coresight: etm4x: Don't trace PID for non-root PID namespace

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When runs in perf mode, the driver always enables the PID tracing.  This
can lead confusion when the profiling session runs in non-root PID
namespace, whereas it records the PIDs from the root PID namespace.

To avoid confusion for PID tracing, when runs in perf mode, this patch
changes to only enable PID tracing for root PID namespace.

As result, after apply this patch, the perf tool reports PID as '-1' for
all samples:

  # unshare --fork --pid perf record -e cs_etm// -m 64K,64K -a \
	-o perf_test.data -- uname
  # perf report -i perf_test.data --itrace=Zi1000i --stdio

  # Total Lost Samples: 0
  #
  # Samples: 94  of event 'instructions'
  # Event count (approx.): 94000
  #
  # Overhead  Command  Shared Object      Symbol
  # ........  .......  .................  ..............................
  #
      68.09%  :-1      [kernel.kallsyms]  [k] __sched_text_end
       3.19%  :-1      [kernel.kallsyms]  [k] hrtimer_interrupt
       2.13%  :-1      [kernel.kallsyms]  [k] __bitmap_and
       2.13%  :-1      [kernel.kallsyms]  [k] trace_vbprintk
       1.06%  :-1      [kernel.kallsyms]  [k] __fget_files
       1.06%  :-1      [kernel.kallsyms]  [k] __schedule
       1.06%  :-1      [kernel.kallsyms]  [k] __softirqentry_text_start
       1.06%  :-1      [kernel.kallsyms]  [k] __update_load_avg_cfs_rq
       1.06%  :-1      [kernel.kallsyms]  [k] __update_load_avg_se
       1.06%  :-1      [kernel.kallsyms]  [k] arch_counter_get_cntpct
       1.06%  :-1      [kernel.kallsyms]  [k] check_and_switch_context
       1.06%  :-1      [kernel.kallsyms]  [k] format_decode
       1.06%  :-1      [kernel.kallsyms]  [k] handle_percpu_devid_irq
       1.06%  :-1      [kernel.kallsyms]  [k] irq_enter_rcu
       1.06%  :-1      [kernel.kallsyms]  [k] irqtime_account_irq
       1.06%  :-1      [kernel.kallsyms]  [k] ktime_get
       1.06%  :-1      [kernel.kallsyms]  [k] ktime_get_coarse_real_ts64
       1.06%  :-1      [kernel.kallsyms]  [k] memmove
       1.06%  :-1      [kernel.kallsyms]  [k] perf_ioctl
       1.06%  :-1      [kernel.kallsyms]  [k] perf_output_begin
       1.06%  :-1      [kernel.kallsyms]  [k] perf_output_copy
       1.06%  :-1      [kernel.kallsyms]  [k] profile_tick
       1.06%  :-1      [kernel.kallsyms]  [k] sched_clock
       1.06%  :-1      [kernel.kallsyms]  [k] timerqueue_add
       1.06%  :-1      [kernel.kallsyms]  [k] trace_save_cmdline
       1.06%  :-1      [kernel.kallsyms]  [k] update_load_avg
       1.06%  :-1      [kernel.kallsyms]  [k] vbin_printf

Signed-off-by: Leo Yan <leo.yan@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20220204152403.71775-4-leo.yan@linaro.org

...

This commit is contained in:

Leo Yan 2022-02-04 23:24:02 +08:00 • committed by Suzuki K Poulose

parent 1314dd1971

commit aab473867f

1 changed files with 8 additions and 2 deletions

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drivers/hwtracing/coresight/coresight-etm4x-core.c

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