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mesa: Fix locking of GLsync objects.

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GLsync objects had a race condition when used from multiple threads
(which is the main point of the extension, really); it could be
validated as a sync object at the beginning of the function, and then
deleted by another thread before use, causing crashes. Fix this by
changing all casts from GLsync to struct gl_sync_object to a new
function _mesa_get_and_ref_sync() that validates and increases
the refcount.

In a similar vein, validation itself uses _mesa_set_search(), which
requires synchronization -- it was called without a mutex held, causing
spurious error returns and other issues. Since _mesa_get_and_ref_sync()
now takes the shared context mutex, this problem is also resolved.

Fixes bug #92757, found while developing Nageru, my live video mixer
(due for release at FOSDEM 2016).

v2: Marek: silence warnings, fix declaration after code

Signed-off-by: Steinar H. Gunderson <sesse@google.com>
Cc: "11.0 11.1" <mesa-stable@lists.freedesktop.org>
Signed-off-by: Marek Olšák <marek.olsak@amd.com>
This commit is contained in:
Steinar H. Gunderson
2016-02-02 01:16:51 +01:00
committed by Marek Olšák
parent 156e81f305
commit feb53912f8
4 changed files with 66 additions and 49 deletions
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src/mesa/main/shared.c
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@@ -338,7 +338,7 @@ free_shared_state(struct gl_context *ctx, struct gl_shared_state *shared)
struct set_entry *entry;
set_foreach(shared->SyncObjects, entry) {
_mesa_unref_sync_object(ctx, (struct gl_sync_object *) entry->key);
_mesa_unref_sync_object(ctx, (struct gl_sync_object *) entry->key, 1);
}
}
_mesa_set_destroy(shared->SyncObjects, NULL);