RFR: 8138916: Logging write function does not allow for long enough messages (original) (raw)

Rachel Protacio rachel.protacio at oracle.com
Wed Oct 28 14:48:09 UTC 2015

Thank you for the comments, both Dmitry and Mikael. Replies inline.

Modified webrev: http://cr.openjdk.java.net/~rprotacio/8138916.01/ (Retested and works fine.)

On 10/27/2015 7:52 AM, Dmitry Samersoff wrote:

Rachel,

In worst case (windows, overflow) the code would parse format string four times. You're right. I've added a check. New amount of times vnsprintf() is called: posix, fits => 1 posix, overflow => 2 windows, fits => 1 windows, overflow => 3 (the best performance we can get)

Also NEWCHEAPARRAY takes a lock and might become a performance bottleneck.

POSIX equivalent of vscprintf(fmt, args) is vsnprintf(NULL, 0, fmt, args) So it might be better to create os::logvcprintf(fmt, args), then write code at log.hpp as: int buflen = os::logvcprintf(fmt, args); assert(buflen < 2*pagesize, "Stack overflow in logging"); char buf[buflen]; vsprintf(buf, fmt, args); I don't think this would work anyway. A char[] needs a static size. Thanks, Rachel -Dmitry

On 2015-10-26 23:58, Rachel Protacio wrote: Hello, all, Please review this fix to the faulty write function from the Unified Logging framework. Summary: In logging/log.hpp, the logging vwrite function previously asserted that the buffer remains within 512 characters, which is too short for logging message of non-pre-determined length, e.g. for vtable and itable function names. Now, the function resizes the buffer to the appropriate length, asserting only that the resulting buffer is valid. Includes tag "logtest" to test that logging can print an output of 518 characters. Open webrev:http://cr.openjdk.java.net/~rprotacio/8138916/ Bug:https://bugs.openjdk.java.net/browse/JDK-8138916 Includes own acceptance test, and passes JPRT and remote hotspot/test tests. Thank you, Rachel

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