Ah, indeed, so a workaround would be:
my $lock = Lock.new;
my $set = SetHash.new;
await ^16 .map: {
start {
for ^10000 {
$lock.protect: { $set<1> = True; 1 }
$lock.protect: { $set<1> = False; 1 }
}
}
}
So maybe a solution would be to test for Proxy of the return value of the
block, and then sink it?
> On 14 Nov 2017, at 16:59, Timo Paulssen via RT <[email protected]>
> wrote:
>
> I already figured out that it's about sinking the result of assigning to
> the SetHash. When you access it you get a proxy, that is the return
> value of the lock-protected block, and the proxy gets sunk outside of
> it, thus causing concurrent access to the SetHash.
>
>
> On 14/11/17 16:03, Elizabeth Mattijsen wrote:
>> reducing the code to:
>>
>> use nqp;
>> my $lock = Lock.new;
>> my $hash := nqp::hash;
>> await ^16 .map: {
>> start {
>> for ^1000 {
>> $lock.protect: { nqp::bindkey($hash,"a",1) }
>> $lock.protect: { nqp::deletekey($hash,"a") }
>> }
>> }
>> }
>>
>> does *not* make it crash. So it would appear that it’s not the lowlevel
>> hash access that’s to blame. Looking at this with Telemetry.snapper, this
>> *does* seem to eat a lot of memory very quickly. With a slightly bigger
>> version, and much longer running, growth to about 490MB is observed
>> (starting from 69MB) in 35 seconds, then remaining constant for about 125
>> seconds, after which a modest increase of only about 15KB per second was
>> observed for the remainder of the run.
>>
>> So the next maybe it’s something in handling Proxy.
>>
>>
>>> On 10 Nov 2017, at 03:28, David Lowe <[email protected]> wrote:
>>>
>>> This crash still occurs with rakudo 2017.10.
>>>
>>> On Thu, Oct 5, 2017 at 9:10 PM, perl6 via RT <[email protected]>
>>> wrote:
>>> Greetings,
>>>
>>> This message has been automatically generated in response to the
>>> creation of a trouble ticket regarding:
>>> "segmentation fault while concurrently updating SetHash",
>>> a summary of which appears below.
>>>
>>> There is no need to reply to this message right now. Your ticket has been
>>> assigned an ID of [perl #132225].
>>>
>>> Please include the string:
>>>
>>> [perl #132225]
>>>
>>> in the subject line of all future correspondence about this issue. To do so,
>>> you may reply to this message.
>>>
>>> Thank you,
>>> [email protected]
>>>
>>> -------------------------------------------------------------------------
>>> This short program crashes reliably (with a segmentation fault) on my
>>> system:
>>>
>>> ```
>>> #!/usr/bin/env perl6
>>>
>>> use v6.c;
>>>
>>> my $lock = Lock.new;
>>> my $set = SetHash.new;
>>> await (^12).map: {
>>> start {
>>> for (^1000) {
>>> $lock.protect: { $set<1> = True }
>>> $lock.protect: { $set<1> = False }
>>> }
>>> }
>>> }
>>> ```
>>>
>>> More information:
>>>
>>> ```
>>> $ perl6 --version
>>> This is Rakudo version 2017.09 built on MoarVM version 2017.09.1
>>> implementing Perl 6.c.
>>> ```
>>>
>>>
