block_job_sleep_ns is the only user. Since we are moving towards AioContext aware code, it's better to use the explicit version and drop the old one. Signed-off-by: Fam Zheng <famz@redhat.com> Reviewed-by: Benoît Canet <benoit.canet@nodalink.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
230 lines
6.1 KiB
C
230 lines
6.1 KiB
C
/*
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* QEMU coroutine implementation
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*
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* Copyright IBM, Corp. 2011
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*
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* Authors:
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* Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
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* Kevin Wolf <kwolf@redhat.com>
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*
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* This work is licensed under the terms of the GNU LGPL, version 2 or later.
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* See the COPYING.LIB file in the top-level directory.
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*
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*/
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#ifndef QEMU_COROUTINE_H
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#define QEMU_COROUTINE_H
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#include <stdbool.h>
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#include "qemu/typedefs.h"
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#include "qemu/queue.h"
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#include "qemu/timer.h"
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/**
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* Coroutines are a mechanism for stack switching and can be used for
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* cooperative userspace threading. These functions provide a simple but
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* useful flavor of coroutines that is suitable for writing sequential code,
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* rather than callbacks, for operations that need to give up control while
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* waiting for events to complete.
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*
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* These functions are re-entrant and may be used outside the global mutex.
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*/
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/**
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* Mark a function that executes in coroutine context
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*
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* Functions that execute in coroutine context cannot be called directly from
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* normal functions. In the future it would be nice to enable compiler or
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* static checker support for catching such errors. This annotation might make
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* it possible and in the meantime it serves as documentation.
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*
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* For example:
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*
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* static void coroutine_fn foo(void) {
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* ....
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* }
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*/
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#define coroutine_fn
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typedef struct Coroutine Coroutine;
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/**
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* Coroutine entry point
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*
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* When the coroutine is entered for the first time, opaque is passed in as an
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* argument.
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*
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* When this function returns, the coroutine is destroyed automatically and
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* execution continues in the caller who last entered the coroutine.
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*/
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typedef void coroutine_fn CoroutineEntry(void *opaque);
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/**
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* Create a new coroutine
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*
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* Use qemu_coroutine_enter() to actually transfer control to the coroutine.
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*/
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Coroutine *qemu_coroutine_create(CoroutineEntry *entry);
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/**
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* Transfer control to a coroutine
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*
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* The opaque argument is passed as the argument to the entry point when
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* entering the coroutine for the first time. It is subsequently ignored.
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*/
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void qemu_coroutine_enter(Coroutine *coroutine, void *opaque);
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/**
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* Transfer control back to a coroutine's caller
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*
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* This function does not return until the coroutine is re-entered using
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* qemu_coroutine_enter().
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*/
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void coroutine_fn qemu_coroutine_yield(void);
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/**
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* Get the currently executing coroutine
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*/
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Coroutine *coroutine_fn qemu_coroutine_self(void);
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/**
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* Return whether or not currently inside a coroutine
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*
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* This can be used to write functions that work both when in coroutine context
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* and when not in coroutine context. Note that such functions cannot use the
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* coroutine_fn annotation since they work outside coroutine context.
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*/
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bool qemu_in_coroutine(void);
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/**
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* CoQueues are a mechanism to queue coroutines in order to continue executing
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* them later. They provide the fundamental primitives on which coroutine locks
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* are built.
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*/
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typedef struct CoQueue {
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QTAILQ_HEAD(, Coroutine) entries;
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} CoQueue;
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/**
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* Initialise a CoQueue. This must be called before any other operation is used
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* on the CoQueue.
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*/
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void qemu_co_queue_init(CoQueue *queue);
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/**
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* Adds the current coroutine to the CoQueue and transfers control to the
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* caller of the coroutine.
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*/
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void coroutine_fn qemu_co_queue_wait(CoQueue *queue);
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/**
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* Restarts the next coroutine in the CoQueue and removes it from the queue.
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*
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* Returns true if a coroutine was restarted, false if the queue is empty.
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*/
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bool coroutine_fn qemu_co_queue_next(CoQueue *queue);
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/**
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* Restarts all coroutines in the CoQueue and leaves the queue empty.
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*/
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void coroutine_fn qemu_co_queue_restart_all(CoQueue *queue);
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/**
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* Enter the next coroutine in the queue
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*/
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bool qemu_co_enter_next(CoQueue *queue);
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/**
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* Checks if the CoQueue is empty.
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*/
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bool qemu_co_queue_empty(CoQueue *queue);
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/**
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* Provides a mutex that can be used to synchronise coroutines
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*/
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typedef struct CoMutex {
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bool locked;
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CoQueue queue;
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} CoMutex;
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/**
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* Initialises a CoMutex. This must be called before any other operation is used
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* on the CoMutex.
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*/
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void qemu_co_mutex_init(CoMutex *mutex);
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/**
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* Locks the mutex. If the lock cannot be taken immediately, control is
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* transferred to the caller of the current coroutine.
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*/
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void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex);
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/**
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* Unlocks the mutex and schedules the next coroutine that was waiting for this
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* lock to be run.
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*/
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void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex);
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typedef struct CoRwlock {
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bool writer;
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int reader;
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CoQueue queue;
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} CoRwlock;
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/**
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* Initialises a CoRwlock. This must be called before any other operation
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* is used on the CoRwlock
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*/
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void qemu_co_rwlock_init(CoRwlock *lock);
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/**
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* Read locks the CoRwlock. If the lock cannot be taken immediately because
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* of a parallel writer, control is transferred to the caller of the current
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* coroutine.
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*/
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void qemu_co_rwlock_rdlock(CoRwlock *lock);
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/**
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* Write Locks the mutex. If the lock cannot be taken immediately because
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* of a parallel reader, control is transferred to the caller of the current
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* coroutine.
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*/
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void qemu_co_rwlock_wrlock(CoRwlock *lock);
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/**
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* Unlocks the read/write lock and schedules the next coroutine that was
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* waiting for this lock to be run.
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*/
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void qemu_co_rwlock_unlock(CoRwlock *lock);
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/**
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* Yield the coroutine for a given duration
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*
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* Behaves similarly to co_sleep_ns(), but the sleeping coroutine will be
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* resumed when using aio_poll().
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*/
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void coroutine_fn co_aio_sleep_ns(AioContext *ctx, QEMUClockType type,
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int64_t ns);
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/**
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* Yield until a file descriptor becomes readable
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*
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* Note that this function clobbers the handlers for the file descriptor.
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*/
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void coroutine_fn yield_until_fd_readable(int fd);
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/**
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* Add or subtract from the coroutine pool size
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*
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* The coroutine implementation keeps a pool of coroutines to be reused by
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* qemu_coroutine_create(). This makes coroutine creation cheap. Heavy
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* coroutine users should call this to reserve pool space. Call it again with
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* a negative number to release pool space.
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*/
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void qemu_coroutine_adjust_pool_size(int n);
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#endif /* QEMU_COROUTINE_H */
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