]> pilppa.com Git - linux-2.6-omap-h63xx.git/commit
ps3fb: fix deadlock on kexec()
authorJeremy Kerr <jk@ozlabs.org>
Fri, 11 Jan 2008 13:28:04 +0000 (14:28 +0100)
committerLinus Torvalds <torvalds@woody.linux-foundation.org>
Fri, 11 Jan 2008 19:47:43 +0000 (11:47 -0800)
commit8dab63761219d7bc6a7d7d3b5f0fca76af5533a5
tree3354b2867c05507acb5618f961cdf982f98e2b41
parentba21611c9c0031ca8388cae5e43b38c29c8b595d
ps3fb: fix deadlock on kexec()

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>
drivers/video/ps3fb.c