[PATCH] drm/amdgpu: replace mutex with spin_lock

[S, Shirish]

On 5/30/2018 8:51 PM, Deucher, Alexander wrote:
>> -----Original Message-----
>> From: amd-gfx [mailto:amd-gfx-bounces at lists.freedesktop.org] On Behalf
>> Of Shirish S
>> Sent: Wednesday, May 30, 2018 6:20 AM
>> To: amd-gfx at lists.freedesktop.org; Wentland, Harry
>> <Harry.Wentland at amd.com>; Zhu, Rex <Rex.Zhu at amd.com>
>> Cc: S, Shirish <Shirish.S at amd.com>
>> Subject: [PATCH] drm/amdgpu: replace mutex with spin_lock
>>
>> mutex's lead to sleeps which should be avoided in atomic context.
>> Hence this patch replaces it with the spin_locks.
>>
>> Signed-off-by: Shirish S <shirish.s at amd.com>
> Does this actually fix a bug or is it just to be safe?  Do actually call atom command tables in an atomic context?
I have re-spun V2 patch, with the stack trace so that you can see the 
path taken.

For reference below is the trace:

BUG: sleeping function called from invalid context at 
kernel/locking/mutex.c:238
in_atomic(): 1, irqs_disabled(): 1, pid: 89, name: kworker/u4:3
CPU: 1 PID: 89 Comm: kworker/u4:3 Tainted: G        W 4.14.43 #8
Workqueue: events_unbound commit_work
Call Trace:
  dump_stack+0x4d/0x63
  ___might_sleep+0x11f/0x12e
  mutex_lock+0x20/0x42
  amdgpu_atom_execute_table+0x26/0x72
  enable_disp_power_gating_v2_1+0x85/0xae
  dce110_enable_display_power_gating+0x83/0x1b1
  dce110_power_down_fe+0x4a/0x6d
  dc_post_update_surfaces_to_stream+0x59/0x87
  amdgpu_dm_do_flip+0x239/0x298
  amdgpu_dm_commit_planes.isra.23+0x379/0x54b
  ? drm_calc_timestamping_constants+0x14b/0x15c
  amdgpu_dm_atomic_commit_tail+0x4fc/0x5d2
  ? wait_for_common+0x5b/0x69
  commit_tail+0x42/0x64
  process_one_work+0x1b0/0x314
  worker_thread+0x1cb/0x2c1
  ? create_worker+0x1da/0x1da
  kthread+0x156/0x15e
  ? kthread_flush_work+0xea/0xea
  ret_from_fork+0x22/0x40

Its caused when a BUG hit in the kernel.

Thanks & Regards,
Shirish S
> Alex
>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c | 2 +-
>>   drivers/gpu/drm/amd/amdgpu/atom.c            | 4 ++--
>>   drivers/gpu/drm/amd/amdgpu/atom.h            | 3 ++-
>>   3 files changed, 5 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
>> index bf872f6..ba3d4b9 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_atombios.c
>> @@ -2033,7 +2033,7 @@ int amdgpu_atombios_init(struct amdgpu_device
>> *adev)
>>   		return -ENOMEM;
>>   	}
>>
>> -	mutex_init(&adev->mode_info.atom_context->mutex);
>> +	spin_lock_init(&adev->mode_info.atom_context->lock);
>>   	if (adev->is_atom_fw) {
>>   		amdgpu_atomfirmware_scratch_regs_init(adev);
>>   		amdgpu_atomfirmware_allocate_fb_scratch(adev);
>> diff --git a/drivers/gpu/drm/amd/amdgpu/atom.c
>> b/drivers/gpu/drm/amd/amdgpu/atom.c
>> index 69500a8..bfd98f0 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/atom.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/atom.c
>> @@ -1261,7 +1261,7 @@ int amdgpu_atom_execute_table(struct
>> atom_context *ctx, int index, uint32_t * pa  {
>>   	int r;
>>
>> -	mutex_lock(&ctx->mutex);
>> +	spin_lock(&ctx->lock);
>>   	/* reset data block */
>>   	ctx->data_block = 0;
>>   	/* reset reg block */
>> @@ -1274,7 +1274,7 @@ int amdgpu_atom_execute_table(struct
>> atom_context *ctx, int index, uint32_t * pa
>>   	ctx->divmul[0] = 0;
>>   	ctx->divmul[1] = 0;
>>   	r = amdgpu_atom_execute_table_locked(ctx, index, params);
>> -	mutex_unlock(&ctx->mutex);
>> +	spin_unlock(&ctx->lock);
>>   	return r;
>>   }
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/atom.h
>> b/drivers/gpu/drm/amd/amdgpu/atom.h
>> index a391709..cdfb0d0 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/atom.h
>> +++ b/drivers/gpu/drm/amd/amdgpu/atom.h
>> @@ -26,6 +26,7 @@
>>   #define ATOM_H
>>
>>   #include <linux/types.h>
>> +#include <linux/spinlock_types.h>
>>   #include <drm/drmP.h>
>>
>>   #define ATOM_BIOS_MAGIC		0xAA55
>> @@ -125,7 +126,7 @@ struct card_info {
>>
>>   struct atom_context {
>>   	struct card_info *card;
>> -	struct mutex mutex;
>> +	spinlock_t lock;
>>   	void *bios;
>>   	uint32_t cmd_table, data_table;
>>   	uint16_t *iio;
>> --
>> 2.7.4
>>
>> _______________________________________________
>> amd-gfx mailing list
>> amd-gfx at lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/amd-gfx

-- 
Regards,
Shirish S

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