[PATCH] drm/amdgpu: revert "fix deadlock of reservation between cs and gpu reset v2"

[Liu, Monk]

>The patch doesn't work at all:
1. The CS can still be blocked because of amdgpu_ctx_add_fence().
2. The order of submission isn't correct any more.
3. We could end up using freed up memory because we now drop the
   ctx reference to early.


I suddenly found that the parser->job is really a wild pointer:

    amdgpu_cs_parser_fini(p, 0, true);

    trace_amdgpu_cs_ioctl(job);
    amd_sched_entity_push_job(&job->base);

so "cs_parser_fini" cannot be called before "entity_push_job", that part is correct


but how to understand 1)

what do you mean "The CS can still be blocked because of amdgpu_ctx_add_fence()."


for 2)The order of submission isn't correct any more.

I think since the pointer "job" is already a dirty pointer, meaningless that  we talking about it if the order is correct ...


BR Monk



________________________________
From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> on behalf of Christian König <deathsimple at vodafone.de>
Sent: Tuesday, September 5, 2017 9:14:23 PM
To: amd-gfx at lists.freedesktop.org; Zhou, David(ChunMing)
Subject: [PATCH] drm/amdgpu: revert "fix deadlock of reservation between cs and gpu reset v2"

From: Christian König <christian.koenig at amd.com>

This reverts commit 10e709cb296c98424c03408d23e3addeddcd4088.

The patch doesn't work at all:
1. The CS can still be blocked because of amdgpu_ctx_add_fence().
2. The order of submission isn't correct any more.
3. We could end up using freed up memory because we now drop the
   ctx reference to early.

This needs to be fixed cleanly by doing the context handling after the BO
handling, but this is a larger task just avoid the obvious crashes for now.

Signed-off-by: Christian König <christian.koenig at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index b96776c..2db4010 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -1061,7 +1061,6 @@ static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,
         cs->out.handle = amdgpu_ctx_add_fence(p->ctx, ring, p->fence);
         job->uf_sequence = cs->out.handle;
         amdgpu_job_free_resources(job);
-       amdgpu_cs_parser_fini(p, 0, true);

         trace_amdgpu_cs_ioctl(job);
         amd_sched_entity_push_job(&job->base);
@@ -1120,10 +1119,7 @@ int amdgpu_cs_ioctl(struct drm_device *dev, void *data, struct drm_file *filp)
                 goto out;

         r = amdgpu_cs_submit(&parser, cs);
-       if (r)
-               goto out;

-       return 0;
 out:
         amdgpu_cs_parser_fini(&parser, r, reserved_buffers);
         return r;
--
2.7.4

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