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.
