[3.8.y.z extended stable] Patch "drm/cirrus: do not attempt to acquire a reservation while in an" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    drm/cirrus: do not attempt to acquire a reservation while in an

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.18.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 60456cf145467a24f5ae14065df8d54bc29f40af Mon Sep 17 00:00:00 2001
From: Maarten Lankhorst <m.b.lankhorst at gmail.com>
Date: Thu, 27 Jun 2013 13:38:24 +0200
Subject: drm/cirrus: do not attempt to acquire a reservation while in an
 interrupt handler

commit 19d4b72c0c22c14900313f89765c5f7ef0a2718a upstream.

Mutexes should not be acquired in interrupt context. While the trylock
fastpath is arguably safe on all implementations, the slowpath
unlock path definitely isn't. This fixes the following lockdep splat:

[   13.044313] ------------[ cut here ]------------
[   13.044367] WARNING: at /c/kernel-tests/src/tip/kernel/mutex.c:858 mutex_trylock+0x87/0x220()
[   13.044378] DEBUG_LOCKS_WARN_ON(in_interrupt())
[   13.044378] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.10.0-rc4-00296-ga2963dd #20
[   13.044379] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007
[   13.044390]  0000000000000009 ffff88000de039f8 ffffffff81fc86d5 ffff88000de03a38
[   13.044395]  ffffffff810d511b ffff880000000018 ffff88000f33c690 0000000000000001
[   13.044398]  00000000000003f0 ffff88000f4677c8 0000000000000000 ffff88000de03a98
[   13.044400] Call Trace:
[   13.044412]  <IRQ>  [<ffffffff81fc86d5>] dump_stack+0x19/0x1b
[   13.044441]  [<ffffffff810d511b>] warn_slowpath_common+0x6b/0x90
[   13.044445]  [<ffffffff810d51a6>] warn_slowpath_fmt+0x46/0x50
[   13.044448]  [<ffffffff81fd34d7>] mutex_trylock+0x87/0x220
[   13.044482]  [<ffffffff8186484d>] cirrus_dirty_update+0x1cd/0x330
[   13.044486]  [<ffffffff818649e8>] cirrus_imageblit+0x38/0x50
[   13.044506]  [<ffffffff8165782e>] soft_cursor+0x22e/0x240
[   13.044510]  [<ffffffff81656c31>] bit_cursor+0x581/0x5b0
[   13.044525]  [<ffffffff815de9f4>] ? vsnprintf+0x124/0x670
[   13.044529]  [<ffffffff81651333>] ? get_color.isra.16+0x43/0x130
[   13.044532]  [<ffffffff81653fca>] fbcon_cursor+0x18a/0x1d0
[   13.044535]  [<ffffffff816566b0>] ? update_attr.isra.2+0xa0/0xa0
[   13.044556]  [<ffffffff81754b82>] hide_cursor+0x32/0xa0
[   13.044565]  [<ffffffff81755bd3>] vt_console_print+0x103/0x3b0
[   13.044569]  [<ffffffff810d58ac>] ? print_time+0x9c/0xb0
[   13.044576]  [<ffffffff810d5960>] ? print_prefix+0xa0/0xc0
[   13.044580]  [<ffffffff810d63f6>] call_console_drivers.constprop.6+0x146/0x1f0
[   13.044593]  [<ffffffff815f9b38>] ? do_raw_spin_unlock+0xc8/0x100
[   13.044597]  [<ffffffff810d6f27>] console_unlock+0x2f7/0x460
[   13.044600]  [<ffffffff810d787a>] vprintk_emit+0x59a/0x5e0
[   13.044615]  [<ffffffff81fb676c>] printk+0x4d/0x4f
[   13.044650]  [<ffffffff82ba5511>] print_local_APIC+0x28/0x41c
[   13.044672]  [<ffffffff8114db55>] generic_smp_call_function_single_interrupt+0x145/0x2b0
[   13.044688]  [<ffffffff8106f9e7>] smp_call_function_single_interrupt+0x27/0x40
[   13.044697]  [<ffffffff81fd8f72>] call_function_single_interrupt+0x72/0x80
[   13.044707]  <EOI>  [<ffffffff81078166>] ? native_safe_halt+0x6/0x10
[   13.044717]  [<ffffffff811425cd>] ? trace_hardirqs_on+0xd/0x10
[   13.044738]  [<ffffffff8104f669>] default_idle+0x59/0x120
[   13.044742]  [<ffffffff810501e8>] arch_cpu_idle+0x18/0x40
[   13.044754]  [<ffffffff811320c5>] cpu_startup_entry+0x235/0x410
[   13.044763]  [<ffffffff81f9e781>] rest_init+0xd1/0xe0
[   13.044766]  [<ffffffff81f9e6b5>] ? rest_init+0x5/0xe0
[   13.044778]  [<ffffffff82b93ec2>] start_kernel+0x425/0x493
[   13.044781]  [<ffffffff82b93810>] ? repair_env_string+0x5e/0x5e
[   13.044786]  [<ffffffff82b93595>] x86_64_start_reservations+0x2a/0x2c
[   13.044789]  [<ffffffff82b93688>] x86_64_start_kernel+0xf1/0x100
[   13.044799] ---[ end trace 113ad28772af4058 ]---

Reported-by: Fengguang Wu <fengguang.wu at intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst at canonical.com>
Signed-off-by: Dave Airlie <airlied at redhat.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/gpu/drm/cirrus/cirrus_fbdev.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/cirrus/cirrus_fbdev.c b/drivers/gpu/drm/cirrus/cirrus_fbdev.c
index 1e64d6f..4202ff5 100644
--- a/drivers/gpu/drm/cirrus/cirrus_fbdev.c
+++ b/drivers/gpu/drm/cirrus/cirrus_fbdev.c
@@ -24,7 +24,7 @@ static void cirrus_dirty_update(struct cirrus_fbdev *afbdev,
 	struct cirrus_bo *bo;
 	int src_offset, dst_offset;
 	int bpp = (afbdev->gfb.base.bits_per_pixel + 7)/8;
-	int ret;
+	int ret = -EBUSY;
 	bool unmap = false;
 	bool store_for_later = false;
 	int x2, y2;
@@ -38,7 +38,8 @@ static void cirrus_dirty_update(struct cirrus_fbdev *afbdev,
 	 * then the BO is being moved and we should
 	 * store up the damage until later.
 	 */
-	ret = cirrus_bo_reserve(bo, true);
+	if (!in_interrupt())
+		ret = cirrus_bo_reserve(bo, true);
 	if (ret) {
 		if (ret != -EBUSY)
 			return;
--
1.8.3.2