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| author | Chris Wilson <chris@chris-wilson.co.uk> | 2020-02-27 11:57:05 +0300 |
|---|---|---|
| committer | Chris Wilson <chris@chris-wilson.co.uk> | 2020-02-28 17:05:33 +0300 |
| commit | a5af081d012e8b0ede5b1ef59a9c143067b45af6 (patch) | |
| tree | 520b3f037771a07abaf350e2455a2cdae3a45cf0 /drivers/gpu/drm/i915/i915_perf.c | |
| parent | 6875eb3ff5a37b73cd59bb6dcb6828ade1f62e66 (diff) | |
| download | linux-a5af081d012e8b0ede5b1ef59a9c143067b45af6.tar.xz | |
drm/i915/perf: Mark up the racy use of perf->exclusive_stream
Inside the general i915_oa_init_reg_state() we avoid using the
perf->mutex. However, we rely on perf->exclusive_stream being valid to
access at that point, and for that we have to control the race with
disabling perf. This relies on the disabling being a heavy barrier that
inspects all active contexts, after marking the perf->exclusive_stream
as not available. This should ensure that there are no more concurrent
accesses to the perf->exclusive_stream as we destroy it.
Mark up the races around the perf->exclusive_stream so that they stand
out much more. (And hopefully we will be running kcsan to start
validating that the only races we have are carefully controlled.)
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200227085723.1961649-2-chris@chris-wilson.co.uk
Diffstat (limited to 'drivers/gpu/drm/i915/i915_perf.c')
| -rw-r--r-- | drivers/gpu/drm/i915/i915_perf.c | 13 |
1 files changed, 7 insertions, 6 deletions
diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c index e34c79df6ebc..0838a12e2dc5 100644 --- a/drivers/gpu/drm/i915/i915_perf.c +++ b/drivers/gpu/drm/i915/i915_perf.c @@ -1405,8 +1405,10 @@ static void i915_oa_stream_destroy(struct i915_perf_stream *stream) /* * Unset exclusive_stream first, it will be checked while disabling * the metric set on gen8+. + * + * See i915_oa_init_reg_state() and lrc_configure_all_contexts() */ - perf->exclusive_stream = NULL; + WRITE_ONCE(perf->exclusive_stream, NULL); perf->ops.disable_metric_set(stream); free_oa_buffer(stream); @@ -2847,7 +2849,7 @@ static int i915_oa_stream_init(struct i915_perf_stream *stream, goto err_oa_buf_alloc; stream->ops = &i915_oa_stream_ops; - perf->exclusive_stream = stream; + WRITE_ONCE(perf->exclusive_stream, stream); ret = perf->ops.enable_metric_set(stream); if (ret) { @@ -2867,7 +2869,7 @@ static int i915_oa_stream_init(struct i915_perf_stream *stream, return 0; err_enable: - perf->exclusive_stream = NULL; + WRITE_ONCE(perf->exclusive_stream, NULL); perf->ops.disable_metric_set(stream); free_oa_buffer(stream); @@ -2893,12 +2895,11 @@ void i915_oa_init_reg_state(const struct intel_context *ce, { struct i915_perf_stream *stream; - /* perf.exclusive_stream serialised by lrc_configure_all_contexts() */ - if (engine->class != RENDER_CLASS) return; - stream = engine->i915->perf.exclusive_stream; + /* perf.exclusive_stream serialised by lrc_configure_all_contexts() */ + stream = READ_ONCE(engine->i915->perf.exclusive_stream); /* * For gen12, only CTX_R_PWR_CLK_STATE needs update, but the caller * is already doing that, so nothing to be done for gen12 here. |