RFR: JDK-8258606: os::print_signal_handlers() should resolve the function name of the handlers

[Thomas Stuefe]

On Mon, 21 Dec 2020 09:07:07 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> This patch changes the printout for our signal handlers in hs-err files and in `jcmd VM.info` to show the function names of the handlers. This is also interesting for CheckJNI.
>> 
>> Before:
>> Signal Handlers:
>> SIGSEGV: [libjvm.so+0xbb8ff0], sa_mask[0]=11111111011111111101111111111110, sa_flags=SA_RESTART|SA_SIGINFO
>> SIGBUS: [libjvm.so+0xbb8ff0], sa_mask[0]=11111111011111111101111111111110, sa_flags=SA_RESTART|SA_SIGINFO
>> SIGFPE: [libjvm.so+0xbb8ff0], sa_mask[0]=11111111011111111101111111111110, sa_flags=SA_RESTART|SA_SIGINFO
>> SIGPIPE: [libjvm.so+0xbb8ff0], sa_mask[0]=11111111011111111101111111111110, sa_flags=SA_RESTART|SA_SIGINFO
>> SIGXFSZ: [libjvm.so+0xbb8ff0], sa_mask[0]=11111111011111111101111111111110, sa_flags=SA_RESTART|SA_SIGINFO
>> SIGILL: [libjvm.so+0xbb8ff0], sa_mask[0]=11111111011111111101111111111110, sa_flags=SA_RESTART|SA_SIGINFO
>> SIGUSR2: [libjvm.so+0xbb8e90], sa_mask[0]=00000000000000000000000000000000, sa_flags=SA_RESTART|SA_SIGINFO
>> SIGHUP: [libjvm.so+0xbb95b0], sa_mask[0]=11111111011111111101111111111110, sa_flags=SA_RESTART|SA_SIGINFO
>> SIGINT: [libjvm.so+0xbb95b0], sa_mask[0]=11111111011111111101111111111110, sa_flags=SA_RESTART|SA_SIGINFO
>> SIGTERM: [libjvm.so+0xbb95b0], sa_mask[0]=11111111011111111101111111111110, sa_flags=SA_RESTART|SA_SIGINFO
>> SIGQUIT: [libjvm.so+0xbb95b0], sa_mask[0]=11111111011111111101111111111110, sa_flags=SA_RESTART|SA_SIGINFO
>> 
>> Now:
>> Signal Handlers:
>>    SIGSEGV: [javaSignalHandler(int, siginfo_t*, void*)+0 in libjvm.so], sa_mask[0]=11100100010111111101111111111110, sa_flags=SA_RESTART|SA_SIGINFO
>>     SIGBUS: [javaSignalHandler(int, siginfo_t*, void*)+0 in libjvm.so], sa_mask[0]=11100100010111111101111111111110, sa_flags=SA_RESTART|SA_SIGINFO
>>     SIGFPE: [javaSignalHandler(int, siginfo_t*, void*)+0 in libjvm.so], sa_mask[0]=11100100010111111101111111111110, sa_flags=SA_RESTART|SA_SIGINFO
>>    SIGPIPE: [javaSignalHandler(int, siginfo_t*, void*)+0 in libjvm.so], sa_mask[0]=11100100010111111101111111111110, sa_flags=SA_RESTART|SA_SIGINFO
>>    SIGXFSZ: [javaSignalHandler(int, siginfo_t*, void*)+0 in libjvm.so], sa_mask[0]=11100100010111111101111111111110, sa_flags=SA_RESTART|SA_SIGINFO
>>     SIGILL: [javaSignalHandler(int, siginfo_t*, void*)+0 in libjvm.so], sa_mask[0]=11100100010111111101111111111110, sa_flags=SA_RESTART|SA_SIGINFO
>>    SIGUSR2: [SR_handler(int, siginfo_t*, ucontext*)+0 in libjvm.so], sa_mask[0]=00000000000000000000000000000000, sa_flags=SA_RESTART|SA_SIGINFO
>>     SIGHUP: [UserHandler(int, void*, void*)+0 in libjvm.so], sa_mask[0]=11100100010111111101111111111110, sa_flags=SA_RESTART|SA_SIGINFO
>>     SIGINT: [UserHandler(int, void*, void*)+0 in libjvm.so], sa_mask[0]=11100100010111111101111111111110, sa_flags=SA_RESTART|SA_SIGINFO
>>    SIGTERM: [UserHandler(int, void*, void*)+0 in libjvm.so], sa_mask[0]=11100100010111111101111111111110, sa_flags=SA_RESTART|SA_SIGINFO
>>    SIGQUIT: [UserHandler(int, void*, void*)+0 in libjvm.so], sa_mask[0]=11100100010111111101111111111110, sa_flags=SA_RESTART|SA_SIGINFO
>>    SIGTRAP: SIG_DFL, sa_mask[0]=00000000000000000000000000000000, sa_flags=none
>> 
>> The patch introduces a new function, `os::print_function_and_library_name`, which prints a combined function and library name. 
>> 
>> It also introduces gtests for that function. 
>> 
>> I plan to use it in other places to, and unify similar coding, e.g. when printing stack traces (NMT, VMError) or pointer locations (os::print_location). But I leave that for a future RFE.
>
> src/hotspot/os/posix/signals_posix.cpp line 1352:
> 
>> 1350:   LINUX_ONLY(sa.sa_flags &= SA_RESTORER_FLAG_MASK;)
>> 1351: 
>> 1352:   st->print("%10s: ", os::exception_name(sig, buf, buflen));
> 
> Where does the 10 come from? Why do we need to limit it?

> A minor comment, but otherwise this seems quite reasonable.
> 
> Thanks,
> David

Thanks, David!

`%10s` is not a limit, its for alignment. It makes all the signal names nicely aligned (all colons end up in the same column).

..Thomas

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PR: https://git.openjdk.java.net/jdk/pull/1839