2011-01-17 17:08:14 +01:00
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/*
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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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2011-06-30 17:56:46 +02:00
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* Kevin Wolf <kwolf@redhat.com>
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2011-01-17 17:08:14 +01:00
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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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2012-12-17 18:20:00 +01:00
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#include "qemu/queue.h"
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#include "qemu/timer.h"
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2011-01-17 17:08:14 +01:00
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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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coroutine: move entry argument to qemu_coroutine_create
In practice the entry argument is always known at creation time, and
it is confusing that sometimes qemu_coroutine_enter is used with a
non-NULL argument to re-enter a coroutine (this happens in
block/sheepdog.c and tests/test-coroutine.c). So pass the opaque value
at creation time, for consistency with e.g. aio_bh_new.
Mostly done with the following semantic patch:
@ entry1 @
expression entry, arg, co;
@@
- co = qemu_coroutine_create(entry);
+ co = qemu_coroutine_create(entry, arg);
...
- qemu_coroutine_enter(co, arg);
+ qemu_coroutine_enter(co);
@ entry2 @
expression entry, arg;
identifier co;
@@
- Coroutine *co = qemu_coroutine_create(entry);
+ Coroutine *co = qemu_coroutine_create(entry, arg);
...
- qemu_coroutine_enter(co, arg);
+ qemu_coroutine_enter(co);
@ entry3 @
expression entry, arg;
@@
- qemu_coroutine_enter(qemu_coroutine_create(entry), arg);
+ qemu_coroutine_enter(qemu_coroutine_create(entry, arg));
@ reentry @
expression co;
@@
- qemu_coroutine_enter(co, NULL);
+ qemu_coroutine_enter(co);
except for the aforementioned few places where the semantic patch
stumbled (as expected) and for test_co_queue, which would otherwise
produce an uninitialized variable warning.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2016-07-04 19:10:01 +02:00
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* The opaque argument is passed as the argument to the entry point.
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2011-01-17 17:08:14 +01:00
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*/
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coroutine: move entry argument to qemu_coroutine_create
In practice the entry argument is always known at creation time, and
it is confusing that sometimes qemu_coroutine_enter is used with a
non-NULL argument to re-enter a coroutine (this happens in
block/sheepdog.c and tests/test-coroutine.c). So pass the opaque value
at creation time, for consistency with e.g. aio_bh_new.
Mostly done with the following semantic patch:
@ entry1 @
expression entry, arg, co;
@@
- co = qemu_coroutine_create(entry);
+ co = qemu_coroutine_create(entry, arg);
...
- qemu_coroutine_enter(co, arg);
+ qemu_coroutine_enter(co);
@ entry2 @
expression entry, arg;
identifier co;
@@
- Coroutine *co = qemu_coroutine_create(entry);
+ Coroutine *co = qemu_coroutine_create(entry, arg);
...
- qemu_coroutine_enter(co, arg);
+ qemu_coroutine_enter(co);
@ entry3 @
expression entry, arg;
@@
- qemu_coroutine_enter(qemu_coroutine_create(entry), arg);
+ qemu_coroutine_enter(qemu_coroutine_create(entry, arg));
@ reentry @
expression co;
@@
- qemu_coroutine_enter(co, NULL);
+ qemu_coroutine_enter(co);
except for the aforementioned few places where the semantic patch
stumbled (as expected) and for test_co_queue, which would otherwise
produce an uninitialized variable warning.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2016-07-04 19:10:01 +02:00
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Coroutine *qemu_coroutine_create(CoroutineEntry *entry, void *opaque);
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2011-01-17 17:08:14 +01:00
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/**
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* Transfer control to a coroutine
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*/
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coroutine: move entry argument to qemu_coroutine_create
In practice the entry argument is always known at creation time, and
it is confusing that sometimes qemu_coroutine_enter is used with a
non-NULL argument to re-enter a coroutine (this happens in
block/sheepdog.c and tests/test-coroutine.c). So pass the opaque value
at creation time, for consistency with e.g. aio_bh_new.
