From: Fabiano Rosas <farosas@suse.de>
To: Peter Xu <peterx@redhat.com>, qemu-devel@nongnu.org
Cc: "Avihai Horon" <avihaih@nvidia.com>,
"Cédric Le Goater" <clg@redhat.com>,
peterx@redhat.com, "Alex Williamson" <alex.williamson@redhat.com>
Subject: Re: [PATCH v3 1/8] migration: Take migration object refcount earlier for threads
Date: Tue, 29 Oct 2024 15:48:05 -0300 [thread overview]
Message-ID: <875xpad9ui.fsf@suse.de> (raw)
In-Reply-To: <20241024213056.1395400-2-peterx@redhat.com>
Peter Xu <peterx@redhat.com> writes:
> Both migration thread or background snapshot thread will take a refcount of
> the migration object at the entrace of the thread function.
>
> That makes sense, because it protects the object from being freed by the
> main thread in migration_shutdown() later, but it might still race with it
> if the thread is scheduled too late. Consider the case right after
> pthread_create() happened, VM shuts down with the object released, but
> right after that the migration thread finally got created, referencing
> MigrationState* in the opaque pointer which is already freed.
>
> The only 100% safe way to make sure it won't get freed is taking the
> refcount right before the thread is created, meanwhile when BQL is held.
>
> Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
next prev parent reply other threads:[~2024-10-29 18:48 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-10-24 21:30 [PATCH v3 0/8] Migration: Make misc.h helpers available for whole VM lifecycle Peter Xu
2024-10-24 21:30 ` [PATCH v3 1/8] migration: Take migration object refcount earlier for threads Peter Xu
2024-10-25 8:36 ` Cédric Le Goater
2024-10-29 18:48 ` Fabiano Rosas [this message]
2024-10-24 21:30 ` [PATCH v3 2/8] migration: Unexport dirty_bitmap_mig_init() Peter Xu
2024-10-29 18:48 ` Fabiano Rosas
2024-10-24 21:30 ` [PATCH v3 3/8] migration: Unexport ram_mig_init() Peter Xu
2024-10-25 8:36 ` Cédric Le Goater
2024-10-29 18:49 ` Fabiano Rosas
2024-10-24 21:30 ` [PATCH v3 4/8] migration: Drop migration_is_setup_or_active() Peter Xu
2024-10-25 8:59 ` Cédric Le Goater
2024-10-29 19:04 ` Fabiano Rosas
2024-10-24 21:30 ` [PATCH v3 5/8] migration: Drop migration_is_idle() Peter Xu
2024-10-25 12:39 ` Cédric Le Goater
2024-10-29 19:07 ` Fabiano Rosas
2024-10-24 21:30 ` [PATCH v3 6/8] migration: Drop migration_is_device() Peter Xu
2024-10-24 21:30 ` [PATCH v3 7/8] migration: Unexport migration_is_active() Peter Xu
2024-10-28 7:43 ` Avihai Horon
2024-10-28 15:45 ` Peter Xu
2024-10-28 16:41 ` Avihai Horon
2024-10-28 16:58 ` Peter Xu
2024-10-28 17:20 ` Avihai Horon
2024-10-28 19:06 ` Peter Xu
2024-10-30 14:39 ` Avihai Horon
2024-10-30 14:43 ` Peter Xu
2024-10-24 21:30 ` [PATCH v3 8/8] migration: Protect updates to current_migration with a mutex Peter Xu
2024-10-25 12:50 ` Cédric Le Goater
2024-10-28 15:50 ` Peter Xu
2024-11-04 15:26 ` Cédric Le Goater
2024-10-29 20:22 ` [PATCH v3 0/8] Migration: Make misc.h helpers available for whole VM lifecycle Peter Xu
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