[BUG ARM64/perf] Perf record on hardware breakpoint causes application to hang

[Hekuang]

This problem can be reproduced as follows:

We know cat /proc/version will read the memory of symbol
linux_proc_banner, then we make a hardware memory access
breakpoint on that address.

on terminal 1:

  $ perf record -e mem:0x$(cat /proc/kallsyms|grep 
linux_proc_banner|cut -d " " -f 1):rw --no-buffer -a

on terminal 2:

  $ cat /proc/version

Then our 'cat' process on terminal 2 will be hanged, until we press
'^C' to stop perf from recording events.

The sample numbers recorded by perf is extraordinary too:

  [ perf record: Captured and wrote 0.879 MB perf.data (22691 samples) ]

The right result can be produced by removing the 'no-buffer'
argument in perf command line, and the result should be like
this:

  $ perf record -e mem:0x$(cat /proc/kallsyms|grep linux_proc_
                           banner|cut -d " " -f 1):rw  -a
  ^C
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.013 MB perf.data (10 samples) ]

Report this bug to you and hope for answers.

Thanks.