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From: Emanuele Giuseppe Esposito <eesposit@redhat.com>
To: qemu-block@nongnu.org
Cc: "Kevin Wolf" <kwolf@redhat.com>, "Fam Zheng" <fam@euphon.net>,
	"Vladimir Sementsov-Ogievskiy" <vsementsov@virtuozzo.com>,
	"Daniel P. Berrangé" <berrange@redhat.com>,
	"Eduardo Habkost" <ehabkost@redhat.com>,
	"Juan Quintela" <quintela@redhat.com>,
	"John Snow" <jsnow@redhat.com>,
	"Emanuele Giuseppe Esposito" <eesposit@redhat.com>,
	"Richard Henderson" <richard.henderson@linaro.org>,
	"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
	qemu-devel@nongnu.org, "Hanna Reitz" <hreitz@redhat.com>,
	"Stefan Hajnoczi" <stefanha@redhat.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Eric Blake" <eblake@redhat.com>
Subject: [RFC PATCH 1/4] main-loop.h: introduce qemu_in_main_thread()
Date: Wed,  8 Sep 2021 09:10:18 -0400	[thread overview]
Message-ID: <20210908131021.774533-2-eesposit@redhat.com> (raw)
In-Reply-To: <20210908131021.774533-1-eesposit@redhat.com>

When invoked from the main loop, this function is the same
as qemu_mutex_iothread_locked, and returns true if the BQL is held.
When invoked from iothreads or tests, it returns true only
if the current AioContext is the Main Loop.

This essentially just extends qemu_mutex_iothread_locked to work
also in unit tests or other users like storage-daemon, that run
in the Main Loop but end up using the implementation in
stubs/iothread-lock.c.

Using qemu_mutex_iothread_locked in unit tests defaults to false
because they use the implementation in stubs/iothread-lock,
making all assertions added in next patches fail despite the
AioContext is still the main loop.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
 include/qemu/main-loop.h | 13 +++++++++++++
 softmmu/cpus.c           |  5 +++++
 stubs/iothread-lock.c    |  5 +++++
 3 files changed, 23 insertions(+)

diff --git a/include/qemu/main-loop.h b/include/qemu/main-loop.h
index 8dbc6fcb89..c6547207f7 100644
--- a/include/qemu/main-loop.h
+++ b/include/qemu/main-loop.h
@@ -245,6 +245,19 @@ AioContext *iohandler_get_aio_context(void);
  */
 bool qemu_mutex_iothread_locked(void);
 
+/**
+ * qemu_in_main_thread: Return true if the function runs with BQL
+ * or in the main loop AioContext.
+ *
+ * This function falls back to qemu_mutex_iothread_locked() if
+ * called from the main loop, otherwise it checks if the current
+ * AioContext is the main loop. This is useful to check that the BQL
+ * is held, and not make it return false when invoked by unit
+ * tests or other users like storage-daemon that end up using
+ * stubs/iothread-lock.c implementation.
+ */
+bool qemu_in_main_thread(void);
+
 /**
  * qemu_mutex_lock_iothread: Lock the main loop mutex.
  *
diff --git a/softmmu/cpus.c b/softmmu/cpus.c
index 071085f840..3f61a3c31d 100644
--- a/softmmu/cpus.c
+++ b/softmmu/cpus.c
@@ -481,6 +481,11 @@ bool qemu_mutex_iothread_locked(void)
     return iothread_locked;
 }
 
+bool qemu_in_main_thread(void)
+{
+    return qemu_mutex_iothread_locked();
+}
+
 /*
  * The BQL is taken from so many places that it is worth profiling the
  * callers directly, instead of funneling them all through a single function.
diff --git a/stubs/iothread-lock.c b/stubs/iothread-lock.c
index 5b45b7fc8b..ff7386e42c 100644
--- a/stubs/iothread-lock.c
+++ b/stubs/iothread-lock.c
@@ -6,6 +6,11 @@ bool qemu_mutex_iothread_locked(void)
     return false;
 }
 
+bool qemu_in_main_thread(void)
+{
+    return qemu_get_current_aio_context() == qemu_get_aio_context();
+}
+
 void qemu_mutex_lock_iothread_impl(const char *file, int line)
 {
 }
-- 
2.27.0



  reply	other threads:[~2021-09-08 13:13 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-08 13:10 [RFC PATCH 0/4] block layer: split block APIs in graph and I/O Emanuele Giuseppe Esposito
2021-09-08 13:10 ` Emanuele Giuseppe Esposito [this message]
2021-09-13 13:15   ` [RFC PATCH 1/4] main-loop.h: introduce qemu_in_main_thread() Stefan Hajnoczi
2021-09-08 13:10 ` [RFC PATCH 2/4] migration: block-dirty-bitmap: add missing qemu_mutex_lock_iothread Emanuele Giuseppe Esposito
2021-09-13 13:19   ` Stefan Hajnoczi
2021-09-08 13:10 ` [RFC PATCH 3/4] include/sysemu/block-backend: split header into I/O and graph API Emanuele Giuseppe Esposito
2021-09-13 13:27   ` Stefan Hajnoczi
2021-09-15 12:14     ` Paolo Bonzini
2021-09-15 14:38       ` Stefan Hajnoczi
2021-09-13 13:41   ` Stefan Hajnoczi
2021-09-08 13:10 ` [RFC PATCH 4/4] block/block-backend.c: assertions for block-backend Emanuele Giuseppe Esposito
2021-09-13 13:38   ` Stefan Hajnoczi
2021-09-13 13:10 ` [RFC PATCH 0/4] block layer: split block APIs in graph and I/O Stefan Hajnoczi
2021-09-15 12:11   ` Paolo Bonzini
2021-09-15 14:43     ` Stefan Hajnoczi
2021-09-16 14:03       ` Emanuele Giuseppe Esposito
2021-09-16 19:49         ` Paolo Bonzini
2021-09-13 13:39 ` Stefan Hajnoczi

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