RFR 4823133: RandomAccessFile.length() is not thread-safe (original) (raw)

Magnus Ihse Bursie magnus.ihse.bursie at oracle.com
Fri Dec 18 13:35:19 UTC 2015

On 2015-12-15 18:25, Martin Buchholz wrote:

FILEOFFSETBITS is generally an all-or-nothing thing, because it affects interoperability between translation units. It would be good to convert all of the JDK build to use -DFILEOFFSETBITS=64, but that would be a big job. So traditionally the JDK has instead used the functions made available via LARGEFILE64SOURCE. But that is also a JDK-wide job now, because every call to plain stat in the source code is broken on 32-bit systems with 64-bit inodes, which are becoming more common.

I recommend the FILEOFFSETBITS=64 strategy, but it's probably a job for build-dev, not core-libs-dev.

If I understand things correctly, then setting _FILE_OFFSET_BITS=64 would mean two things:

  1. Just pass this additional define to all C files being compiled (a build change)
  2. Update all calls to file operating functions to make sure the proper 64-bit types are used (changes in source code).

The change for 1) is a trivial one liner, while getting 2) correct is a serious undertaking in the source code. Such a change must be done by the component teams, not the build team. With that said, I think it is a reasonable change and I'll support it as much as I can. But as the division of labour is done here, it's not the work of the build team to go and make heavy modifications to the product source code.

/Magnus

On Tue, Dec 15, 2015 at 8:31 AM, Roger Riggs <Roger.Riggs at oracle.com> wrote: Hi Yvom, Minor comments: src/java.base/share/native/libjava/RandomAccessFile.c: - "length fail" might be clearer as "GetLength failed" src/java.base/unix/native/libjava/ioutilmd.c: - Please add a comment before the define of FILEOFFSETBITS to indicate where it is used and why it is there. - BTW, are there any unintended side effects? Perhaps a different issue but perhaps 64 bit offsets should be used everywhere src/java.base/windows/native/libjava/ioutilmd.c - Line 592: Using INVALIDHANDLEVALUE is better than -1 and is used elsewhere in the file BTW, Testing for invalid handle might be unnecessary since the call to GetFileSizeEx will fail if it is invalid, yielding the same result. Roger

On 12/10/2015 5:52 AM, vyom wrote: Hi All, Please review my changes for below bug. Bug: JDK-4823133 : RandomAccessFile.length() is not thread-safe Webrev:http://cr.openjdk.java.net/~vtewari/4823133/webrev0.0/ <http://cr.openjdk.java.net/%7Evtewari/4823133/webrev0.0/> This change ensure that length() does not temporarily changes the file pointer and it will make sure that there is no race condition in case of multi thread uses. Thanks, Vyom

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