From: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
To: Eric Blake <eblake@redhat.com>
Cc: "Marc-André Lureau" <marcandre.lureau@gmail.com>,
qemu-devel@nongnu.org, "Hyman Huang" <yong.huang@smartx.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Gerd Hoffmann" <kraxel@redhat.com>,
qemu-block@nongnu.org, "Kevin Wolf" <kwolf@redhat.com>,
"Fabiano Rosas" <farosas@suse.de>,
"Mahmoud Mandour" <ma.mandourr@gmail.com>,
"John Snow" <jsnow@redhat.com>,
"Klaus Jensen" <its@irrelevant.dk>, "Fam Zheng" <fam@euphon.net>,
"Eugenio Pérez" <eperezma@redhat.com>,
"Bin Meng" <bin.meng@windriver.com>,
"Hanna Reitz" <hreitz@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
"Stefan Hajnoczi" <stefanha@redhat.com>,
"Philippe Mathieu-Daudé" <philmd@linaro.org>,
"Yuval Shaia" <yuval.shaia.ml@gmail.com>,
"Alex Bennée" <alex.bennee@linaro.org>,
"Jesper Devantier" <foss@defmacro.it>,
"Pierrick Bouvier" <pierrick.bouvier@linaro.org>,
"Keith Busch" <kbusch@kernel.org>,
"Marcel Apfelbaum" <marcel.apfelbaum@gmail.com>,
"Alexandre Iooss" <erdnaxe@crans.org>,
"Peter Xu" <peterx@redhat.com>
Subject: Re: [PATCH 06/19] block/stream: fix -Werror=maybe-uninitialized false-positives
Date: Tue, 2 Apr 2024 22:24:08 +0300 [thread overview]
Message-ID: <3064bc69-3d8e-4d7c-b640-a7ab703f9575@yandex-team.ru> (raw)
In-Reply-To: <mzls26xlctld3fd5fl3h5wdrbh6hb5i3xcakeslwzny5tva7ch@w6wnruxtefkl>
On 02.04.24 18:34, Eric Blake wrote:
> On Tue, Apr 02, 2024 at 12:58:43PM +0300, Vladimir Sementsov-Ogievskiy wrote:
>>>> Again, same false-positives, because of WITH_GRAPH_RDLOCK_GUARD()..
>>>>
>>>> Didn't you try to change WITH_ macros somehow, so that compiler believe in our good intentions?
>>>>
>>>
>>>
>>> #define WITH_QEMU_LOCK_GUARD_(x, var) \
>>> for (g_autoptr(QemuLockable) var = \
>>> qemu_lockable_auto_lock(QEMU_MAKE_LOCKABLE_NONNULL((x))); \
>>> var; \
>>> qemu_lockable_auto_unlock(var), var = NULL)
>>>
>>> I can't think of a clever way to rewrite this. The compiler probably
>>> thinks the loop may not run, due to the "var" condition. But how to
>>> convince it otherwise? it's hard to introduce another variable too..
>>
>>
>> hmm. maybe like this?
>>
>> #define WITH_QEMU_LOCK_GUARD_(x, var) \
>> for (g_autoptr(QemuLockable) var = \
>> qemu_lockable_auto_lock(QEMU_MAKE_LOCKABLE_NONNULL((x))), \
>> var2 = (void *)(true); \
>> var2; \
>> qemu_lockable_auto_unlock(var), var2 = NULL)
>>
>>
>> probably, it would be simpler for compiler to understand the logic this way. Could you check?
>
> Wouldn't that attach __attribute__((cleanup(xxx))) to var2, at which
> point we could cause the compiler to call xxx((void*)(true)) if the
> user does an early return inside the lock guard, with disastrous
> consequences? Or is the __attribute__ applied only to the first out
> of two declarations in a list?
