[PATCH] drm: Don't allow interruptions when opening debugfs/crc

[Daniel Vetter]

On Fri, Apr 07, 2017 at 01:55:00PM +0200, Tomeu Vizoso wrote:
> On 04/07/2017 01:17 PM, Chris Wilson wrote:
> > The code does not like to be interrupted when waiting for the first
> > vblank after opening a debugfs/crc channel, so don't.
> > 
> > [66285.716870] WARNING: CPU: 1 PID: 16615 at drivers/gpu/drm/drm_debugfs_crc.c:185 crtc_crc_open+0x1d0/0x1f0 [drm]
> > [66285.716877] Modules linked in: i915 intel_powerclamp crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel cryptd intel_gtt i2c_algo_bit lpc_ich mfd_core drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops prime_numbers drm video button autofs4 sd_mod ahci libahci libata i2c_i801 scsi_mod i2c_designware_platform i2c_designware_core i2c_core
> > [66285.716929] CPU: 1 PID: 16615 Comm: kms_frontbuffer Not tainted 4.11.0-rc5+ #7
> > [66285.716935] Hardware name: GIGABYTE GB-BXBT-1900/MZBAYAB-00, BIOS F8 03/02/2016
> > [66285.716941] Call Trace:
> > [66285.716955]  dump_stack+0x4d/0x6f
> > [66285.716966]  __warn+0xc1/0xe0
> > [66285.716975]  warn_slowpath_null+0x18/0x20
> > [66285.717004]  crtc_crc_open+0x1d0/0x1f0 [drm]
> > [66285.717014]  ? wake_atomic_t_function+0x50/0x50
> > [66285.717024]  full_proxy_open+0xf0/0x1b0
> > [66285.717032]  ? full_proxy_release+0x80/0x80
> > [66285.717042]  do_dentry_open.isra.17+0x14b/0x2d0
> > [66285.717051]  vfs_open+0x42/0x60
> > [66285.717064]  path_openat+0x5e7/0x13d0
> > [66285.717074]  ? refcount_dec_and_test+0x11/0x20
> > [66285.717081]  ? down_read+0xd/0x30
> > [66285.717087]  do_filp_open+0x85/0xf0
> > [66285.717093]  ? __vfs_write+0x23/0x120
> > [66285.717100]  ? __alloc_fd+0x3a/0x170
> > [66285.717107]  do_sys_open+0x11e/0x1f0
> > [66285.717113]  ? do_sys_open+0x11e/0x1f0
> > [66285.717119]  SyS_openat+0xf/0x20
> > [66285.717125]  entry_SYSCALL_64_fastpath+0x17/0x98
> > [66285.717131] RIP: 0033:0x7f5f2235146a
> > [66285.717135] RSP: 002b:00007ffd892e6bc0 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
> > [66285.717142] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f5f2235146a
> > [66285.717147] RDX: 0000000000000000 RSI: 00007ffd892e6c40 RDI: 0000000000000006
> > [66285.717151] RBP: 00007ffd892e6b20 R08: 0000000000000000 R09: 000000000000000f
> > [66285.717156] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
> > [66285.717161] R13: 00007ffd892e6b10 R14: 0000000000000004 R15: 00000000007e61f4
> > 
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100610
> > Fixes: e8fa5671183c ("drm: crc: Wait for a frame before returning from open()")
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Tomeu Vizoso <tomeu.vizoso at collabora.com>
> > Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> 
> Reviewed-by: Tomeu Vizoso <tomeu.vizoso at collabora.com>
> 
> Sounds good to me, there isn't any good reason for the wait to be
> interruptible.

Applied to drm-misc-next, thanks.
-Daniel

> 
> Thanks,
> 
> Tomeu
> 
> > ---
> >  drivers/gpu/drm/drm_debugfs_crc.c | 6 +-----
> >  1 file changed, 1 insertion(+), 5 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_debugfs_crc.c b/drivers/gpu/drm/drm_debugfs_crc.c
> > index 1722d8f21449..aa13e734c9e5 100644
> > --- a/drivers/gpu/drm/drm_debugfs_crc.c
> > +++ b/drivers/gpu/drm/drm_debugfs_crc.c
> > @@ -177,13 +177,9 @@ static int crtc_crc_open(struct inode *inode, struct file *filep)
> >  	 * guess when this particular piece of HW will be ready to start
> >  	 * generating CRCs.
> >  	 */
> > -	ret = wait_event_interruptible_lock_irq(crc->wq,
> > -						crtc_crc_data_count(crc),
> > -						crc->lock);
> > +	wait_event_lock_irq(crc->wq, crtc_crc_data_count(crc), crc->lock);
> >  	spin_unlock_irq(&crc->lock);
> >  
> > -	WARN_ON(ret);
> > -
> >  	return 0;
> >  
> >  err_disable:
> > 
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch