Re: [RFC PATCH] drm: gpu: msm: forbid mem reclaim from reset

[Akhil P Oommen <akhilpo@oss.qualcomm.com>]

On 3/26/2026 7:24 AM, Sergey Senozhatsky wrote:
> On (26/01/27 16:33), Sergey Senozhatsky wrote:
>> We sometimes get into a situtation where GPU hangcheck fails to
>> recover GPU:
>>
>> [..]
>> msm_dpu ae01000.display-controller: [drm:hangcheck_handler] *ERROR* (IPv4: 1): hangcheck detected gpu lockup rb 0!
>> msm_dpu ae01000.display-controller: [drm:hangcheck_handler] *ERROR* (IPv4: 1): completed fence: 7840161
>> msm_dpu ae01000.display-controller: [drm:hangcheck_handler] *ERROR* (IPv4: 1): submitted fence: 7840162
>> msm_dpu ae01000.display-controller: [drm:hangcheck_handler] *ERROR* (IPv4: 1): hangcheck detected gpu lockup rb 0!
>> msm_dpu ae01000.display-controller: [drm:hangcheck_handler] *ERROR* (IPv4: 1): completed fence: 7840162
>> msm_dpu ae01000.display-controller: [drm:hangcheck_handler] *ERROR* (IPv4: 1): submitted fence: 7840163
>> [..]
>>
>> The problem is that msm_job worker is blocked on gpu->lock
>>
>> INFO: task ring0:155 blocked for more than 122 seconds.
>> Not tainted 6.6.99-08727-gaac38b365d2c #1
>> task:ring0 state:D stack:0 pid:155 ppid:2 flags:0x00000008
>> Call trace:
>> __switch_to+0x108/0x208
>> schedule+0x544/0x11f0
>> schedule_preempt_disabled+0x30/0x50
>> __mutex_lock_common+0x410/0x850
>> __mutex_lock_slowpath+0x28/0x40
>> mutex_lock+0x5c/0x90
>> msm_job_run+0x9c/0x140
>> drm_sched_main+0x514/0x938
>> kthread+0x114/0x138
>> ret_from_fork+0x10/0x20
>>
>> which is owned by recover worker, which is waiting for DMA fences
>> from a memory reclaim path, under the very same gpu->lock

I am still thinking if there is a better way to handle this. Btw, Rob
had a few fixes related to this area recently. Do you think those would
help in this scenario?

-Akhil

>>
>> INFO: task ring0:155 is blocked on a mutex likely owned by task gpu-worker:154.
>> task:gpu-worker state:D stack:0 pid:154 ppid:2 flags:0x00000008
>> Call trace:
>> __switch_to+0x108/0x208
>> schedule+0x544/0x11f0
>> schedule_timeout+0x1f8/0x770
>> dma_fence_default_wait+0x108/0x218
>> dma_fence_wait_timeout+0x6c/0x1c0
>> dma_resv_wait_timeout+0xe4/0x118
>> active_purge+0x34/0x98
>> drm_gem_lru_scan+0x1d0/0x388
>> msm_gem_shrinker_scan+0x1cc/0x2e8
>> shrink_slab+0x228/0x478
>> shrink_node+0x380/0x730
>> try_to_free_pages+0x204/0x510
>> __alloc_pages_direct_reclaim+0x90/0x158
>> __alloc_pages_slowpath+0x1d4/0x4a0
>> __alloc_pages+0x9f0/0xc88
>> vm_area_alloc_pages+0x17c/0x260
>> __vmalloc_node_range+0x1c0/0x420
>> kvmalloc_node+0xe8/0x108
>> msm_gpu_crashstate_capture+0x1e4/0x280
>> recover_worker+0x1c0/0x638
>> kthread_worker_fn+0x150/0x2d8
>> kthread+0x114/0x138
>>
>> So no one can make any further progress.
>>
>> Forbid recover/fault worker to enter memory reclaim (under
>> gpu->lock) to address this deadlock scenario.
>>
>> Cc: Tomasz Figa <tfiga@chromium.org>
>> Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
> 
> 
> Folks, can somebody please review/pickup this patch?  It solves a real
> (deadlock) problem that we observe in the field.
> 
> // keeping the patch body just in case
> 
>> ---
>>  drivers/gpu/drm/msm/msm_gpu.c | 11 +++++++++++
>>  1 file changed, 11 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
>> index 995549d0bbbc..ddcd9e1c217a 100644
>> --- a/drivers/gpu/drm/msm/msm_gpu.c
>> +++ b/drivers/gpu/drm/msm/msm_gpu.c
>> @@ -17,6 +17,7 @@
>>  #include <linux/string_helpers.h>
>>  #include <linux/devcoredump.h>
>>  #include <linux/sched/task.h>
>> +#include <linux/sched/mm.h>
>>  
>>  /*
>>   * Power Management:
>> @@ -469,6 +470,7 @@ static void recover_worker(struct kthread_work *work)
>>  	struct msm_gem_submit *submit;
>>  	struct msm_ringbuffer *cur_ring = gpu->funcs->active_ring(gpu);
>>  	char *comm = NULL, *cmd = NULL;
>> +	unsigned int noreclaim_flag;
>>  	struct task_struct *task;
>>  	int i;
>>  
>> @@ -506,6 +508,8 @@ static void recover_worker(struct kthread_work *work)
>>  			msm_gem_vm_unusable(submit->vm);
>>  	}
>>  
>> +	noreclaim_flag = memalloc_noreclaim_save();
>> +
>>  	get_comm_cmdline(submit, &comm, &cmd);
>>  
>>  	if (comm && cmd) {
>> @@ -524,6 +528,8 @@ static void recover_worker(struct kthread_work *work)
>>  	pm_runtime_get_sync(&gpu->pdev->dev);
>>  	msm_gpu_crashstate_capture(gpu, submit, NULL, comm, cmd);
>>  
>> +	memalloc_noreclaim_restore(noreclaim_flag);
>> +
>>  	kfree(cmd);
>>  	kfree(comm);
>>  
>> @@ -588,6 +594,7 @@ void msm_gpu_fault_crashstate_capture(struct msm_gpu *gpu, struct msm_gpu_fault_
>>  	struct msm_gem_submit *submit;
>>  	struct msm_ringbuffer *cur_ring = gpu->funcs->active_ring(gpu);
>>  	char *comm = NULL, *cmd = NULL;
>> +	unsigned int noreclaim_flag;
>>  
>>  	mutex_lock(&gpu->lock);
>>  
>> @@ -595,6 +602,8 @@ void msm_gpu_fault_crashstate_capture(struct msm_gpu *gpu, struct msm_gpu_fault_
>>  	if (submit && submit->fault_dumped)
>>  		goto resume_smmu;
>>  
>> +	noreclaim_flag = memalloc_noreclaim_save();
>> +
>>  	if (submit) {
>>  		get_comm_cmdline(submit, &comm, &cmd);
>>  
>> @@ -610,6 +619,8 @@ void msm_gpu_fault_crashstate_capture(struct msm_gpu *gpu, struct msm_gpu_fault_
>>  	msm_gpu_crashstate_capture(gpu, submit, fault_info, comm, cmd);
>>  	pm_runtime_put_sync(&gpu->pdev->dev);
>>  
>> +	memalloc_noreclaim_restore(noreclaim_flag);
>> +
>>  	kfree(cmd);
>>  	kfree(comm);
>>  
>> -- 
>> 2.53.0.rc1.217.geba53bf80e-goog
>>