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| |
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| under the terms of the GNU General Public License version 2 only, as |
| published by the Free Software Foundation. |
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| |
| DESCRIPTION |
| |
| This is a lock coarsening test. There are 2 threads, trying to acquire a shared |
| resource. The 1st thread has a number of adjacent lock that are subject to lock |
| coarsening: |
| |
| ... |
| |
| synchronized( lock ) |
| { |
| lock.foo(); |
| } |
| |
| // (*) |
| |
| synchronized( lock ) |
| { |
| lock.foo(); |
| } |
| |
| ... |
| |
| |
| The test is written in such a way, that thread 2 will acquire the lock, if and |
| only if thread 1 is somewhere at point (*). Therefore, the fact that lock |
| coarsening occurred is described by the condition (numAcquiredLocks != 0). |
| |
| IMPLEMENTATION |
| The test has one parameter, -eliminateLocks, that tells whether the JVM option |
| -XX:+EliminateLocks has been specified, so running the test without |
| -eliminateLocks checks that lock coarsening didn't occur, and running it with |
| this option check that lock coarsening occurred. |
| |
| Some hacks have been made to force JIT compile the method doit() (see comments in |
| the source). |
| |
| FAILURE ANALYSIS |
| If test fails try to run it with -XX:+PrintOptoAssembly and -XX:+LogCompilation |
| to understand if this is a test or product bug. |
| |
| If compiled code of Thread_1::doit method have lot of locks that surround each |
| lock.foo() then coarsening did not happen and this is a product bug. |
| |
| If lock coarsening occurs but not triggered by test then it's a test bug |
| that should be investigated. One of such problems could be caused if method doit() |
| was not compiled due to insufficient warm-up iterations. Also there may be a product bug |
| in compilation. |
