From: Eric Blake <eblake@redhat.com>
To: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Cc: kwolf@redhat.com, qemu-block@nongnu.org, qemu-devel@nongnu.org,
mreitz@redhat.com, Stefan Hajnoczi <stefanha@redhat.com>,
pbonzini@redhat.com
Subject: Re: [PATCH v4 01/32] co-queue: drop extra coroutine_fn marks
Date: Thu, 10 Jun 2021 12:22:04 -0500 [thread overview]
Message-ID: <20210610172204.w2gtdeoj3v72m5rg@redhat.com> (raw)
In-Reply-To: <20210610100802.5888-2-vsementsov@virtuozzo.com>
On Thu, Jun 10, 2021 at 01:07:31PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> qemu_co_queue_next() and qemu_co_queue_restart_all() just call
> aio_co_wake() which works well in non-coroutine context. So these
> functions can be called from non-coroutine context as well. And
> actually qemu_co_queue_restart_all() is called from
> nbd_cancel_in_flight(), which is called from non-coroutine context.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
> include/qemu/coroutine.h | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
In the back of my mind, I have to repeatedly question my faulty memory
on whether:
absence of coroutine_fn means this function is unsafe to call from a
coroutine context (that is, coroutines can only call functions tagged
with coroutine_fn)
vs.
presence of coroutine_fn means this function must only use
coroutine-safe actions, but not all coroutine-safe functions have this
tag (in particular, functions which are designed to work both in or
out of coroutine context do not have the tag, but coroutines can call
functions without the tag)
But thankfully, rereading include/qemu/coroutine.h clears it up and
both of my initial thoughts are wrong although the second is closer;
it is yet another definition:
presence of coroutine_fn means this function must NOT be called except
from a coroutine context. coroutines can call functions with or
without the tag, but if they lack the tag, the coroutine must ensure
the function won't block.
Thus, adding the tag is something we do when writing a function that
obeys coroutine rules and requires a coroutine context to already be
present, and once a function is then relaxed enough to work from both
regular and coroutine functions, we drop the marker. But we keep the
_co_ in the function name to remind ourselves that it is
coroutine-safe, in addition to normal-safe.
And your patch is doing just that - we have functions that work from
both normal and coroutine context, so we can drop the marker but keep
_co_ in the name.
Reviewed-by: Eric Blake <eblake@redhat.com>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3266
Virtualization: qemu.org | libvirt.org
next prev parent reply other threads:[~2021-06-10 17:23 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-10 10:07 [PATCH v4 00/32] block/nbd: rework client connection Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 01/32] co-queue: drop extra coroutine_fn marks Vladimir Sementsov-Ogievskiy
2021-06-10 17:22 ` Eric Blake [this message]
2021-06-10 17:37 ` Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 02/32] block/nbd: fix channel object leak Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 03/32] block/nbd: fix how state is cleared on nbd_open() failure paths Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 04/32] block/nbd: connect_thread_func(): do qio_channel_set_delay(false) Vladimir Sementsov-Ogievskiy
2021-06-10 18:37 ` Eric Blake
2021-06-10 10:07 ` [PATCH v4 05/32] qemu-sockets: introduce socket_address_parse_named_fd() Vladimir Sementsov-Ogievskiy
2021-06-11 13:22 ` Eric Blake
2021-06-11 14:10 ` Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 06/32] block/nbd: call socket_address_parse_named_fd() in advance Vladimir Sementsov-Ogievskiy
2021-06-11 13:54 ` Eric Blake
2021-06-10 10:07 ` [PATCH v4 07/32] block/nbd: ensure ->connection_thread is always valid Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 08/32] block/nbd: nbd_client_handshake(): fix leak of s->ioc Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 09/32] block/nbd: BDRVNBDState: drop unused connect_err and connect_status Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 10/32] block/nbd: simplify waking of nbd_co_establish_connection() Vladimir Sementsov-Ogievskiy
2021-06-11 14:06 ` Eric Blake
2021-06-10 10:07 ` [PATCH v4 11/32] block/nbd: drop thr->state Vladimir Sementsov-Ogievskiy
2021-06-11 14:25 ` Eric Blake
2021-06-10 10:07 ` [PATCH v4 12/32] block/nbd: bs-independent interface for nbd_co_establish_connection() Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 13/32] block/nbd: make nbd_co_establish_connection_cancel() bs-independent Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 14/32] block/nbd: rename NBDConnectThread to NBDClientConnection Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 15/32] block/nbd: introduce nbd_client_connection_new() Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 16/32] block/nbd: introduce nbd_client_connection_release() Vladimir Sementsov-Ogievskiy
2021-06-11 14:28 ` Eric Blake
2021-06-10 10:07 ` [PATCH v4 17/32] nbd: move connection code from block/nbd to nbd/client-connection Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 18/32] nbd/client-connection: use QEMU_LOCK_GUARD Vladimir Sementsov-Ogievskiy
2021-06-11 14:31 ` Eric Blake
2021-06-10 10:07 ` [PATCH v4 19/32] nbd/client-connection: add possibility of negotiation Vladimir Sementsov-Ogievskiy
2021-06-11 15:07 ` Eric Blake
2021-06-10 10:07 ` [PATCH v4 20/32] nbd/client-connection: implement connection retry Vladimir Sementsov-Ogievskiy
2021-06-11 15:12 ` Eric Blake
2021-11-22 16:30 ` Eric Blake
2021-11-22 17:17 ` Vladimir Sementsov-Ogievskiy
2021-11-22 21:51 ` Eric Blake
2021-06-10 10:07 ` [PATCH v4 21/32] nbd/client-connection: shutdown connection on release Vladimir Sementsov-Ogievskiy
2021-06-11 15:27 ` Eric Blake
2021-06-10 10:07 ` [PATCH v4 22/32] block/nbd: split nbd_handle_updated_info out of nbd_client_handshake() Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 23/32] block/nbd: use negotiation of NBDClientConnection Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 24/32] block/nbd: don't touch s->sioc in nbd_teardown_connection() Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 25/32] block/nbd: drop BDRVNBDState::sioc Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 26/32] nbd/client-connection: return only one io channel Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 27/32] block-coroutine-wrapper: allow non bdrv_ prefix Vladimir Sementsov-Ogievskiy
2021-06-10 10:07 ` [PATCH v4 28/32] block/nbd: split nbd_co_do_establish_connection out of nbd_reconnect_attempt Vladimir Sementsov-Ogievskiy
2021-06-11 15:29 ` Eric Blake
2021-06-10 10:07 ` [PATCH v4 29/32] nbd/client-connection: add option for non-blocking connection attempt Vladimir Sementsov-Ogievskiy
2021-06-10 10:08 ` [PATCH v4 30/32] block/nbd: reuse nbd_co_do_establish_connection() in nbd_open() Vladimir Sementsov-Ogievskiy
2021-06-10 10:08 ` [PATCH v4 31/32] block/nbd: add nbd_client_connected() helper Vladimir Sementsov-Ogievskiy
2021-06-10 10:08 ` [PATCH v4 32/32] block/nbd: safer transition to receiving request Vladimir Sementsov-Ogievskiy
2021-06-11 15:55 ` [PATCH v4 00/32] block/nbd: rework client connection Eric Blake
2021-06-11 17:23 ` Vladimir Sementsov-Ogievskiy
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