Re: [PATCH v2] perf stat: Count kernel events in a group led by a tool event

[sashiko-bot@kernel.org]

> From: Hang Zhengyang <hang.zhengyang1010@gmail.com>
> 
> A tool event like user_time has no perf event in the kernel, but
> get_group_fd() still passes its fd, the /proc/stat fd, as the group_fd
> of the members.  The kernel rejects each member with EBADF and nothing
> is counted:
> 
>   $ perf stat -a -e '{user_time,cycles,instructions}' -- sleep 0.05
>                    0      user_time
>      <not supported>      cycles
>      <not supported>      instructions
> 
> Open the members with group_fd = -1, as the enable/disable code already
> assumes.  They are then on their own, so read them without
> PERF_FORMAT_GROUP and open them disabled like a leader, so that -D,
> --control and enable_on_exec still apply.  Keep reporting a broken
> group when the leader failed to open.
> 
>   $ perf stat -a -e '{user_time,cycles,instructions}' -- sleep 0.05
>                    0      user_time
>             38257394      cycles
>             21228043      instructions
> 
> The kernel events in such a group are no longer scheduled together.
> 
> Fixes: 6828d6929b76 ("perf evsel: Refactor tool events")
> Assisted-by: Claude:claude-opus-5-5
> Signed-off-by: Hang Zhengyang <hang.zhengyang1010@gmail.com>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261111-tool-pmu-leader-v2-1-3faa0fb98c51@gmail.com?part=1