From: Stefan Hajnoczi <stefanha@redhat.com>
To: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>,
Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>,
qemu-block@nongnu.org, qemu-devel@nongnu.org,
Max Reitz <mreitz@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>, John Snow <jsnow@redhat.com>
Subject: Re: [PATCH 5/6] co-shared-resource: protect with a mutex
Date: Wed, 12 May 2021 16:44:59 +0100 [thread overview]
Message-ID: <YJv3+y42z0Ld1nY0@stefanha-x1.localdomain> (raw)
In-Reply-To: <20210510085941.22769-6-eesposit@redhat.com>
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On Mon, May 10, 2021 at 10:59:40AM +0200, Emanuele Giuseppe Esposito wrote:
> co-shared-resource is currently not thread-safe, as also reported
> in co-shared-resource.h. Add a QemuMutex because co_try_get_from_shres
> can also be invoked from non-coroutine context.
>
> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
> ---
> util/qemu-co-shared-resource.c | 26 ++++++++++++++++++++++----
> 1 file changed, 22 insertions(+), 4 deletions(-)
Hmm...this thread-safety change is more fine-grained than I was
expecting. If we follow this strategy basically any data structure used
by coroutines needs its own fine-grained lock (like Java's Object base
class which has its own lock).
I'm not sure I like it since callers may still need coarser grained
locks to protect their own state or synchronize access to multiple
items of data. Also, some callers may not need thread-safety.
Can the caller to be responsible for locking instead (e.g. using
CoMutex)?
> diff --git a/util/qemu-co-shared-resource.c b/util/qemu-co-shared-resource.c
> index 1c83cd9d29..c455d02a1e 100644
> --- a/util/qemu-co-shared-resource.c
> +++ b/util/qemu-co-shared-resource.c
> @@ -32,6 +32,7 @@ struct SharedResource {
> uint64_t available;
>
> CoQueue queue;
> + QemuMutex lock;
Please add a comment indicating what this lock protects.
Thread safety should also be documented in the header file so API users
know what to expect.
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next prev parent reply other threads:[~2021-05-12 15:48 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-10 8:59 [PATCH 0/6] block-copy: make helper APIs thread safe Emanuele Giuseppe Esposito
2021-05-10 8:59 ` [PATCH 1/6] ratelimit: treat zero speed as unlimited Emanuele Giuseppe Esposito
2021-05-10 11:00 ` Vladimir Sementsov-Ogievskiy
2021-05-10 8:59 ` [PATCH 2/6] block-copy: let ratelimit handle a speed of 0 Emanuele Giuseppe Esposito
2021-05-10 11:06 ` Vladimir Sementsov-Ogievskiy
2021-05-10 8:59 ` [PATCH 3/6] blockjob: " Emanuele Giuseppe Esposito
2021-05-10 11:17 ` Vladimir Sementsov-Ogievskiy
2021-05-10 8:59 ` [PATCH 4/6] progressmeter: protect with a mutex Emanuele Giuseppe Esposito
2021-05-10 11:28 ` Vladimir Sementsov-Ogievskiy
2021-05-10 16:52 ` Emanuele Giuseppe Esposito
2021-05-10 17:17 ` Vladimir Sementsov-Ogievskiy
2021-05-10 17:57 ` Emanuele Giuseppe Esposito
2021-05-11 12:28 ` Paolo Bonzini
2021-05-12 7:09 ` Vladimir Sementsov-Ogievskiy
2021-05-12 15:53 ` Stefan Hajnoczi
2021-05-10 8:59 ` [PATCH 5/6] co-shared-resource: " Emanuele Giuseppe Esposito
2021-05-10 11:40 ` Vladimir Sementsov-Ogievskiy
2021-05-11 8:34 ` Paolo Bonzini
2021-05-12 15:44 ` Stefan Hajnoczi [this message]
2021-05-12 18:30 ` Paolo Bonzini
2021-05-14 14:10 ` Emanuele Giuseppe Esposito
2021-05-14 14:26 ` Vladimir Sementsov-Ogievskiy via
2021-05-14 14:32 ` Emanuele Giuseppe Esposito
2021-05-14 15:30 ` Vladimir Sementsov-Ogievskiy via
2021-05-14 17:28 ` Emanuele Giuseppe Esposito
2021-05-14 21:15 ` Vladimir Sementsov-Ogievskiy via
2021-05-14 21:53 ` Emanuele Giuseppe Esposito
2021-05-15 7:11 ` Vladimir Sementsov-Ogievskiy via
2021-05-14 17:55 ` Paolo Bonzini
2021-05-10 8:59 ` [PATCH 6/6] aiopool: " Emanuele Giuseppe Esposito
2021-05-10 11:56 ` Vladimir Sementsov-Ogievskiy
2021-05-11 8:34 ` Paolo Bonzini
2021-05-12 15:19 ` Stefan Hajnoczi
2021-05-10 10:55 ` [PATCH 0/6] block-copy: make helper APIs thread safe Vladimir Sementsov-Ogievskiy
2021-05-12 14:24 ` Stefan Hajnoczi
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