forked from luck/tmp_suning_uos_patched
epoll locks changes and cleanups
Changes the rwlock to a spinlock, and drops the use-count variable. Operations are always bound by the mutex now, so the use-count is no more needed. For the same reason, the rwlock can become a simple spinlock. Signed-off-by: Davide Libenzi <davidel@xmailserver.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Davide Libenzi
Linus Torvalds
parent
d47de16c72
commit
c7ea763025
232
fs/eventpoll.c
232
fs/eventpoll.c
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@ -1,6 +1,6 @@
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/*
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* fs/eventpoll.c ( Efficent event polling implementation )
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* Copyright (C) 2001,...,2006 Davide Libenzi
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* fs/eventpoll.c (Efficent event polling implementation)
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* Copyright (C) 2001,...,2007 Davide Libenzi
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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@ -44,8 +44,8 @@
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* There are three level of locking required by epoll :
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*
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* 1) epmutex (mutex)
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* 2) ep->mtx (mutes)
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* 3) ep->lock (rw_lock)
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* 2) ep->mtx (mutex)
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* 3) ep->lock (spinlock)
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*
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* The acquire order is the one listed above, from 1 to 3.
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* We need a spinlock (ep->lock) because we manipulate objects
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@ -140,6 +140,12 @@ struct epitem {
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/* List header used to link this structure to the eventpoll ready list */
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struct list_head rdllink;
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/*
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* Works together "struct eventpoll"->ovflist in keeping the
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* single linked chain of items.
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*/
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struct epitem *next;
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/* The file descriptor information this item refers to */
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struct epoll_filefd ffd;
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@ -152,23 +158,11 @@ struct epitem {
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/* The "container" of this item */
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struct eventpoll *ep;
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/* The structure that describe the interested events and the source fd */
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struct epoll_event event;
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/*
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* Used to keep track of the usage count of the structure. This avoids
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* that the structure will desappear from underneath our processing.
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*/
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atomic_t usecnt;
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/* List header used to link this item to the "struct file" items list */
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struct list_head fllink;
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/*
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* Works together "struct eventpoll"->ovflist in keeping the
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* single linked chain of items.
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*/
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struct epitem *next;
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/* The structure that describe the interested events and the source fd */
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struct epoll_event event;
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};
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/*
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@ -178,7 +172,7 @@ struct epitem {
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*/
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struct eventpoll {
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/* Protect the this structure access */
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rwlock_t lock;
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spinlock_t lock;
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/*
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* This mutex is used to ensure that files are not removed
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@ -393,79 +387,12 @@ static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi)
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}
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}
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/*
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* Unlink the "struct epitem" from all places it might have been hooked up.
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* This function must be called with write IRQ lock on "ep->lock".
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*/
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static int ep_unlink(struct eventpoll *ep, struct epitem *epi)
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{
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int error;
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/*
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* It can happen that this one is called for an item already unlinked.
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* The check protect us from doing a double unlink ( crash ).
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*/
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error = -ENOENT;
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if (!ep_rb_linked(&epi->rbn))
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goto error_return;
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/*
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* Clear the event mask for the unlinked item. This will avoid item
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* notifications to be sent after the unlink operation from inside
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* the kernel->userspace event transfer loop.
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*/
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epi->event.events = 0;
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/*
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* At this point is safe to do the job, unlink the item from our rb-tree.
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* This operation togheter with the above check closes the door to
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* double unlinks.
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*/
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ep_rb_erase(&epi->rbn, &ep->rbr);
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/*
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* If the item we are going to remove is inside the ready file descriptors
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* we want to remove it from this list to avoid stale events.
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*/
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if (ep_is_linked(&epi->rdllink))
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list_del_init(&epi->rdllink);
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error = 0;
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error_return:
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DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_unlink(%p, %p) = %d\n",
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current, ep, epi->ffd.file, error));
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return error;
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}
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/*
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* Increment the usage count of the "struct epitem" making it sure
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* that the user will have a valid pointer to reference.
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*/
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static void ep_use_epitem(struct epitem *epi)
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{
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atomic_inc(&epi->usecnt);
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}
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/*
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* Decrement ( release ) the usage count by signaling that the user
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* has finished using the structure. It might lead to freeing the
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* structure itself if the count goes to zero.
