RFR (S): 8237775: Core file generation will silently fail if /cores directory has wrong permissions set

[Yasumasa Suenaga]

Hi Gerard,

os_posix.cpp:

   I think we should not create any file in have_file_write_permission() because it might remain without being removed.
   Can you check the permission of parent directory?


Thanks,

Yasumasa


On 2020/05/19 5:06, gerard ziemski wrote:
> hi all,
> 
> Please review this enhancement, which adds explanation to the user when we can not dump core file (i.e. "The core files directory does not exist or it has no write permissions.") because either the core folder does not exist or the process has no write permission in that folder (i.e. default behavior on recent macOS). We already warn the users when "ulimit" is not set, so we are just trying to be consistent and cover all cases that can cause the core dump not to happen.
> 
> Even though we are adding more code to the signal handler here, it shouldn't affect it negatively. I couldn't measure (using Xcode profiler) any memory impact of the new code (i.e. fopen/close/remove APIs) Moreover we already use "fopen()" and "fclose()" when writing the hs_err log, so the only new API used is "remove()".
> 
> We could conceivably move this code to the startup and cache the answer to be later used in signal handler (it does impact the the startup by -0.6% for "hello world" test case), but I don't like the idea of adding more code to the startup, when it's not going to be used majority of the time.
> 
> Please notice that I had to move the "Default location:" part of the message around, so that it gets printed after the new "The core files directory does not exist or it has no write permissions." message. That's because some tests expect the core location immediately after "Default location:".
> 
> 
> Before this change a usual message would look like this:
> 
> # No core dump will be written. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
> 
> or
> 
> # Core dump will be written. Default location: /cores/core.8201
> 
> 
> Now we can print:
> 
> # No core dump will be written. The core files directory does not exist or it has no write permissions. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
> 
> or
> 
> # Core dump will be requested from the system. The core files directory does not exist or it has no write permissions. Default location: /cores/core.8171
> 
> 
> bug: https://bugs.openjdk.java.net/browse/JDK-8237775
> webrev: http://cr.openjdk.java.net/~gziemski/8237775_rev1
> testing: passes Mach5 hs-tier1,2,3,4,5
> 
> 
> cheers