On 3/8/23 10:08, Paolo Bonzini wrote:
On 3/8/23 17:47, Richard Henderson wrote:
The case that I was imagining for smp_mb__before_rmw() is something like this:
wake_me = true;
smp_mb__before_rmw();
if (qatomic_xchg(&can_sleep, true)) { ... }
where you really need a full barrier.
On 3/8/23 17:47, Richard Henderson wrote:
The case that I was imagining for smp_mb__before_rmw() is something
like this:
wake_me = true;
smp_mb__before_rmw();
if (qatomic_xchg(&can_sleep, true)) { ... }
where you really need a full barrier.
What is different about this that do
On 3/8/23 02:49, Paolo Bonzini wrote:
On 3/7/23 18:26, Richard Henderson wrote:
On 3/7/23 09:00, Paolo Bonzini wrote:
while QSLIST_REMOVE_HEAD in the dequeuing thread is not ordered at all:
y.store(0, mo_relaxed); // QSLIST_REMOVE_HEAD
x.store(0, mo_release);
On 3/7/23 18:26, Richard Henderson wrote:
On 3/7/23 09:00, Paolo Bonzini wrote:
while QSLIST_REMOVE_HEAD in the dequeuing thread is not ordered at all:
y.store(0, mo_relaxed); // QSLIST_REMOVE_HEAD
x.store(0, mo_release); // fetch_and
As I read aio_bh_queu
On 3/7/23 09:00, Paolo Bonzini wrote:
while QSLIST_REMOVE_HEAD in the dequeuing thread is not ordered at all:
y.store(0, mo_relaxed); // QSLIST_REMOVE_HEAD
x.store(0, mo_release); // fetch_and
As I read aio_bh_queue, this is exactly the situation you descri
On 3/7/23 16:54, Richard Henderson wrote:
Just to be safe, I tried modeling this with cppmem
(http://svr-pes20-cppmem.cl.cam.ac.uk/cppmem/); support for
compare-and-swap is very limited, therefore the test looks nothing
like the C code(*), but it should be ok:
You do realize that QSLIST_REM
On 3/7/23 02:49, Paolo Bonzini wrote:
On 3/7/23 00:39, Richard Henderson wrote:
On 3/6/23 14:33, Paolo Bonzini wrote:
@@ -107,11 +114,8 @@ static QEMUBH *aio_bh_dequeue(BHList *head, unsigned
*flags)
QSLIST_REMOVE_HEAD(head, next);
/*
- * The qatomic_and is paired with aio_bh_e
On 3/7/23 00:39, Richard Henderson wrote:
On 3/6/23 14:33, Paolo Bonzini wrote:
@@ -107,11 +114,8 @@ static QEMUBH *aio_bh_dequeue(BHList *head,
unsigned *flags)
QSLIST_REMOVE_HEAD(head, next);
/*
- * The qatomic_and is paired with aio_bh_enqueue(). The implicit
memory
- *
On 3/6/23 14:33, Paolo Bonzini wrote:
@@ -107,11 +114,8 @@ static QEMUBH *aio_bh_dequeue(BHList *head, unsigned
*flags)
QSLIST_REMOVE_HEAD(head, next);
/*
- * The qatomic_and is paired with aio_bh_enqueue(). The implicit memory
- * barrier ensures that the callback sees
Reviewed-by: Stefan Hajnoczi
Ever since commit 8c6b0356b539 ("util/async: make bh_aio_poll() O(1)",
2020-02-22), synchronization between qemu_bh_schedule() and aio_bh_poll()
is happening when the bottom half is enqueued in the bh_list; not
when the flags are set. Update the documentation to match.
Signed-off-by: Paolo Bonzin
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