Re: [PATCH] drm/amdgpu: replace mutex with spin_lock (V2)

["S, Shirish" <sshankar-5C7GfCeVMHo@public.gmane.org>]

On 6/22/2018 9:19 AM, S, Shirish wrote:
>
>
> On 6/22/2018 9:00 AM, Dave Airlie wrote:
>> On 31 May 2018 at 20:02, Shirish S <shirish.s@amd.com> wrote:
>>> mutex's lead to sleeps which should be avoided in
>>> atomic context.
>>> Hence this patch replaces it with the spin_locks.
>>>
>>> Below is the stack trace:
>> I'm not sure I really like this series of patches, going around
>> replacing ATOMIC and mutex with spinlocks
>> isn't something that should be done lightly,
>>
>> In all the patches I haven't seen what spin lock or what causes us to
>> be in an atomic state in the first
>> place and why it is necessary that we are in an atomic state for such
>> long sequences of code.
> We have root caused the issue and reverted all the patches in this 
> patch series that tend to replace
> mutex's with spinlock's.
I somehow noticed that this patch did not get reverted.
Please don't merge this patch.
Regards,
Shirish S
> Regards,
> Shirish S
>> Thanks,
>> Dave.
>>
>>> BUG: sleeping function called from invalid context at 
>>> kernel/locking/mutex.c:**
>>> 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
>>>
>>> V2: Added stack trace in commit message.
>>>
>>> Signed-off-by: Shirish S <shirish.s@amd.com>
>>> ---
>>>   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..54063e2 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@lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/amd-gfx
>

-- 
Regards,
Shirish S

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