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drm/i915: Make GEM contexts track DRM clients
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If we make GEM contexts keep a reference to i915_drm_client for the whole
of their lifetime, we can consolidate the current task pid and name usage
by getting it from the client.

v2: Don't bother supporting selftests contexts from debugfs. (Chris)
v3 (Lucas): Finish constructing ctx before adding it to the list
v4 (Ram): Rebase on upstream

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Aravind Iddamsetty <aravind.iddamsetty@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20210123153733.18139-4-chris@chris-wilson.co.uk
Link: https://patchwork.freedesktop.org/patch/msgid/20210124153136.19124-4-chris@chris-wilson.co.uk
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Tvrtko Ursulin authored and Chris Wilson committed Jan 24, 2021
1 parent 12d52c7 commit d8b049b
Showing 3 changed files with 30 additions and 25 deletions.
20 changes: 14 additions & 6 deletions drivers/gpu/drm/i915/gem/i915_gem_context.c
Original file line number Diff line number Diff line change
@@ -343,13 +343,14 @@ void i915_gem_context_release(struct kref *ref)
trace_i915_context_free(ctx);
GEM_BUG_ON(!i915_gem_context_is_closed(ctx));

mutex_destroy(&ctx->engines_mutex);
mutex_destroy(&ctx->lut_mutex);
if (ctx->client)
i915_drm_client_put(ctx->client);

if (ctx->timeline)
intel_timeline_put(ctx->timeline);

put_pid(ctx->pid);
mutex_destroy(&ctx->engines_mutex);
mutex_destroy(&ctx->lut_mutex);
mutex_destroy(&ctx->mutex);

kfree_rcu(ctx, rcu);
@@ -888,6 +889,7 @@ static int gem_context_register(struct i915_gem_context *ctx,
u32 *id)
{
struct drm_i915_private *i915 = ctx->i915;
struct i915_drm_client *client;
struct i915_address_space *vm;
int ret;

@@ -899,23 +901,29 @@ static int gem_context_register(struct i915_gem_context *ctx,
WRITE_ONCE(vm->file, fpriv); /* XXX */
mutex_unlock(&ctx->mutex);

ctx->pid = get_task_pid(current, PIDTYPE_PID);
client = i915_drm_client_get(fpriv->client);

rcu_read_lock();
snprintf(ctx->name, sizeof(ctx->name), "%s[%d]",
current->comm, pid_nr(ctx->pid));
i915_drm_client_name(client),
pid_nr(i915_drm_client_pid(client)));
rcu_read_unlock();

/* And finally expose ourselves to userspace via the idr */
ret = xa_alloc(&fpriv->context_xa, id, ctx, xa_limit_32b, GFP_KERNEL);
if (ret)
goto err_pid;

ctx->client = client;

spin_lock(&i915->gem.contexts.lock);
list_add_tail(&ctx->link, &i915->gem.contexts.list);
spin_unlock(&i915->gem.contexts.lock);

return 0;

err_pid:
put_pid(fetch_and_zero(&ctx->pid));
i915_drm_client_put(client);
return ret;
}

13 changes: 3 additions & 10 deletions drivers/gpu/drm/i915/gem/i915_gem_context_types.h
Original file line number Diff line number Diff line change
@@ -96,19 +96,12 @@ struct i915_gem_context {
*/
struct i915_address_space __rcu *vm;

/**
* @pid: process id of creator
*
* Note that who created the context may not be the principle user,
* as the context may be shared across a local socket. However,
* that should only affect the default context, all contexts created
* explicitly by the client are expected to be isolated.
*/
struct pid *pid;

/** link: place with &drm_i915_private.context_list */
struct list_head link;

/** client: struct i915_drm_client */
struct i915_drm_client *client;

/**
* @ref: reference count
*
22 changes: 13 additions & 9 deletions drivers/gpu/drm/i915/i915_gpu_error.c
Original file line number Diff line number Diff line change
@@ -1240,7 +1240,9 @@ static void record_request(const struct i915_request *request,

ctx = rcu_dereference(request->context->gem_context);
if (ctx)
erq->pid = pid_nr(ctx->pid);
erq->pid = I915_SELFTEST_ONLY(!ctx->client) ?
0 :
pid_nr(i915_drm_client_pid(ctx->client));
}
rcu_read_unlock();
}
@@ -1261,23 +1263,25 @@ static bool record_context(struct i915_gem_context_coredump *e,
const struct i915_request *rq)
{
struct i915_gem_context *ctx;
struct task_struct *task;
bool simulated;

rcu_read_lock();

ctx = rcu_dereference(rq->context->gem_context);
if (ctx && !kref_get_unless_zero(&ctx->ref))
ctx = NULL;
rcu_read_unlock();
if (!ctx)
if (!ctx) {
rcu_read_unlock();
return true;
}

rcu_read_lock();
task = pid_task(ctx->pid, PIDTYPE_PID);
if (task) {
strcpy(e->comm, task->comm);
e->pid = task->pid;
if (I915_SELFTEST_ONLY(!ctx->client)) {
strcpy(e->comm, "[kernel]");
} else {
strcpy(e->comm, i915_drm_client_name(ctx->client));
e->pid = pid_nr(i915_drm_client_pid(ctx->client));
}

rcu_read_unlock();

e->sched_attr = ctx->sched;

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