Re: [RFC][PATCH v2] perf: Fix perf_addr_filters_afjust()

[Leo Yan]

On Tue, Jun 23, 2026 at 11:14:26AM +0200, Peter Zijlstra wrote:
> 
>  - adjust lock order; since perf_event_addr_filters_apply() takes mmap_lock
>    inside child_mutex.
> 
>  - note that perf_event_mmap() is called by the thread doing the
>    mmap()/mprotect()/.. operation, but not the other threads in the address
>    space that might have inherited the same event.
> 
>  - have perf_addr_filters_adjust() iterate the child_list to find all other
>    events for tasks that have the same mm.
> 
>  - since this can now adjust addr_filter_ranges[] for remote events, make sure
>    to adjust things while holding ctx->lock; local_irq_disable() as implied by
>    the ifh->lock is no longer suffient to serialize against event scheduling.
> 
>  - per the previous locking order; perf_event_mmap(), which is called holding
>    mmap_lock, cannot take child_mutex, as such, make child_list RCU protected
>    and iterate under RCU.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>

Just verified this patch with Arm CoreSight:

  perf record -e cs_etm//u --filter 'filter traced_region @/root/test' -- /root/test

The workload forks a child process to inherited the event, also used
trace_printk() to confirm perf_event_addr_filters_adjust() has been hit.
No warning reported by LOCKDEP.

Tested-by: Leo Yan <leo.yan@xxxxxxx>

If you want me to try any specific test, pleaset let me know and I am
glad to give a run.

Maybe it is good to fix typo in the subject: s/afjust()/adjust()/.