Re: perf buildid-cache -p <path> question

[Thomas-Mich Richter <tmricht@linux.vnet.ibm.com>]

On 10/21/2017 05:17 PM, Masami Hiramatsu wrote:
> On Mon, 16 Oct 2017 14:24:11 +0200
> Thomas-Mich Richter <tmricht@linux.vnet.ibm.com> wrote:
> 
>> Maybe its me misunderstanding the buildid cache completely, but I ran into the following issue:
>>
>> I can add and remove files using the perf buildid-cache command. For example 
>> perf buildid-cache -a /usr/bin/tar adds the tar executable to the buildid-cache directory
>> .debug/usr/bin/tar 
>> and creates the <buildid> subdirectory
>> .debug/usr/bin/tar/e54c9946802bbbcb85760ffeb80700a5fd35ebe7/elf file.
>> Also a symbolic link from the directory
>> .debug/.buildid/e5/4c9946802bbbcb85760ffeb80700a5fd35ebe7 --> ../../usr/bin/tar/<buildid>/
>> is created.
>>
>> Command perf buildid-cache -a /usr/bin/tar
>> removes these entries.
>>
>> Now when I run ./perf buildid-cache -p /usr/bin
>> nothing happens and success is reported:
>> [root@s35lp76 perf]# ./perf buildid-cache -vp /usr/bin/
>> Removing bash /usr/bin/: Ok
>> Removing dbus-daemon /usr/bin/: Ok
>> Removing ls /usr/bin/: Ok
>> Removing readlink /usr/bin/: Ok
>> Removing sleep /usr/bin/: Ok
>> Removing tar /usr/bin/: Ok
>> Removing time /usr/bin/: Ok
>> Removing vim /usr/bin/: Ok
>> Purging /usr/bin/: Ok
> 
> How did you do that? 
> 
> At first, perf buildid-cache -p only accept target binary path, not a directory. Because -p (--purge) is for removing all "histrical" caches of target binary, that should be compatible to -r (--remove) option.
> 
> Anyway, if I tries below, I got just an error.
> 
> [mhiramat@devbox perf]$ rm -rf ~/.debug/
> [mhiramat@devbox perf]$ ./perf buildid-cache -a /usr/bin/tar
> [mhiramat@devbox perf]$ ./perf buildid-cache -vp /usr/bin
> Removing tar /usr/bin: FAIL
> Purging /usr/bin: FAIL
> /usr/bin wasn't in the cache
> 
> Because "/usr/bin" is a directory and not cached. Also, if I add /usr/bin as below, it's just refused.
> 
> [mhiramat@devbox perf]$ ./perf buildid-cache -a /usr/bin
> Couldn't add /usr/bin: Is a directory
> 
> So, I wonder how did you do that.

When you look at the patch I submitted, in function build_id_cache__purge_path()
you specify a fully qualified path name, for example /usr/bin/tar. This is a file
and it calls function build_id_cache__remove_file() to remove its entries in the cache.

However if this function gets something like /usr/bin it detects that this is
a directory (system call stat(2)) and calls build_id_cache__purge_path() recursively
to remove the contents of this directory.

PS: This is the same approach as in function rm_rf() which recusively calls itself
to remove all possible buidid entries of a binary.

Hope this helps.



> 
> Thank you,
> 

-- 
Thomas Richter, Dept 3303, IBM LTC Boeblingen Germany
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