Mostly done with the following semantic patch:
@ entry1 @
expression entry, arg, co;
@@
- co = qemu_coroutine_create(entry);
+ co = qemu_coroutine_create(entry, arg);
...
- qemu_coroutine_enter(co, arg);
+ qemu_coroutine_enter(co);
@ entry2 @
expression entry, arg;
identifier co;
@@
- Coroutine *co = qemu_coroutine_create(entry);
+ Coroutine *co = qemu_coroutine_create(entry, arg);
...
- qemu_coroutine_enter(co, arg);
+ qemu_coroutine_enter(co);
@ entry3 @
expression entry, arg;
@@
- qemu_coroutine_enter(qemu_coroutine_create(entry), arg);
+ qemu_coroutine_enter(qemu_coroutine_create(entry, arg));
@ reentry @
expression co;
@@
- qemu_coroutine_enter(co, NULL);
+ qemu_coroutine_enter(co);
except for the aforementioned few places where the semantic patch
stumbled (as expected) and for test_co_queue, which would otherwise
produce an uninitialized variable warning.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2016-07-04 19:10:01 +02:00
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void qemu_coroutine_enter(Coroutine *coroutine);
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2011-01-17 17:08:14 +01:00
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2016-11-07 16:34:35 +01:00
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/**
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* Transfer control to a coroutine if it's not active (i.e. part of the call
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* stack of the running coroutine). Otherwise, do nothing.
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*/
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void qemu_coroutine_enter_if_inactive(Coroutine *co);
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2011-01-17 17:08:14 +01:00
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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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2016-09-27 17:18:34 +02:00
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/**
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* Return true if the coroutine is currently entered
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*
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* A coroutine is "entered" if it has not yielded from the current
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* qemu_coroutine_enter() call used to run it. This does not mean that the
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* coroutine is currently executing code since it may have transferred control
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* to another coroutine using qemu_coroutine_enter().
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*
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* When several coroutines enter each other there may be no way to know which
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* ones have already been entered. In such situations this function can be
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* used to avoid recursively entering coroutines.
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*/
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bool qemu_coroutine_entered(Coroutine *co);
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2011-06-30 17:56:46 +02:00
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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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2017-02-13 19:12:39 +01:00
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struct CoWaitRecord;
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2011-06-30 17:56:46 +02:00
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typedef struct CoMutex {
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2017-02-13 19:12:39 +01:00
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/* Count of pending lockers; 0 for a free mutex, 1 for an
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* uncontended mutex.
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*/
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unsigned locked;
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2017-02-13 19:12:40 +01:00
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/* Context that is holding the lock. Useful to avoid spinning
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* when two coroutines on the same AioContext try to get the lock. :)
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*/
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AioContext *ctx;
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2017-02-13 19:12:39 +01:00
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/* A queue of waiters. Elements are added atomically in front of
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* from_push. to_pop is only populated, and popped from, by whoever
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* is in charge of the next wakeup. This can be an unlocker or,
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* through the handoff protocol, a locker that is about to go to sleep.
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*/
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QSLIST_HEAD(, CoWaitRecord) from_push, to_pop;
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unsigned handoff, sequence;
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2016-08-11 17:45:06 +02:00
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Coroutine *holder;
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2011-06-30 17:56:46 +02:00
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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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2017-02-13 19:12:42 +01:00
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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.
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*/
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typedef struct CoQueue {
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QSIMPLEQ_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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2011-08-02 08:32:51 +02:00
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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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2013-10-24 09:01:14 +02:00
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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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2014-07-07 15:18:02 +02:00
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* resumed when using aio_poll().
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2013-10-24 09:01:14 +02:00
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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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2013-06-26 03:35:29 +02:00
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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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2014-07-07 15:15:52 +02:00
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2011-01-17 17:08:14 +01:00
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#endif /* QEMU_COROUTINE_H */
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