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*/
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static void ep_release_epitem(struct epitem *epi)
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{
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if (atomic_dec_and_test(&epi->usecnt))
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kmem_cache_free(epi_cache, epi);
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}
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/*
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* Removes a "struct epitem" from the eventpoll RB tree and deallocates
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* all the associated resources.
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* all the associated resources. Must be called with "mtx" held.
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*/
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static int ep_remove(struct eventpoll *ep, struct epitem *epi)
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{
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int error;
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unsigned long flags;
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struct file *file = epi->ffd.file;
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@ -485,26 +412,21 @@ static int ep_remove(struct eventpoll *ep, struct epitem *epi)
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list_del_init(&epi->fllink);
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spin_unlock(&file->f_ep_lock);
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/* We need to acquire the write IRQ lock before calling ep_unlink() */
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write_lock_irqsave(&ep->lock, flags);
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if (ep_rb_linked(&epi->rbn))
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ep_rb_erase(&epi->rbn, &ep->rbr);
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/* Really unlink the item from the RB tree */
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error = ep_unlink(ep, epi);
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write_unlock_irqrestore(&ep->lock, flags);
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if (error)
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goto error_return;
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spin_lock_irqsave(&ep->lock, flags);
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if (ep_is_linked(&epi->rdllink))
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list_del_init(&epi->rdllink);
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spin_unlock_irqrestore(&ep->lock, flags);
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/* At this point it is safe to free the eventpoll item */
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ep_release_epitem(epi);
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kmem_cache_free(epi_cache, epi);
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error = 0;
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error_return:
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DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_remove(%p, %p) = %d\n",
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current, ep, file, error));
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DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_remove(%p, %p)\n",
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current, ep, file));
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return error;
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return 0;
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}
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static void ep_free(struct eventpoll *ep)
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@ -574,10 +496,10 @@ static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait)
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poll_wait(file, &ep->poll_wait, wait);
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/* Check our condition */
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read_lock_irqsave(&ep->lock, flags);
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spin_lock_irqsave(&ep->lock, flags);
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if (!list_empty(&ep->rdllist))
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pollflags = POLLIN | POLLRDNORM;
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read_unlock_irqrestore(&ep->lock, flags);
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spin_unlock_irqrestore(&ep->lock, flags);
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return pollflags;
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}
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@ -636,7 +558,7 @@ static int ep_alloc(struct eventpoll **pep)
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if (!ep)
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return -ENOMEM;
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rwlock_init(&ep->lock);
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spin_lock_init(&ep->lock);
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mutex_init(&ep->mtx);
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init_waitqueue_head(&ep->wq);
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init_waitqueue_head(&ep->poll_wait);
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@ -652,20 +574,18 @@ static int ep_alloc(struct eventpoll **pep)
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}
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/*
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* Search the file inside the eventpoll tree. It add usage count to
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* the returned item, so the caller must call ep_release_epitem()
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* after finished using the "struct epitem".
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* Search the file inside the eventpoll tree. The RB tree operations
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* are protected by the "mtx" mutex, and ep_find() must be called with
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* "mtx" held.
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*/
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static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd)
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{
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int kcmp;
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unsigned long flags;
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struct rb_node *rbp;
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struct epitem *epi, *epir = NULL;
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struct epoll_filefd ffd;
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ep_set_ffd(&ffd, file, fd);
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read_lock_irqsave(&ep->lock, flags);
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for (rbp = ep->rbr.rb_node; rbp; ) {
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epi = rb_entry(rbp, struct epitem, rbn);
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kcmp = ep_cmp_ffd(&ffd, &epi->ffd);
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@ -674,12 +594,10 @@ static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd)
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else if (kcmp < 0)
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rbp = rbp->rb_left;
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else {
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ep_use_epitem(epi);
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epir = epi;
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break;
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}
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}
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read_unlock_irqrestore(&ep->lock, flags);
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DNPRINTK(3, (KERN_INFO "[%p] eventpoll: ep_find(%p) -> %p\n",
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current, file, epir));
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@ -702,7 +620,7 @@ static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *k
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DNPRINTK(3, (KERN_INFO "[%p] eventpoll: poll_callback(%p) epi=%p ep=%p\n",
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current, epi->ffd.file, epi, ep));
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write_lock_irqsave(&ep->lock, flags);
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spin_lock_irqsave(&ep->lock, flags);
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/*
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* If the event mask does not contain any poll(2) event, we consider the
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@ -745,7 +663,7 @@ static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *k
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pwake++;
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out_unlock:
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write_unlock_irqrestore(&ep->lock, flags);
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spin_unlock_irqrestore(&ep->lock, flags);
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/* We have to call this outside the lock */
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if (pwake)
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@ -796,6 +714,9 @@ static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi)
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rb_insert_color(&epi->rbn, &ep->rbr);
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}
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/*
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* Must be called with "mtx" held.
