drm/udl: Fix inconsistent urbs.count value during udl_free_urb_list()

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In the current design, udl_get_urb() may be called asynchronously
during the driver freeing its URL list via udl_free_urb_list().
The problem is that the sync is determined by comparing the urbs.count
and urbs.available fields, while we clear urbs.count field only once
after udl_free_urb_list() finishes, i.e. during udl_free_urb_list(),
the state becomes inconsistent.

For fixing this inconsistency and also for hardening the locking
scheme, this patch does a slight refactoring of the code around
udl_get_urb() and udl_free_urb_list().  Now urbs.count is updated in
the same spinlock at extracting a URB from the list in
udl_free_url_list().

Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220908095115.23396-11-tiwai@suse.de

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This commit is contained in:

Takashi Iwai 2022-09-08 11:51:13 +02:00 • committed by Thomas Zimmermann

parent 046f4f0af7

commit c5c354a3a4

2 changed files with 30 additions and 20 deletions

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8

drivers/gpu/drm/udl/udl_drv.h

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42

drivers/gpu/drm/udl/udl_main.c

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