From: David Edmondson <dme@dme.org>
To: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org
Cc: kwolf@redhat.com, qemu-block@nongnu.org
Subject: Re: [PATCH 4/6] coroutine-lock: reimplement CoRwLock to fix downgrade bug
Date: Wed, 17 Mar 2021 17:47:07 +0000 [thread overview]
Message-ID: <m24kh9ekpw.fsf@dme.org> (raw)
In-Reply-To: <3146529c-788a-2d64-0369-cb6f28be2151@redhat.com>
On Wednesday, 2021-03-17 at 18:19:58 +01, Paolo Bonzini wrote:
> On 17/03/21 16:17, David Edmondson wrote:
>>> + if (tkt) {
>>> + if (tkt->read) {
>>> + if (lock->owners >= 0) {
>>> + lock->owners++;
>>> + co = tkt->co;
>>> + }
>>> + } else {
>>> + if (lock->owners == 0) {
>>> + lock->owners = -1;
>>> + co = tkt->co;
>>> + }
>>> + }
>>> + }
>>> +
>>> + if (co) {
>>> + QSIMPLEQ_REMOVE_HEAD(&lock->tickets, next);
>>> + qemu_co_mutex_unlock(&lock->mutex);
>>> + aio_co_wake(co);
>>> + } else {
>>> + qemu_co_mutex_unlock(&lock->mutex);
>>> + }
>>
>> This block could be pushed up into the earlier block, but I imagine that
>> the compiler will do it for you.
>
> I guess I could do
>
> if (!tkt || (tkt->read ? lock->owners < 0 : lock->owners != 0)) {
> qemu_co_mutex_unlock(&lock->mutex);
> return;
> }
> if (tkt->read) {
> lock->owners++;
> } else {
> lock->owners = -1;
> }
>
> co = tkt->co;
> QSIMPLEQ_REMOVE_HEAD(&lock->tickets, next);
> qemu_co_mutex_unlock(&lock->mutex);
> aio_co_wake(co);
>
> but I find it less readable.
Agreed.
> So that leaves only the of/or typo, right?
Yes.
dme.
--
In heaven there is no beer, that's why we drink it here.
next prev parent reply other threads:[~2021-03-17 17:49 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-17 12:16 [PATCH v4 0/6] coroutine rwlock downgrade fix, minor VDI changes Paolo Bonzini
2021-03-17 12:16 ` [PATCH 1/6] block/vdi: When writing new bmap entry fails, don't leak the buffer Paolo Bonzini
2021-03-17 12:16 ` [PATCH 2/6] block/vdi: Don't assume that blocks are larger than VdiHeader Paolo Bonzini
2021-03-17 12:16 ` [PATCH 3/6] coroutine/mutex: Store the coroutine in the CoWaitRecord only once Paolo Bonzini
2021-03-17 12:16 ` [PATCH 4/6] coroutine-lock: reimplement CoRwLock to fix downgrade bug Paolo Bonzini
2021-03-17 15:17 ` David Edmondson
2021-03-17 17:19 ` Paolo Bonzini
2021-03-17 17:47 ` David Edmondson [this message]
2021-03-17 12:16 ` [PATCH 5/6] test-coroutine: add rwlock upgrade test Paolo Bonzini
2021-03-17 15:19 ` David Edmondson
2021-03-17 12:16 ` [PATCH 6/6] test-coroutine: Add rwlock downgrade test Paolo Bonzini
2021-03-17 18:00 [PATCH v5 0/6] coroutine rwlock downgrade fix, minor VDI changes Paolo Bonzini
2021-03-17 18:00 ` [PATCH 4/6] coroutine-lock: reimplement CoRwlock to fix downgrade bug Paolo Bonzini
2021-03-24 16:15 ` Stefan Hajnoczi
2021-03-24 16:40 ` Paolo Bonzini
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