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drm/i915/gem: Serialise debugfs i915_gem_objects with ctx->mutex

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Since the debugfs may peek into the GEM contexts as the corresponding
client/fd is being closed, we may try and follow a dangling pointer.
However, the context closure itself is serialised with the ctx->mutex,
so if we hold that mutex as we inspect the state coupled in the context,
we know the pointers within the context are stable and will remain valid
as we inspect their tables.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: CQ Tang <cq.tang@intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: stable@vger.kernel.org
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200723172119.17649-3-chris@chris-wilson.co.uk
(cherry picked from commit 102f5aa491)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
This commit is contained in:
Chris Wilson 2020-07-23 18:21:19 +01:00 committed by Rodrigo Vivi
parent cef8ce5528
commit 4fe9af8e88
1 changed files with 2 additions and 0 deletions
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2
drivers/gpu/drm/i915/i915_debugfs.c
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@ -326,6 +326,7 @@ static void print_context_stats(struct seq_file *m,
}
i915_gem_context_unlock_engines(ctx);
mutex_lock(&ctx->mutex);
if (!IS_ERR_OR_NULL(ctx->file_priv)) {
struct file_stats stats = {
.vm = rcu_access_pointer(ctx->vm),
@ -346,6 +347,7 @@ static void print_context_stats(struct seq_file *m,
print_file_stats(m, name, stats);
}
mutex_unlock(&ctx->mutex);
spin_lock(&i915->gem.contexts.lock);
list_safe_reset_next(ctx, cn, link);