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*/
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static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
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struct file *tfile, int fd)
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{
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@ -816,7 +737,6 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
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epi->ep = ep;
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ep_set_ffd(&epi->ffd, tfile, fd);
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epi->event = *event;
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atomic_set(&epi->usecnt, 1);
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epi->nwait = 0;
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epi->next = EP_UNACTIVE_PTR;
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@ -827,7 +747,9 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
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/*
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* Attach the item to the poll hooks and get current event bits.
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* We can safely use the file* here because its usage count has
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* been increased by the caller of this function.
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* been increased by the caller of this function. Note that after
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* this operation completes, the poll callback can start hitting
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* the new item.
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*/
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revents = tfile->f_op->poll(tfile, &epq.pt);
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@ -844,12 +766,15 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
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list_add_tail(&epi->fllink, &tfile->f_ep_links);
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spin_unlock(&tfile->f_ep_lock);
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/* We have to drop the new item inside our item list to keep track of it */
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write_lock_irqsave(&ep->lock, flags);
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/* Add the current item to the rb-tree */
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/*
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* Add the current item to the RB tree. All RB tree operations are
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* protected by "mtx", and ep_insert() is called with "mtx" held.
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*/
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ep_rbtree_insert(ep, epi);
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/* We have to drop the new item inside our item list to keep track of it */
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spin_lock_irqsave(&ep->lock, flags);
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/* If the file is already "ready" we drop it inside the ready list */
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if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) {
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list_add_tail(&epi->rdllink, &ep->rdllist);
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@ -861,7 +786,7 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
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pwake++;
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}
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write_unlock_irqrestore(&ep->lock, flags);
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spin_unlock_irqrestore(&ep->lock, flags);
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/* We have to call this outside the lock */
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if (pwake)
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@ -879,10 +804,10 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
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* We need to do this because an event could have been arrived on some
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* allocated wait queue.
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*/
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write_lock_irqsave(&ep->lock, flags);
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spin_lock_irqsave(&ep->lock, flags);
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if (ep_is_linked(&epi->rdllink))
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list_del_init(&epi->rdllink);
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write_unlock_irqrestore(&ep->lock, flags);
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spin_unlock_irqrestore(&ep->lock, flags);
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kmem_cache_free(epi_cache, epi);
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error_return:
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@ -891,7 +816,7 @@ static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
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/*
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* Modify the interest event mask by dropping an event if the new mask
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* has a match in the current file status.
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* has a match in the current file status. Must be called with "mtx" held.
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*/
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static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event)
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{
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@ -913,36 +838,29 @@ static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_even
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*/
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revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL);
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write_lock_irqsave(&ep->lock, flags);
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spin_lock_irqsave(&ep->lock, flags);
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/* Copy the data member from inside the lock */
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epi->event.data = event->data;
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/*
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* If the item is not linked to the RB tree it means that it's on its
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* way toward the removal. Do nothing in this case.
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* If the item is "hot" and it is not registered inside the ready
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* list, push it inside. If the item is not "hot" and it is currently
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* registered inside the ready list, unlink it.
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*/
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if (ep_rb_linked(&epi->rbn)) {
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/*
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* If the item is "hot" and it is not registered inside the ready
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* list, push it inside. If the item is not "hot" and it is currently
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* registered inside the ready list, unlink it.
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*/
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if (revents & event->events) {
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if (!ep_is_linked(&epi->rdllink)) {
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list_add_tail(&epi->rdllink, &ep->rdllist);
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if (revents & event->events) {
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if (!ep_is_linked(&epi->rdllink)) {
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list_add_tail(&epi->rdllink, &ep->rdllist);
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/* Notify waiting tasks that events are available */
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if (waitqueue_active(&ep->wq))
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__wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE |
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TASK_INTERRUPTIBLE);
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if (waitqueue_active(&ep->poll_wait))
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pwake++;
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}
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/* Notify waiting tasks that events are available */
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if (waitqueue_active(&ep->wq))
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__wake_up_locked(&ep->wq, TASK_UNINTERRUPTIBLE |
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TASK_INTERRUPTIBLE);
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if (waitqueue_active(&ep->poll_wait))
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pwake++;
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}
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}
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write_unlock_irqrestore(&ep->lock, flags);
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spin_unlock_irqrestore(&ep->lock, flags);
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/* We have to call this outside the lock */
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if (pwake)
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@ -975,11 +893,11 @@ static int ep_send_events(struct eventpoll *ep, struct epoll_event __user *event
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* have the poll callback to queue directly on ep->rdllist,
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* because we are doing it in the loop below, in a lockless way.
