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

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

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.
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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