diff options
Diffstat (limited to 'ioq.c')
| -rw-r--r-- | ioq.c | 56 |
1 files changed, 46 insertions, 10 deletions
@@ -3,13 +3,41 @@ * License: GPLv3 or later (see COPYING for details) */ #include "cmogstored.h" +#include "trace.h" /* * This is a semaphore-like API with explicit queueing and activation, * so contended scheduling/wakeups happen via epoll/kqueue and there - * is never blocking of threads (other than the mutex) + * is never blocking of threads (other than the mutex which only protects + * small memory-only operations) * * The main operations are mog_ioq_ready and mog_ioq_next * + * Flow: + * + * mog_ioq_ready ---> true --> normal dispatch --> mog_ioq_next + * | ^ (mog_ioq_unblock) | + * | | | + * | `-------<--------\ | + * false | | + * | | V + * | | | + * V | | + * SIMPLEQ_INSERT_TAIL(push) ^ | + * || | V + * VV | / + * \\ | / + * \\ | / + * \\ | V + * `===(wait for)==========>===> SIMPLEQ_{FIRST,REMOVE_HEAD}(pop) + * | | + * | V + * | | + * ^ add to kqueue/epoll ready list + * | | + * | V + * | / + * `---------<---------' + * * mog_ioq_next is automatically called when releases a regular file. */ __thread struct mog_ioq *mog_ioq_current; @@ -53,9 +81,9 @@ static inline void ioq_set_contended(struct mog_ioq *ioq) * Adding the mfd to an epoll/kqueue watch list in the same thread/context * where this function returns true is a guaranteed bug. * - * client_mfd is the client socket, not the open (regular) file + * mfd is the client socket, not the open (regular) file */ -bool mog_ioq_ready(struct mog_ioq *ioq, struct mog_fd *client_mfd) +bool mog_ioq_ready(struct mog_ioq *ioq, struct mog_fd *mfd) { bool good; @@ -73,8 +101,8 @@ bool mog_ioq_ready(struct mog_ioq *ioq, struct mog_fd *client_mfd) mog_ioq_current = ioq; } else { - client_mfd->ioq_blocked = 1; - SIMPLEQ_INSERT_TAIL(&ioq->ioq_head, client_mfd, ioqent); + mfd->ioq_blocked = 1; + SIMPLEQ_INSERT_TAIL(&ioq->ioq_head, mfd, ioqent); ioq_set_contended(ioq); } @@ -89,7 +117,7 @@ bool mog_ioq_ready(struct mog_ioq *ioq, struct mog_fd *client_mfd) */ void mog_ioq_next(struct mog_ioq *check_ioq) { - struct mog_fd *client_mfd = NULL; + struct mog_fd *mfd = NULL; if (mog_ioq_current == NULL) return; @@ -102,8 +130,8 @@ void mog_ioq_next(struct mog_ioq *check_ioq) mog_ioq_current->cur++; if (mog_ioq_current->cur <= mog_ioq_current->max) { /* wake up any waiters */ - client_mfd = SIMPLEQ_FIRST(&mog_ioq_current->ioq_head); - if (client_mfd) { + mfd = SIMPLEQ_FIRST(&mog_ioq_current->ioq_head); + if (mfd) { SIMPLEQ_REMOVE_HEAD(&mog_ioq_current->ioq_head, ioqent); /* if there's another head, we're still contended */ @@ -118,8 +146,10 @@ void mog_ioq_next(struct mog_ioq *check_ioq) CHECK(int, 0, pthread_mutex_unlock(&mog_ioq_current->mtx)); /* wake up the next sleeper on this queue */ - if (client_mfd) - mog_activeq_push(mog_ioq_current->svc->queue, client_mfd); + if (mfd) { + TRACE(CMOGSTORED_IOQ_RESCHEDULE(mfd->fd)); + mog_activeq_push(mog_ioq_current->svc->queue, mfd); + } /* * We may not touch or use client_mfd here anymore. Another * thread may already have it. In the worst case, it's been @@ -173,6 +203,12 @@ void mog_ioq_destroy(struct mog_ioq *ioq) CHECK(int, 0, pthread_mutex_destroy(&ioq->mtx)); } +/* + * If this returns true, the caller must continue processing a request + * without checking other state associated with the mfd. + * If this returns false (the common case), the caller continues as + * usual. + */ bool mog_ioq_unblock(struct mog_fd *mfd) { if (mfd->ioq_blocked == 0) |