Re: [igt-dev] [PATCH i-g-t 03/12] tools/intel_gpu_top: Restore user friendly error message

[Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>]

On Thu, Sep 28, 2023 at 09:16:23AM +0100, Tvrtko Ursulin wrote:
>
>On 27/09/2023 21:13, Umesh Nerlige Ramappa wrote:
>>On Fri, Sep 22, 2023 at 02:44:28PM +0100, Tvrtko Ursulin wrote:
>>>From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>>
>>>We have a nice error message displayed when an user with insufficient
>>>permissions tries to run the tool, but that got lost while Meteorlake
>>>support was added. Bring it back in.
>>>
>>>Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>>Cc: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
>>>---
>>>tools/intel_gpu_top.c | 10 +++++++---
>>>1 file changed, 7 insertions(+), 3 deletions(-)
>>>
>>>diff --git a/tools/intel_gpu_top.c b/tools/intel_gpu_top.c
>>>index 87e9681e53b4..e01355f90458 100644
>>>--- a/tools/intel_gpu_top.c
>>>+++ b/tools/intel_gpu_top.c
>>>@@ -554,9 +554,11 @@ static int get_num_gts(uint64_t type)
>>>
>>>        close(fd);
>>>    }
>>>-    assert(!errno || errno == ENOENT);
>>>-    assert(cnt > 0);
>>>-    errno = 0;
>>>+
>>>+    if (!cnt)
>>>+        cnt = errno;
>>>+    else
>>>+        errno = 0;
>>
>>ENOENT is the only way this logic is checking for num_gts.
>>
>>In this case error is propagated only if cnt == 0. What if cnt=1 and 
>>we get an error (other than ENOENT)? Should we ignore that?
>
>If cnt >= 1 then at least one tile was found so the errno happened 
>while probing for further tiles. So on single tile parts it can be 
>ignored.

I am actually only referring to single tile parts. The for loop iterates 
over MAX_GTs (4), so I am expecting an ENOENT from a single tile part 
when cnt >= 1. Anything else is an error/failure that we should flag.

> On multi-tile parts it cannot really happen, or even if it happens 
>situation would simply be "why is only one tile showing". If we want to 
>cover this impossible/unlikely case then maybe like this:
>
>	if (!cnt || (errno && errno != ENOENT))
>		cnt = -errno;

If you agree to the above logic, then this condition should do the 
trick.

Regards,
Umesh
>
>>I had something like this in mind for the regression (and sorry this 
>>fell through the cracks)
>>
>>https://patchwork.freedesktop.org/patch/541406/?series=118973&rev=1
>
>Oh back in June!
>
>I think yours work too, in which case it's a matter of a style choice 
>with which one to go. I don't have a strong preference - above would 
>be a bit more compact, while I think it still succinctly expresses the 
>failure condition ("nothing found or unexpected error while probing 
>for remote tiles").
>
>Regards,
>
>Tvrtko
>
>>
>>Regards,
>>Umesh
>>
>>>
>>>    return cnt;
>>>}
>>>@@ -590,6 +592,8 @@ static int pmu_init(struct engines *engines)
>>>    engines->fd = -1;
>>>    engines->num_counters = 0;
>>>    engines->num_gts = get_num_gts(type);
>>>+    if (engines->num_gts <= 0)
>>>+        return -1;
>>>
>>>    engines->irq.config = I915_PMU_INTERRUPTS;
>>>    fd = _open_pmu(type, engines->num_counters, &engines->irq, 
>>>engines->fd);
>>>-- 
>>>2.39.2
>>>