From: Kevin Wolf <kwolf@redhat.com>
To: Markus Armbruster <armbru@redhat.com>
Cc: "Daniel P. Berrangé" <berrange@redhat.com>,
marcandre.lureau@gmail.com, qemu-devel@nongnu.org,
qemu-block@nongnu.org
Subject: Re: [PATCH] Simple & stupid coroutine-aware monitor_cur()
Date: Mon, 10 Aug 2020 14:19:14 +0200 [thread overview]
Message-ID: <20200810121914.GC14538@linux.fritz.box> (raw)
In-Reply-To: <87sgcyziul.fsf_-_@dusky.pond.sub.org>
Am 07.08.2020 um 15:27 hat Markus Armbruster geschrieben:
> This is just a sketch. It's incomplete, needs comments and a real
> commit message.
>
> Support for "[PATCH v6 09/12] hmp: Add support for coroutine command
> handlers" is missing. Marked FIXME.
>
> As is, it goes on top of Kevin's series. It is meant to be squashed
> into PATCH 06, except for the FIXME, which needs to be resolved in PATCH
> 09 instead.
>
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> ---
> monitor/monitor.c | 35 +++++++++++++++--------------------
> 1 file changed, 15 insertions(+), 20 deletions(-)
>
> diff --git a/monitor/monitor.c b/monitor/monitor.c
> index 50fb5b20d3..8601340285 100644
> --- a/monitor/monitor.c
> +++ b/monitor/monitor.c
> @@ -82,38 +82,34 @@ bool qmp_dispatcher_co_shutdown;
> */
> bool qmp_dispatcher_co_busy;
>
> -/*
> - * Protects mon_list, monitor_qapi_event_state, coroutine_mon,
> - * monitor_destroyed.
> - */
> +/* Protects mon_list, monitor_qapi_event_state, * monitor_destroyed. */
> QemuMutex monitor_lock;
> static GHashTable *monitor_qapi_event_state;
> -static GHashTable *coroutine_mon; /* Maps Coroutine* to Monitor* */
>
> MonitorList mon_list;
> int mon_refcount;
> static bool monitor_destroyed;
>
> +static Monitor **monitor_curp(Coroutine *co)
> +{
> + static __thread Monitor *thread_local_mon;
> + static Monitor *qmp_dispatcher_co_mon;
> +
> + if (qemu_coroutine_self() == qmp_dispatcher_co) {
> + return &qmp_dispatcher_co_mon;
> + }
> + /* FIXME the coroutine hidden in handle_hmp_command() */
> + return &thread_local_mon;
> +}
Is thread_local_mon supposed to ever be set? The only callers of
monitor_set_cur() are the HMP and QMP dispatchers, which will return
something different.
So should we return NULL insetad of thread_local_mon...
> Monitor *monitor_cur(void)
> {
> - Monitor *mon;
> -
> - qemu_mutex_lock(&monitor_lock);
> - mon = g_hash_table_lookup(coroutine_mon, qemu_coroutine_self());
> - qemu_mutex_unlock(&monitor_lock);
> -
> - return mon;
> + return *monitor_curp(qemu_coroutine_self());
> }
...and return NULL here if monitor_curp() returned NULL...
> void monitor_set_cur(Coroutine *co, Monitor *mon)
> {
> - qemu_mutex_lock(&monitor_lock);
> - if (mon) {
> - g_hash_table_replace(coroutine_mon, co, mon);
> - } else {
> - g_hash_table_remove(coroutine_mon, co);
> - }
> - qemu_mutex_unlock(&monitor_lock);
> + *monitor_curp(co) = mon;
...and assert(monitor_curp(co) != NULL) here?
This approach looks workable, though the implementation of
monitor_curp() feels a bit brittle. The code is not significantly
simpler than the hash table based approach, but the assumptions it makes
are a bit more hidden.
Saving the locks is more a theoretical improvement because all callers
are slows paths anyway.
