70c60c089f
The 'gthread' coroutine backend was written before the freelist (aka
pool) existed in qemu-coroutine.c.
This means that every thread is expected to exit when its coroutine
terminates. It is not possible to reuse threads from a pool.
This patch automatically disables the pool when 'gthread' is used. This
allows the 'gthread' backend to work again (for example,
tests/test-coroutine completes successfully instead of hanging).
I considered implementing thread reuse but I don't want quirks like CPU
affinity differences due to coroutine threads being recycled. The
'gthread' backend is a reference backend and it's therefore okay to skip
the pool optimization.
Note this patch also makes it easy to toggle the pool for benchmarking
purposes:
./configure --with-coroutine-backend=ucontext \
--disable-coroutine-pool
Reported-by: Gabriel Kerneis <gabriel@kerneis.info>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Gabriel Kerneis <gabriel@kerneis.info>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
140 lines
3.0 KiB
C
140 lines
3.0 KiB
C
/*
|
|
* QEMU coroutines
|
|
*
|
|
* Copyright IBM, Corp. 2011
|
|
*
|
|
* Authors:
|
|
* Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
|
|
* Kevin Wolf <kwolf@redhat.com>
|
|
*
|
|
* This work is licensed under the terms of the GNU LGPL, version 2 or later.
|
|
* See the COPYING.LIB file in the top-level directory.
|
|
*
|
|
*/
|
|
|
|
#include "trace.h"
|
|
#include "qemu-common.h"
|
|
#include "qemu/thread.h"
|
|
#include "block/coroutine.h"
|
|
#include "block/coroutine_int.h"
|
|
|
|
enum {
|
|
/* Maximum free pool size prevents holding too many freed coroutines */
|
|
POOL_MAX_SIZE = 64,
|
|
};
|
|
|
|
/** Free list to speed up creation */
|
|
static QemuMutex pool_lock;
|
|
static QSLIST_HEAD(, Coroutine) pool = QSLIST_HEAD_INITIALIZER(pool);
|
|
static unsigned int pool_size;
|
|
|
|
Coroutine *qemu_coroutine_create(CoroutineEntry *entry)
|
|
{
|
|
Coroutine *co = NULL;
|
|
|
|
if (CONFIG_COROUTINE_POOL) {
|
|
qemu_mutex_lock(&pool_lock);
|
|
co = QSLIST_FIRST(&pool);
|
|
if (co) {
|
|
QSLIST_REMOVE_HEAD(&pool, pool_next);
|
|
pool_size--;
|
|
}
|
|
qemu_mutex_unlock(&pool_lock);
|
|
}
|
|
|
|
if (!co) {
|
|
co = qemu_coroutine_new();
|
|
}
|
|
|
|
co->entry = entry;
|
|
QTAILQ_INIT(&co->co_queue_wakeup);
|
|
return co;
|
|
}
|
|
|
|
static void coroutine_delete(Coroutine *co)
|
|
{
|
|
if (CONFIG_COROUTINE_POOL) {
|
|
qemu_mutex_lock(&pool_lock);
|
|
if (pool_size < POOL_MAX_SIZE) {
|
|
QSLIST_INSERT_HEAD(&pool, co, pool_next);
|
|
co->caller = NULL;
|
|
pool_size++;
|
|
qemu_mutex_unlock(&pool_lock);
|
|
return;
|
|
}
|
|
qemu_mutex_unlock(&pool_lock);
|
|
}
|
|
|
|
qemu_coroutine_delete(co);
|
|
}
|
|
|
|
static void __attribute__((constructor)) coroutine_pool_init(void)
|
|
{
|
|
qemu_mutex_init(&pool_lock);
|
|
}
|
|
|
|
static void __attribute__((destructor)) coroutine_pool_cleanup(void)
|
|
{
|
|
Coroutine *co;
|
|
Coroutine *tmp;
|
|
|
|
QSLIST_FOREACH_SAFE(co, &pool, pool_next, tmp) {
|
|
QSLIST_REMOVE_HEAD(&pool, pool_next);
|
|
qemu_coroutine_delete(co);
|
|
}
|
|
|
|
qemu_mutex_destroy(&pool_lock);
|
|
}
|
|
|
|
static void coroutine_swap(Coroutine *from, Coroutine *to)
|
|
{
|
|
CoroutineAction ret;
|
|
|
|
ret = qemu_coroutine_switch(from, to, COROUTINE_YIELD);
|
|
|
|
qemu_co_queue_run_restart(to);
|
|
|
|
switch (ret) {
|
|
case COROUTINE_YIELD:
|
|
return;
|
|
case COROUTINE_TERMINATE:
|
|
trace_qemu_coroutine_terminate(to);
|
|
coroutine_delete(to);
|
|
return;
|
|
default:
|
|
abort();
|
|
}
|
|
}
|
|
|
|
void qemu_coroutine_enter(Coroutine *co, void *opaque)
|
|
{
|
|
Coroutine *self = qemu_coroutine_self();
|
|
|
|
trace_qemu_coroutine_enter(self, co, opaque);
|
|
|
|
if (co->caller) {
|
|
fprintf(stderr, "Co-routine re-entered recursively\n");
|
|
abort();
|
|
}
|
|
|
|
co->caller = self;
|
|
co->entry_arg = opaque;
|
|
coroutine_swap(self, co);
|
|
}
|
|
|
|
void coroutine_fn qemu_coroutine_yield(void)
|
|
{
|
|
Coroutine *self = qemu_coroutine_self();
|
|
Coroutine *to = self->caller;
|
|
|
|
trace_qemu_coroutine_yield(self, to);
|
|
|
|
if (!to) {
|
|
fprintf(stderr, "Co-routine is yielding to no one\n");
|
|
abort();
|
|
}
|
|
|
|
self->caller = NULL;
|
|
coroutine_swap(self, to);
|
|
}
|