RFR: JDK-8059586: hs_err report should treat redirected core pattern.

Thomas Stüfe thomas.stuefe at gmail.com
Mon Dec 1 12:57:44 UTC 2014

Hi Yasumasa,

On Mon, Dec 1, 2014 at 10:45 AM, Yasumasa Suenaga <yasuenag at gmail.com>

> Hi Thomas, David,
> Sorry, I didn't think about async signal safety.
>  That would work, VmError::report_and_die() is singlethreaded. At least
>> the part which dumps out the core file name.
> I think that signal handler (in this case) may run concurrency with
> other thread.
> If another thread calls malloc(3) in JNI, C Heap corruption may occur.
No, malloc(3) should be thread safe on our platforms. But this was not the
point. If I understood David right, he suggested using a static buffer
inside get_core_path() for assembling the core path, which would make
get_core_path() thread-unsafe (multiple threads calling it would get
garbled results). But as get_core_path() is only called from within
VmError::report_and_die() and that section is only ever executed by one
thread, Davids suggestion would still work.

> I want to rewrite a patch as below:
>  - Use async signal safety functions.
>    fopen -> open, fgets -> read, etc.
>  - Use O_BUFLEN for buffer size.
>    O_BUFLEN is defined to 2000 in ostream.hpp .
>    This macro is used in various points. VMError::coredump_message is
>    also defined with this value.
I think PATH_MAX is fine. I think O_BUFLEN was originally used as a max.
length of temporary buffers to assemble an output line. And then it spread
a bit. But your intend is to hold a path and using PATH_MAX clearly
documents this.
And, to really nitpick, right now you do not handle ERANGE with
get_current_path() (if the provided buffer is too small), which is probably
fine because it is improbable that a path is larger than PATH_MAX. But if
you change the size of the buffer to something which may be smaller than
PATH_MAX (O_BUFLEN), get_current_directory() may fail.

I like your patch, I think it could be a nice time safer when core_pattern
is something unusual. But I also see Staffans point of too-much-complexity.
So I will keep out of this discussion until the real Reviewers decided what
to do :)

Kind Regards, Thomas

More information about the hotspot-runtime-dev mailing list