Commit 1b7f01d9 authored by Kevin Wolf's avatar Kevin Wolf
Browse files

coroutine: Assert that no locks are held on termination 



A coroutine that takes a lock must also release it again. If the
coroutine terminates without having released all its locks, it's buggy
and we'll probably run into a deadlock sooner or later. Make sure that
we don't get such cases.

Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
Reviewed-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Reviewed-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent 0e438cdc

include/qemu/coroutine_int.h

+1 −0
Original line number Diff line number Diff line
@@ -39,6 +39,7 @@ struct Coroutine { 
    void *entry_arg;

    Coroutine *caller;

    QSLIST_ENTRY(Coroutine) pool_next;

    size_t locks_held;



    /* Coroutines that should be woken up when we yield or terminate */

    QSIMPLEQ_HEAD(, Coroutine) co_queue_wakeup;

util/qemu-coroutine-lock.c

+11 −0
Original line number Diff line number Diff line
@@ -130,6 +130,7 @@ void coroutine_fn qemu_co_mutex_lock(CoMutex *mutex) 


    mutex->locked = true;

    mutex->holder = self;

    self->locks_held++;



    trace_qemu_co_mutex_lock_return(mutex, self);

}
@@ -146,6 +147,7 @@ void coroutine_fn qemu_co_mutex_unlock(CoMutex *mutex) 


    mutex->locked = false;

    mutex->holder = NULL;

    self->locks_held--;

    qemu_co_queue_next(&mutex->queue);



    trace_qemu_co_mutex_unlock_return(mutex, self);
@@ -159,14 +161,19 @@ void qemu_co_rwlock_init(CoRwlock *lock) 


void qemu_co_rwlock_rdlock(CoRwlock *lock)

{

    Coroutine *self = qemu_coroutine_self();



    while (lock->writer) {

        qemu_co_queue_wait(&lock->queue);

    }

    lock->reader++;

    self->locks_held++;

}



void qemu_co_rwlock_unlock(CoRwlock *lock)

{

    Coroutine *self = qemu_coroutine_self();



    assert(qemu_in_coroutine());

    if (lock->writer) {

        lock->writer = false;
@@ -179,12 +186,16 @@ void qemu_co_rwlock_unlock(CoRwlock *lock) 
            qemu_co_queue_next(&lock->queue);

        }

    }

    self->locks_held--;

}



void qemu_co_rwlock_wrlock(CoRwlock *lock)

{

    Coroutine *self = qemu_coroutine_self();



    while (lock->writer || lock->reader) {

        qemu_co_queue_wait(&lock->queue);

    }

    lock->writer = true;

    self->locks_held++;

}

util/qemu-coroutine.c

+1 −0
Original line number Diff line number Diff line
@@ -122,6 +122,7 @@ void qemu_coroutine_enter(Coroutine *co) 
    case COROUTINE_YIELD:

        return;

    case COROUTINE_TERMINATE:

        assert(!co->locks_held);

        trace_qemu_coroutine_terminate(co);

        coroutine_delete(co);

        return;