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

Rachel Protacio rachel.protacio at oracle.com
Wed Oct 28 20:59:18 UTC 2015

Including serviceability-dev. Recap:

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/8138916.02 Bug: https://bugs.openjdk.java.net/browse/JDK-8138916

Includes own acceptance test, and passes JPRT and remote hotspot/test tests.

Thank you, Rachel

On 10/28/2015 4:08 PM, Rachel Protacio wrote:

Thanks for the review and all the feedback! Rachel

On 10/28/2015 4:05 PM, Dmitry Samersoff wrote: Rachel,

Looks good for me! -Dmitry On 2015-10-28 20:50, Rachel Protacio wrote: Thank you both. I've removed the re-declaration and added prefixlen to newbuflen. As for line 115, that line is not for the sake of recalculating prefixlen, but for writing the prefix to the buffer.

http://cr.openjdk.java.net/~rprotacio/8138916.02/ Thanks, Rachel On 10/28/2015 12:27 PM, Coleen Phillimore wrote: Dmitry, Thank you for reviewing and providing comments. The second version is better because of these things that I didn't notice until you pointed it out.

The malloc won't be frequent. I think it'll be okay and follows other coding patterns in the jvm. Thanks! Coleen On 10/28/15 12:09 PM, Dmitry Samersoff wrote: Coleen,

OK. I'm leaving it in good hands ;) -Dmitry On 2015-10-28 18:54, Coleen Phillimore wrote: Hi, I'm also reviewing this. I think this looks good. I don't think the solution to allocate a static buffer is very nice because it still has limits and we don't want to allocate something large on the stack. The malloc case is the infrequent case. If it becomes frequent we can increase LogBufferSize from 512.

I think 111 the assert is good because if the windows code is wrong (or the vscprintf does something wrong an unexpected) we can catch the error with the assert before writing over memory. I agree 116 shouldn't redeclare 'ret'. Otherwise, I think it looks really good and I don't need to see another revision. Thanks! Coleen

On 10/28/15 11:40 AM, Dmitry Samersoff wrote: Rachel, On 2015-10-28 17:48, Rachel Protacio wrote: Thank you for the comments, both Dmitry and Mikael. Replies inline. Modified webrev: http://cr.openjdk.java.net/~rprotacio/8138916.01/ 111 Assert is never happens on Windows, so it's better to move it to osposix 113 newbuflen doesn't account prefixlen 115 you may consider to use pre-calculated at ll. 108 prefix rather than calculate it again. 116 int ret redefined it causes a warning. -Dmitry

(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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