
struct sysinfo si;
@@ -1921,6 +2071,12 @@ static int __init eventpoll_init(void)
/* Initialize the structure used to perform file's f_op->poll() calls */
ep_nested_calls_init(&poll_readywalk_ncalls);
+ /*
+ * We can have many thousands of epitems, so prevent this from
+ * using an extra cache line on 64-bit (and smaller) CPUs
+ */
+ BUILD_BUG_ON(sizeof(void *) <= 8 && sizeof(struct epitem) > 128);
+
/* Allocates slab cache used to allocate "struct epitem" items */
epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem),
0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
generated by cgit v1.2.3 (git 2.39.1) at 2024-07-17 12:09:20 +0000