On 3 January 2013 21:11, Alan Cox [off-list ref] wrote:
On Thu, 3 Jan 2013 20:56:30 +0800
Daniel J Blueman [off-list ref] wrote:
quoted
On 3.8-rc2 with lockdep enabled and dual-GPU setup (Macbook Pro
Retina), I see two releated lock inversion issues with the EFI
framebuffer, leading to possible deadlock: when X takes over from the
EFI framebuffer [1] and when nouveau releases the framebuffer when
being vgaswitcherood [2].
Let me know if you'd like any testing or analysis when I can get the time.
The fb layer locking was broken. I posted patches early December which
should have fixed the ones we know about. ('fb: Rework locking to fix
lock ordering on takeover').
Superb work, Alan!
The only patch I could find [1] (mid Nov) looks like it needs another
sites updating, since we now see an i915 vs efifb lock ordering issue
[2].
I can get some time next week to take a look if it helps.
Thanks,
Daniel
--- [1] https://patchwork.kernel.org/patch/1757061/
--- [2]
[drm] Memory usable by graphics device = 2048M
checking generic (b0000000 1440000) vs hw (b0000000 10000000)
fb: conflicting fb hw usage inteldrmfb vs EFI VGA - removing generic driver
===========================
[ INFO: possible circular locking dependency detected ]
3.8.0-rc2-expert+ #2 Not tainted
-------------------------------------------------------
modprobe/603 is trying to acquire lock:
(console_lock){+.+.+.}, at: [<ffffffff812c869f>] unbind_con_driver+0x3f/0x200
but task is already holding lock:
((fb_notifier_list).rwsem){++++.+}, at: [<ffffffff810697c1>]
__blocking_notifier_call_chain+0x51/0xc0
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 ((fb_notifier_list).rwsem){++++.+}:
[<ffffffff81090a61>] __lock_acquire+0x3a1/0xb60
[<ffffffff810916ea>] lock_acquire+0x5a/0x70
[<ffffffff81557c97>] down_read+0x47/0x5c
[<ffffffff810697c1>] __blocking_notifier_call_chain+0x51/0xc0
[<ffffffff81069841>] blocking_notifier_call_chain+0x11/0x20
[<ffffffff81262a16>] fb_notifier_call_chain+0x16/0x20
[<ffffffff81264c20>] register_framebuffer+0x1c0/0x300
[<ffffffff81ac2bd4>] efifb_probe+0x40f/0x496
[<ffffffff81308fbe>] platform_drv_probe+0x3e/0x70
[<ffffffff81306f86>] driver_probe_device+0x76/0x240
[<ffffffff813071f3>] __driver_attach+0xa3/0xb0
[<ffffffff813051fd>] bus_for_each_dev+0x4d/0x90
[<ffffffff81306ae9>] driver_attach+0x19/0x20
[<ffffffff813066a0>] bus_add_driver+0x1a0/0x270
[<ffffffff81307882>] driver_register+0x72/0x170
[<ffffffff81308831>] platform_driver_register+0x41/0x50
[<ffffffff81308856>] platform_driver_probe+0x16/0xa0
[<ffffffff81ac2ece>] efifb_init+0x273/0x292
[<ffffffff810002da>] do_one_initcall+0x11a/0x170111 more lines