RFR 8027434: "-XX:OnOutOfMemoryError" uses fork instead of vfork

[Muthusamy Chinnathambi]

Hi David,

Sorry for the delayed response.
Please find the updated webrev at http://cr.openjdk.java.net/~mchinnathamb/8027434/webrev.03/ 
Tested with mach5 hs-tier1-4

Regards,
Muthusamy C


-----Original Message-----
From: David Holmes 
Sent: Thursday, September 27, 2018 6:52 PM
To: Muthusamy Chinnathambi <muthusamy.chinnathambi at oracle.com>; hotspot-runtime-dev at openjdk.java.net
Subject: Re: RFR 8027434: "-XX:OnOutOfMemoryError" uses fork instead of vfork

Hi,

On 27/09/2018 8:18 AM, Muthusamy Chinnathambi wrote:
> Hi David,
> 
>> That doesn't work.
> I get your point. My bad.
> 
>> Only the caller knows why it is being called.
> Please find the updated webrev at http://cr.openjdk.java.net/~mchinnathamb/8027434/webrev.02/
> This now uses a static helper to decide.

Sorry but I really don't like this version using is_forkmode_vfork. It's 
awkward to introduce a Linux specific feature into a shared API. But I 
think the best way to do this would be to introduce a new default 
parameter to os::fork_and_exec

static int fork_and_exec(char *cmd, bool use_vfork_if_available = false);

then the impl in o_linux.cpp which use the arg to select fork or vfork. 
And vmError will do:

if (os::fork_and_exec(cmd, true) < 0) {

Thanks,
David

> Regards,
> Muthusamy C
> 
> -----Original Message-----
> From: David Holmes
> Sent: Friday, September 21, 2018 7:27 PM
> To: Muthusamy Chinnathambi <muthusamy.chinnathambi at oracle.com>; hotspot-runtime-dev at openjdk.java.net
> Subject: Re: RFR 8027434: "-XX:OnOutOfMemoryError" uses fork instead of vfork
> 
> Sorry for the delay.
> 
> On 19/09/2018 7:48 AM, Muthusamy Chinnathambi wrote:
>> Hi David,
>>
>> Please find the updated webrev at http://cr.openjdk.java.net/~mchinnathamb/8027434/webrev.01/
>> Instead of creating a static helper, I have moved the decision to the fork_and_exec routine itself.
> 
> That doesn't work. Just because we have an OnOutOfMemoryError handler
> set it doesn't mean the call to os::fork_and_exec was made to run that
> handler. Only the caller knows why it is being called.
> 
> David
> 
>> Tested with mach5 hs-tier1-4.
>>
>> Regards,
>> Muthusamy C
>>
>> -----Original Message-----
>> From: Muthusamy Chinnathambi
>> Sent: Friday, September 14, 2018 12:03 PM
>> To: David Holmes <david.holmes at oracle.com>; hotspot-runtime-dev at openjdk.java.net
>> Subject: RE: RFR 8027434: "-XX:OnOutOfMemoryError" uses fork instead of vfork
>>
>> Hi David,
>>
>>> please refactor into a static helper function
>> Sure, I will change and get back after testing.
>>
>> Regards,
>> Muthusamy C
>>
>> -----Original Message-----
>> From: David Holmes
>> Sent: Friday, September 14, 2018 11:16 AM
>> To: Muthusamy Chinnathambi <muthusamy.chinnathambi at oracle.com>; hotspot-runtime-dev at openjdk.java.net
>> Subject: Re: RFR 8027434: "-XX:OnOutOfMemoryError" uses fork instead of vfork
>>
>> Hi Muthusamy,
>>
>> Instead of duplicating all the code - which I think only differs in the
>> fork versus vfork line - please refactor into a static helper function
>> that takes a boolean vfork and call that from
>> fork_and_exec/vfork_and_exec selecting fork or vfork as appropriate.
>>
>> I'm still mulling over whether there is a cleaner way to do this other
>> than introducing a linux only entry to the os class.
>>
>> Thanks,
>> David
>>
>>
>> On 14/09/2018 1:55 PM, Muthusamy Chinnathambi wrote:
>>> Hi all,
>>>
>>> Could you review this fix for JDK-8027434 - to use vfork instead of fork for -XX:OnOutOfMemoryError.
>>>
>>> See bug comments for more details.
>>>
>>> Bug URL: https://bugs.openjdk.java.net/browse/JDK-8027434
>>> Webrev URL: http://cr.openjdk.java.net/~mchinnathamb/8027434/webrev.00/
>>>
>>> Tested with mach5 hs-tier1-4.
>>>
>>> Regards,
>>> Muthusamy C
>>>