Kevin
next prev parent reply other threads:[~2020-08-10 12:20 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-28 15:37 [PATCH v6 00/12] monitor: Optionally run handlers in coroutines Kevin Wolf
2020-05-28 15:37 ` [PATCH v6 01/12] monitor: Add Monitor parameter to monitor_set_cpu() Kevin Wolf
2020-05-28 18:24 ` Eric Blake
2020-08-04 11:19 ` Markus Armbruster
2020-05-28 15:37 ` [PATCH v6 02/12] monitor: Use getter/setter functions for cur_mon Kevin Wolf
2020-05-28 18:31 ` Eric Blake
2020-06-02 13:36 ` Kevin Wolf
2020-05-28 18:36 ` Eric Blake
2020-08-04 12:46 ` Markus Armbruster
2020-08-04 16:16 ` Kevin Wolf
2020-08-05 7:19 ` Markus Armbruster
2020-08-05 8:25 ` Kevin Wolf
2020-08-05 4:45 ` Markus Armbruster
2020-05-28 15:37 ` [PATCH v6 03/12] hmp: Set cur_mon only in handle_hmp_command() Kevin Wolf
2020-05-28 18:37 ` Eric Blake
2020-08-04 12:54 ` Markus Armbruster
2020-05-28 15:37 ` [PATCH v6 04/12] qmp: Assert that no other monitor is active Kevin Wolf
2020-05-28 18:38 ` Eric Blake
2020-08-04 12:57 ` Markus Armbruster
2020-05-28 15:37 ` [PATCH v6 05/12] qmp: Call monitor_set_cur() only in qmp_dispatch() Kevin Wolf
2020-05-28 18:42 ` Eric Blake
2020-08-04 13:17 ` Markus Armbruster
2020-05-28 15:37 ` [PATCH v6 06/12] monitor: Make current monitor a per-coroutine property Kevin Wolf
2020-05-28 18:44 ` Eric Blake
2020-08-04 13:50 ` Markus Armbruster
2020-08-04 16:06 ` Kevin Wolf
2020-08-05 7:28 ` Markus Armbruster
2020-08-05 8:32 ` Kevin Wolf
2020-08-07 13:09 ` Ways to do per-coroutine properties (was: [PATCH v6 06/12] monitor: Make current monitor a per-coroutine property) Markus Armbruster
2020-08-07 13:27 ` [PATCH] Simple & stupid coroutine-aware monitor_cur() Markus Armbruster
2020-08-10 12:19 ` Kevin Wolf [this message]
2020-08-26 12:37 ` Markus Armbruster
2020-08-07 13:29 ` [PATCH] Coroutine-aware monitor_cur() with coroutine-specific data Markus Armbruster
2020-08-10 12:58 ` Kevin Wolf
2020-08-26 12:40 ` Markus Armbruster
2020-08-26 13:49 ` Kevin Wolf
2020-08-04 16:14 ` [PATCH v6 06/12] monitor: Make current monitor a per-coroutine property Daniel P. Berrangé
2020-05-28 15:37 ` [PATCH v6 07/12] qapi: Add a 'coroutine' flag for commands Kevin Wolf
2020-05-28 15:37 ` [PATCH v6 08/12] qmp: Move dispatcher to a coroutine Kevin Wolf
2020-08-05 10:03 ` Markus Armbruster
2020-05-28 15:37 ` [PATCH v6 09/12] hmp: Add support for coroutine command handlers Kevin Wolf
2020-08-05 10:33 ` Markus Armbruster
2020-05-28 15:37 ` [PATCH v6 10/12] util/async: Add aio_co_reschedule_self() Kevin Wolf
2020-05-28 15:37 ` [PATCH v6 11/12] block: Add bdrv_co_move_to_aio_context() Kevin Wolf
2020-05-28 15:37 ` [PATCH v6 12/12] block: Convert 'block_resize' to coroutine Kevin Wolf
2020-08-04 11:16 ` [PATCH v6 00/12] monitor: Optionally run handlers in coroutines Markus Armbruster
2020-08-05 11:34 ` Markus Armbruster
2020-09-03 10:49 ` Markus Armbruster
2020-09-03 12:45 ` Kevin Wolf
2020-09-03 14:17 ` Markus Armbruster
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