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Since the introduction of the acquire_console_sem calls in
0333d83509c7d8496c8965b5ba9bc0c98e83c259, kexecing can cause the
kernel to deadlock:
ps3fb_shutdown()
-> unregister_framebuffer()
-> fb_notifier_call_chain(FB_EVENT_FB_UNBIND)
-> fbcon_fb_unbind()
-> unbind_con_driver()
-> bind_con_driver()
[ acquires console_sem ]
-> fbcon_deinit()
-> fbops->fb_release(newinfo, 0)
-> ps3fb_release()
-> ps3fb_sync()
[ acquires console_sem ]
This change avoids the deadlock by moving the acquire_console_sem()
out of ps3fb_sync(), and puts it into the two other callsites, leaving
ps3fb_release() to call ps3fb_sync() without the console semaphore.
[Geert]
- Corrected call sequence above
- ps3fb_release() may be called with and without console_sem held. This is an
inconsistency that should be fixed at the fb level, but for now, try to
acquire console_sem in ps3fb_release().
I think it's safer to let ps3fb_release() try to acquire console_sem and
not refresh the screen if it fails, than to call ps3fb_sync() without
holding console_sem, as ps3fb_par may be modified at the same time, causing
crashes or lockups.
Besides, ps3fb_release() only calls ps3fb_sync() to refresh the screen
when display flipping is disabled, which is an uncommon case (except during
shutdown/kexec).
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
8dab637612