Integrated: 8277441: CompileQueue::add fails with assert(_last->next() == __null) failed: not last

[Tobias Hartmann]

On Mon, 22 Nov 2021 13:57:21 GMT, Tobias Hartmann <thartmann at openjdk.org> wrote:

> In the rare case that the compiler threads fail during initialization or the code cache is full and flushing is disabled, we completely disable JIT compilation and shut down the compiler runtime:
> https://github.com/openjdk/jdk/blob/2f4b5405f0b53782f3ed5274f68b31eb968efb6d/src/hotspot/share/compiler/compileBroker.cpp#L1813-L1817
> 
> In the process, we free all compiler queues and set `CompileQueue::_first` to `NULL` and put the `CompileTasks` on the free list: https://github.com/openjdk/jdk/blob/2f4b5405f0b53782f3ed5274f68b31eb968efb6d/src/hotspot/share/compiler/compileTask.cpp#L84
> 
> In rare cases, although compilation is disabled, another waiting thread might still call `CompileQueue::add`. That code then fails because `_last != NULL` and `_last->next()` is set to `_task_free_list`. 
> https://github.com/openjdk/jdk/blob/2f4b5405f0b53782f3ed5274f68b31eb968efb6d/src/hotspot/share/compiler/compileBroker.cpp#L362-L369
> 
> The fix is to set `_last` to `NULL` in `CompileQueue::free_all`. Adding to the compile queue then succeeds which is harmless because queues have only been freed to make the compiler threads exit faster:
> https://github.com/openjdk/jdk/blob/2f4b5405f0b53782f3ed5274f68b31eb968efb6d/src/hotspot/share/compiler/compileBroker.cpp#L1823
> 
> The test that triggered this will be added with [PR 6364](https://github.com/openjdk/jdk/pull/6364). I verified that it now passes.
> 
> Thanks,
> Tobias

This pull request has now been integrated.

Changeset: 90f96fb4
Author:    Tobias Hartmann <thartmann at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/90f96fb4db174e50cc2510f292fe69fc995add26
Stats:     1 line in 1 file changed: 1 ins; 0 del; 0 mod

8277441: CompileQueue::add fails with assert(_last->next() == __null) failed: not last

Reviewed-by: chagedorn, neliasso

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PR: https://git.openjdk.java.net/jdk/pull/6503