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*/
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write_lock_irqsave(&ep->lock, flags);
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spin_lock_irqsave(&ep->lock, flags);
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list_splice(&ep->rdllist, &txlist);
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INIT_LIST_HEAD(&ep->rdllist);
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ep->ovflist = NULL;
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write_unlock_irqrestore(&ep->lock, flags);
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spin_unlock_irqrestore(&ep->lock, flags);
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/*
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* We can loop without lock because this is a task private list.
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@ -1028,7 +946,7 @@ static int ep_send_events(struct eventpoll *ep, struct epoll_event __user *event
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errxit:
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write_lock_irqsave(&ep->lock, flags);
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spin_lock_irqsave(&ep->lock, flags);
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/*
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* During the time we spent in the loop above, some other events
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* might have been queued by the poll callback. We re-insert them
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@ -1064,7 +982,7 @@ static int ep_send_events(struct eventpoll *ep, struct epoll_event __user *event
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if (waitqueue_active(&ep->poll_wait))
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pwake++;
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}
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write_unlock_irqrestore(&ep->lock, flags);
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spin_unlock_irqrestore(&ep->lock, flags);
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mutex_unlock(&ep->mtx);
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@ -1092,7 +1010,7 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
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MAX_SCHEDULE_TIMEOUT : (timeout * HZ + 999) / 1000;
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retry:
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write_lock_irqsave(&ep->lock, flags);
|
||||
spin_lock_irqsave(&ep->lock, flags);
|
||||
|
||||
res = 0;
|
||||
if (list_empty(&ep->rdllist)) {
|
||||
|
|
@ -1119,9 +1037,9 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
|
|||
break;
|
||||
}
|
||||
|
||||
write_unlock_irqrestore(&ep->lock, flags);
|
||||
spin_unlock_irqrestore(&ep->lock, flags);
|
||||
jtimeout = schedule_timeout(jtimeout);
|
||||
write_lock_irqsave(&ep->lock, flags);
|
||||
spin_lock_irqsave(&ep->lock, flags);
|
||||
}
|
||||
__remove_wait_queue(&ep->wq, &wait);
|
||||
|
||||
|
|
@ -1131,7 +1049,7 @@ static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
|
|||
/* Is it worth to try to dig for events ? */
|
||||
eavail = !list_empty(&ep->rdllist);
|
||||
|
||||
write_unlock_irqrestore(&ep->lock, flags);
|
||||
spin_unlock_irqrestore(&ep->lock, flags);
|
||||
|
||||
/*
|
||||
* Try to transfer events to user space. In case we get 0 events and
|
||||
|
|
@ -1276,12 +1194,6 @@ asmlinkage long sys_epoll_ctl(int epfd, int op, int fd,
|
|||
error = -ENOENT;
|
||||
break;
|
||||
}
|
||||
/*
|
||||
* The function ep_find() increments the usage count of the structure
|
||||
* so, if this is not NULL, we need to release it.
|
||||
*/
|
||||
if (epi)
|
||||
ep_release_epitem(epi);
|
||||
mutex_unlock(&ep->mtx);
|
||||
|
||||
error_tgt_fput:
|
||||
|
|
@ -1388,7 +1300,7 @@ asmlinkage long sys_epoll_pwait(int epfd, struct epoll_event __user *events,
|
|||
if (sigmask) {
|
||||
if (error == -EINTR) {
|
||||
memcpy(¤t->saved_sigmask, &sigsaved,
|
||||
sizeof(sigsaved));
|
||||
sizeof(sigsaved));
|
||||
set_thread_flag(TIF_RESTORE_SIGMASK);
|
||||
} else
|
||||
sigprocmask(SIG_SETMASK, &sigsaved, NULL);
|
||||
|
|
|
|||
Loading…
Reference in New Issue
Block a user