>
Oh, most probably you are right, seems g_autoptr apply it to both variables. Also, we don't need qemu_lockable_auto_unlock(var) separate call, if we zero-out another variable. So, me fixing:
#define WITH_QEMU_LOCK_GUARD_(x, var) \
for (QemuLockable *var __attribute__((cleanup(qemu_lockable_auto_unlock))) = qemu_lockable_auto_lock(QEMU_MAKE_LOCKABLE_NONNULL((x))), \
*var2 = (void *)(true); \
var2; \
var2 = NULL)
(and we'll need to modify qemu_lockable_auto_unlock() to take "QemuLockable **x" argument)
--
Best regards,
Vladimir
next prev parent reply other threads:[~2024-04-02 19:25 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-28 10:20 [PATCH 00/19] -Werror=maybe-uninitialized fixes marcandre.lureau
2024-03-28 10:20 ` [PATCH 01/19] util/coroutine: fix -Werror=maybe-uninitialized false-positive marcandre.lureau
2024-04-02 20:17 ` Stefan Hajnoczi
2024-03-28 10:20 ` [PATCH 02/19] util/timer: with " marcandre.lureau
2024-03-28 10:20 ` [PATCH 03/19] hw/qxl: fix -Werror=maybe-uninitialized false-positives marcandre.lureau
2024-03-28 10:20 ` [PATCH 04/19] nbd: with -Werror=maybe-uninitialized false-positive marcandre.lureau
2024-03-28 14:30 ` Eric Blake
2024-03-28 10:20 ` [PATCH 05/19] block/mirror: fix " marcandre.lureau
2024-03-29 8:22 ` Vladimir Sementsov-Ogievskiy
2024-03-28 10:20 ` [PATCH 06/19] block/stream: fix -Werror=maybe-uninitialized false-positives marcandre.lureau
2024-03-29 8:34 ` Vladimir Sementsov-Ogievskiy
2024-04-02 9:12 ` Marc-André Lureau
2024-04-02 9:58 ` Vladimir Sementsov-Ogievskiy
2024-04-02 15:34 ` Eric Blake
2024-04-02 19:24 ` Vladimir Sementsov-Ogievskiy [this message]
2024-04-03 8:11 ` Marc-André Lureau
2024-04-03 8:31 ` Vladimir Sementsov-Ogievskiy
2024-04-03 9:24 ` Marc-André Lureau
2024-04-03 17:50 ` Eric Blake
2024-04-03 21:28 ` Vladimir Sementsov-Ogievskiy
2024-03-28 10:20 ` [PATCH 07/19] hw/ahci: fix -Werror=maybe-uninitialized false-positive marcandre.lureau
2024-03-28 10:20 ` [PATCH 08/19] hw/vhost-scsi: fix -Werror=maybe-uninitialized marcandre.lureau
2024-03-28 10:20 ` [PATCH 09/19] hw/sdhci: fix -Werror=maybe-uninitialized false-positive marcandre.lureau
2024-03-28 11:30 ` Philippe Mathieu-Daudé
2024-04-02 9:21 ` Marc-André Lureau
2024-03-28 10:20 ` [PATCH 10/19] hw/rdma: " marcandre.lureau
2024-03-28 10:20 ` [PATCH 11/19] migration/block: " marcandre.lureau
2024-03-28 19:40 ` Peter Xu
2024-03-28 10:20 ` [PATCH 12/19] migration: fix -Werror=maybe-uninitialized false-positives marcandre.lureau
2024-03-28 19:40 ` Peter Xu
2024-03-29 1:14 ` Yong Huang
2024-03-28 10:20 ` [PATCH 13/19] hw/virtio-blk: fix -Werror=maybe-uninitialized false-positive marcandre.lureau
2024-04-02 20:18 ` Stefan Hajnoczi
2024-03-28 10:20 ` [PATCH 14/19] plugins: " marcandre.lureau
2024-03-28 10:35 ` Pierrick Bouvier
2024-03-28 10:20 ` [PATCH 15/19] migration: " marcandre.lureau
2024-03-28 19:40 ` Peter Xu
2024-03-28 10:20 ` [PATCH 16/19] tests: fix -Werror=maybe-uninitialized marcandre.lureau
2024-03-28 10:20 ` [PATCH 17/19] hw/nvme: " marcandre.lureau
2024-04-02 10:40 ` Klaus Jensen
2024-03-28 10:20 ` [PATCH 18/19] hw/virtio: " marcandre.lureau
2024-03-28 10:20 ` [PATCH 19/19] RFC: hw/virtio: a potential leak fix marcandre.lureau
2024-03-28 14:31 ` [PATCH 00/19] -Werror=maybe-uninitialized fixes Eric Blake
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