On 2019-01-07 12:00 p.m., Grodzovsky, Andrey wrote: > > > On 01/07/2019 11:53 AM, StDenis, Tom wrote: >> On 2019-01-07 11:51 a.m., Grodzovsky, Andrey wrote: >>> >>> On 01/07/2019 11:36 AM, StDenis, Tom wrote: >>>> On 2019-01-07 11:33 a.m., Grodzovsky, Andrey wrote: >>>>> On 01/07/2019 11:16 AM, Liu, Shaoyun wrote: >>>>>> I think it's reasonable to use the hive specific lock for hive specific functions. >>>>>> The changes is acked-by Shaoyun.liu < Shaoyun.liu@xxxxxxx> >>>>>> >>>>>> -----Original Message----- >>>>>> From: amd-gfx <amd-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of StDenis, Tom >>>>>> Sent: Monday, January 7, 2019 10:16 AM >>>>>> To: amd-gfx@xxxxxxxxxxxxxxxxxxxxx >>>>>> Cc: StDenis, Tom <Tom.StDenis@xxxxxxx> >>>>>> Subject: [PATCH] add missing mutex lock to amdgpu_get_xgmi_hive() (v2) >>>>>> >>>>>> v2: Move locks around in other functions so that this function can stand on its own. Also only hold the hive specific lock for add/remove device instead of the driver global lock so you can't add/remove devices in parallel from one hive. >>>>>> >>>>>> Signed-off-by: Tom St Denis <tom.stdenis@xxxxxxx> >>>>>> --- >>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 2 +- >>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.c | 36 ++++++++++++++-------- >>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.h | 2 +- >>>>>> 3 files changed, 25 insertions(+), 15 deletions(-) >>>>>> >>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c >>>>>> index 39d5d058b2c7..13d8e2ad2f7a 100644 >>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c >>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c >>>>>> @@ -3525,7 +3525,7 @@ int amdgpu_device_gpu_recover(struct amdgpu_device *adev, >>>>>> * by different nodes. No point also since the one node already executing >>>>>> * reset will also reset all the other nodes in the hive. >>>>>> */ >>>>>> - hive = amdgpu_get_xgmi_hive(adev); >>>>>> + hive = amdgpu_get_xgmi_hive(adev, 0); >>>>>> if (hive && adev->gmc.xgmi.num_physical_nodes > 1 && >>>>>> !mutex_trylock(&hive->hive_lock)) >>>>>> return 0; >>>>> Let's say i have device 0 in hive A and it just got a gpu reset and at >>>>> the same time device 1 is being added to same have though >>>>> amdgpu_xgmi_add_device, hive->hive_lock is acquired by this new device >>>>> being added and so gpu reset for device 0 bails out on >>>>> '!mutex_trylock(&hive->hive_lock))' without completing the reset. >>>>> Also in general i feel a bit uncomfortable about the confusing >>>>> acquisition scheme in the function and the fact that you take the >>>>> hive->hive_lock inside amdgpu_get_xgmi_hive but release is still outside >>>>> of the function. >>>> Is adding a device while resetting a device even a valid operation >>>> anyways? >>> In theory it's valid if you have hot pluggable devices >>>> I think this means more so that the reset logic is broken. Instead >>>> there should be a per-hive reset lock that is taken and that is tested >>>> instead. >>>> >>>> Tom >>> The hive->hive_lock was added exactly for this purpose and used only for >>> that purpose. Maybe the naming i gave it wasn't reflective of it's >>> purpose :) >> >> But the add/remove should use per-hive locks not the global lock... :-) >> >> (I'm honestly not trying to bike shed I just thought the get_hive >> function looked wrong :-)). >> >> Tom > > Totally agree with you, if Shayun (who origianlly added the global > xgmi_mutex) is fine with switching to per hive mutex then me too, I just > point out the problem with gpu reset and as you said we then need to > rename the existing hive_lock into reset_lock and then and another per > hive lock to do what you propose. Also - is there a way to not take the > hive lock inside amdgpu_get_xgmi_hive but release it outside ? AFAIK > it's an opening for problems where people use it but forget to call > release. I wanted to take the per-hive lock inside get_hive because it also takes the global lock so that add/remove couldn't happen in parallel. For instance, deleting the last node while adding a new node means the per-hive mutex could be in limbo (because remove will delete the lock). Adding a per-hive reset lock would fix the remaining issues no? Tom _______________________________________________ amd-gfx mailing list amd-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/amd-gfx
