RFR: 8255917: runtime/cds/SharedBaseAddress.java failed "assert(reserved_rgn != 0LL) failed: No reserved region" [v4]

[Yumin Qi]

On Tue, 8 Dec 2020 17:16:29 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> If `useBaseAddress==false`, after the total_space is successfully mapped, subsequent operations mail fail. For example,
>> 
>> - `mapinfo->map_regions()` may fail to commit the necessary memory for doing `os::read()`.
>> - `mapinfo->validate_shared_path_table()` may fail because the runtime classpath is not compatible
>> 
>> In these cases, we need to call MetaspaceShared::release_reserved_spaces().
>> 
>>> Do you see that assert?
>> 
>> Hmm, I think we should add a new test for this specifically: `java -XX:ArchiveRelocationMode=1 -cp mispatched.jar` to force the failure in `mapinfo->validate_shared_path_table()`.
>> 
>>>  If you only care for windows, that tracing could suffice.
>> 
>> Since we are changing the `split` parameter for all platforms, I think we should test for all platforms, not just windows.
>
> The new test case can be something like this:
> 
> $ java -XX:DumpLoadedClassList=HelloWorld.classlist -cp HelloWorld.jar HelloWorld
> Hello World
> $ java -Xshare:dump -XX:SharedClassListFile=HelloWorld.classlist -cp HelloWorld.jar \
>        -XX:SharedArchiveFile=tmp.jsa -XX:SharedBaseAddress=0 
> $ touch XXX.jar
> $ java -Xshare:auto -XX:SharedArchiveFile=tmp.jsa -cp XXX.jar:HelloWorld.jar -Xlog:cds \
>        -showversion HelloWorld
> ...
> [0.034s][info][cds] Archive(s) were created with -XX:SharedBaseAddress=0. Always map at os-selected address.
> [0.034s][info][cds] Try to map archive(s) at an alternative address
> [0.034s][info][cds] Mapped static  region #0 at base 0x00007f21f7800000 top 0x00007f21f7806000 (MiscCode)
> [0.034s][info][cds] Mapped static  region #1 at base 0x00007f21f7806000 top 0x00007f21f7a1d000 (ReadWrite)
> [0.034s][info][cds] Mapped static  region #2 at base 0x00007f21f7a1d000 top 0x00007f21f7daf000 (ReadOnly)
> [0.048s][info][cds] UseSharedSpaces: shared class paths mismatch (hint: enable -Xlog:class+path=info to diagnose the failure)
> [0.048s][info][cds] Unmapping region #0 at base 0x00007f21f7800000 (MiscCode)
> [0.048s][info][cds] Unmapping region #1 at base 0x00007f21f7806000 (ReadWrite)
> [0.048s][info][cds] Unmapping region #2 at base 0x00007f21f7a1d000 (ReadOnly)
> [0.048s][info][cds] UseSharedSpaces: Unable to map shared spaces
> java version "16-internal" 2021-03-16
> Java(TM) SE Runtime Environment (slowdebug build 16-internal+0-adhoc.iklam.open)
> Java HotSpot(TM) 64-Bit Server VM (slowdebug build 16-internal+0-adhoc.iklam.open, mixed mode)
> Hello World
> You can set a breakpoint at `MetaspaceShared::release_reserved_spaces()` to make sure it's called with `total_rs`.
> 
> Note that `-Xshare:auto` must be used. 
> 
> If `-Xshare:on` is used, the VM will exit immediately without calling `MetaspaceShared::release_reserved_spaces()`. Most of the CDS tests are executed with `-Xshare:on`. That's why we didn't see the assert on Windows with Yumin's earlier patch -- in Mach5 tier 4, we run test/hotspot/jtreg/runtime/cds/appcds/BootClassPathMismatch.java with `-XX:ArchiveRelocationMode=1`, but the test itself would use with `-Xshare:on`.

When jar mismatched, say, -cp non-exist.jar (We could not use -cp no-exitst.jar:hello.jar since, once hello.jar the dump time jar found and matched, the non-exist.jar will be ignored, test showed it is OK), the output:
[0.035s][info ][cds] Mapped static  region #0 at base 0x00007f98e3800000 top 0x00007f98e3806000 (MiscCode)
[0.035s][info ][cds] Mapped static  region #1 at base 0x00007f98e3806000 top 0x00007f98e3a1e000 (ReadWrite)
[0.035s][info ][cds] Mapped static  region #2 at base 0x00007f98e3a1e000 top 0x00007f98e3db2000 (ReadOnly)
[0.049s][info ][cds] UseSharedSpaces: shared class paths mismatch (hint: enable -Xlog:class+path=info to diagnose the failure)
[0.049s][info ][cds] Unmapping region #0 at base 0x00007f98e3800000 (MiscCode)
[0.049s][info ][cds] Unmapping region #1 at base 0x00007f98e3806000 (ReadWrite)
[0.049s][info ][cds] Unmapping region #2 at base 0x00007f98e3a1e000 (ReadOnly)
[0.049s][debug][cds] Released shared space 0x00007f98e3800000
[0.049s][debug][cds] Released shared space (archive + class) 0x00007f98e3800000
[0.049s][info ][cds] UseSharedSpaces: Unable to map shared spaces

The repeat will be eliminated next version from here:
1489   } else {
1490     unmap_archive(static_mapinfo);
1491     unmap_archive(dynamic_mapinfo);
1492     log_debug(cds)("Released shared space " INTPTR_FORMAT, p2i(total_space_rs.base()));
1493     release_reserved_spaces(total_space_rs, archive_space_rs, class_space_rs);
1494   }

-------------

PR: https://git.openjdk.java.net/jdk/pull/1657