RFR(s): 8143291: Remove redundant coding around os::exception_name
Thomas Stüfe
thomas.stuefe at gmail.com
Wed Nov 25 13:29:22 UTC 2015
Hi David,
new webrev:
http://cr.openjdk.java.net/~stuefe/webrevs/8143291/webrev.02/webrev/index.html
Changes:
1) added SIGSTKFLT
2) as per your suggestion, added os::get_signal_number() and moved
JVM_FindSignal to jvm.cpp, removing the different implementations from
jvm_<os>.cpp.
I still am not totally happy with adding os::get_signal_number() to
windows. I feel it is a bit confusing:
- we have os::get_signal_number() which takes Posix signal names (even on
Windows, even though signal support is almost nonexistent)
- we have os::exception_name(), which under windows returns the name of a
given machine exception (e.g. "EXCEPTION_ACCESS_VIOLATION") and under Posix
a signal name.
- we have os::Posix::get_signal_name(), which only exists on Posix.
But cleaning this up goes a bit beyond what I planned to so with my fix.
Kind Regards, Thomas
On Wed, Nov 25, 2015 at 10:13 AM, David Holmes <david.holmes at oracle.com>
wrote:
> Hi Thomas,
>
> On 25/11/2015 12:40 AM, Thomas Stüfe wrote:
>
>> Hi David,
>>
>> On Mon, Nov 23, 2015 at 7:26 AM, David Holmes <david.holmes at oracle.com
>> <mailto:david.holmes at oracle.com>> wrote:
>>
>> Hi Thomas,
>>
>> Looks good!
>>
>> On 20/11/2015 8:14 PM, Thomas Stüfe wrote:
>>
>> Hi David,
>>
>> here my second webrev:
>>
>>
>> http://cr.openjdk.java.net/~stuefe/webrevs/8143291/webrev.01/webrev/index.html
>>
>>
>> os_posix.cpp doesn't define SIGSTKFLT (currently defined for Linux
>> and AIX)
>>
>> I think we can we now move:
>>
>> JVM_ENTRY_NO_ENV(jint, JVM_FindSignal(const char *name))
>> return os::Posix::get_signal_number(name);
>> JVM_END
>>
>> into jvm.cpp (from jvm_<os>.cpp) - that would clean things up a bit
>> more. We can promote os::Posix::get_signal_number to be an os::
>> function (all platforms have signals, even windows) called from the
>> shared JVM_FindSignal - then create a Windows version in
>> os_windows.cpp by moving the code currently in jvm_windows.cpp
>> JVM_FindSignal.
>>
>>
>> I don't know... moving get_signal_number/name up into os:: seems kind of
>> a stretch.
>>
>
> But we already have a bunch of os:: level signal functions:
>
> static void signal_init();
> static void signal_init_pd();
> static void signal_notify(int signal_number);
> static void* signal(int signal_number, void* handler);
> static void signal_raise(int signal_number);
> static int signal_wait();
> static int signal_lookup();
>
> I would prefer to leave windows out of it for now because I
>> do not understand how windows signal handling (is there really any?)
>> corresponds to Structured Exception Handling.
>>
>
> This won't change any actual code execution on Windows, simply move the
> existing logic from one place to another.
>
> Cheers,
> David
> -----
>
> How about: adding a jvm_posix.cpp, moving JVM_FindSignal() from all
>> jvm_<linux|bsd|solaris|aix>.cpp to jvm_posix.cpp? That would be almost
>> as good...
>>
>> Kind Regards, Thomas
>>
>> Thanks,
>> David
>> -----
>>
>>
>> Remarks below.
>>
>> On Thu, Nov 19, 2015 at 12:56 PM, David Holmes
>> <david.holmes at oracle.com <mailto:david.holmes at oracle.com>
>> <mailto:david.holmes at oracle.com
>>
>> <mailto:david.holmes at oracle.com>>> wrote:
>>
>> Hi Thomas,
>>
>> I like the idea of this, but it will take me a little time
>> to check
>> all the details. More below ...
>>
>> On 19/11/2015 8:23 PM, Thomas Stüfe wrote:
>>
>> Hi,
>>
>> please take a look at this change.
>>
>> bug: https://bugs.openjdk.java.net/browse/JDK-8143291
>> webrev:
>>
>> http://cr.openjdk.java.net/~stuefe/webrevs/8143291/webrev.00/webrev/
>>
>> This fix does some cleanups around os::exception_name().
>>
>> - os::exception_name() is identical on all Posix
>> platforms (it
>> returns a
>> signal name string for a signal number), so it can be
>> merged into
>> os_posix.cpp
>>
>> - There is no need for a platform-specific
>> implementation, as we
>> have
>> already os::Posix::get_signal_name(). Use that instead of
>> platform-specific
>> solutions.
>>
>> - I added a function os::Posix::get_signal_number()
>> which is the
>> inverse of
>> os::Posix::get_signal_name().
>>
>> - Before, a signal-to-number table was kept in
>> jvm_<os>.cpp.
>> That was used
>> to implement os::exception_name() and also for
>> JVM_FindSignal
>> -> on AIX, I removed the coding altogether and used
>> os::Posix::get_signal_number() as a base for
>> JVM_FindSignal.
>> -> on the other Unices, I did not feel so confident,
>> because
>> strictly
>> spoken we may change the behaviour slightly to before:
>> os::Posix::get_signal_name() knows more signal names
>> than the
>> platform
>> specific tables knew before, so now
>> Signal.findSignal("<name>")
>> would
>> return more matches than before.
>>
>>
>> How so? If the additional names are platform specific then
>> they
>> won't exist at build time on the other platforms and so will
>> be
>> elided from the table.
>>
>>
>> I agree and changed jvm_bsd.cpp, jvm_linux.cpp and
>> jvm_solaris.cpp to
>> use os::Posix::get_signal_number for JVM_findSignal. That
>> removes more
>> duplicate code.
>>
>> BTW the existing Solaris code is incorrect when we start
>> building on
>> Solaris 11, so it would be good to use something that uses
>> the
>> actual build time signal value rather than the current
>> array based
>> approach.
>>
>>
>> Nice, that should be automatically fixed too then.
>>
>> Kind Regards, Thomas
>>
>> Thanks,
>> David
>>
>>
>> I am not sure whether I am overcautious here - should I
>> treat
>> the other
>> Unices the same way I treated AIX, i.e. implement
>> Signal.findSignal("<name>") -> JVM_FindSignal via
>> os::Posix::get_signal_number()? This would further
>> simplify the
>> coding.
>>
>> Oh, this fix also fixes an issue where
>> os::exception_name()
>> would return
>> NULL for an unknown signal number, but no caller ever
>> checks for
>> NULL
>> before printing the result. The new
>> os::exception_name() always
>> returns a
>> string and also distinguishes between "unknown but
>> valid signal" and
>> "invalid signal".
>>
>> Kind Regards, Thomas
>>
>>
>>
>>
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