I ran: adb shell setprop debug.mono.env "-O=-intrins" Is this correct?
There was no difference in the outcome: When volatile keyword is used, errors occur. When Volatile class is used, no errors were spotted. Should I file a bug to the Runtime/JIT <https://bugzilla.xamarin.com/buglist.cgi?component=JIT&list_id=218467&product=Runtime&resolution=---> section? Where On Thu, Jul 7, 2016 at 11:32 AM, Alex Rønne Petersen <a...@alexrp.com> wrote: > Hi, > > By the way, I would suggest trying to run the app with something like: > > MONO_ENV_OPTIONS="-O=-intrins" > > For Android, see here how to set this: > https://developer.xamarin.com/guides/android/advanced_topics/environment/ > > For iOS, you'd need to set this when invoking the AOT compiler. I'm > not really familiar with where you'd need to do this, though. > > This would disable the JIT's intrinsics for the various atomics / > memory model methods in the framework. It would be good to know if > this makes the test case work or if the result is the same, as we > could narrow the problem down to either the JIT's intrinsics or the > fallback C code in the runtime. > > Regards, > Alex > > On Wed, Jul 6, 2016 at 5:13 PM, petrakeas <petrak...@gmail.com> wrote: > > According to C# specification > > <https://msdn.microsoft.com/en-us/library/ms228593.aspx> : > > > > • A read of a volatile field is called a volatile read. A volatile > read has > > “acquire semantics”; that is, it is guaranteed to occur prior to any > > references to memory that occur after it in the instruction sequence. > > • A write of a volatile field is called a volatile write. A > volatile write > > has “release semantics”; that is, it is guaranteed to happen after any > > memory references prior to the write instruction in the instruction > > sequence. > > > > The spec presents an example > > <https://msdn.microsoft.com/en-us/library/aa645755(v=vs.71).aspx> > where > > one thread writes "data" on a non volatile variable and "publishes" the > > result by writing on a volatile variable that acts as a flag. The other > > thread checks the volatile flag and if set, it accesses the non-volatile > > variable that is now *guaranteed* to contain the data. > > > > It seems that Mono 4.4 (the one used in Xamarin) does not enforce these > > semantics or in other words does not prevent memory re-ordering in > Android > > and iOS that have relaxed memory models due to their CPU. > > > > I have created an a test that reproduces the problem in iOS and Android > > Program.cs <http://mono.1490590.n4.nabble.com/file/n4668111/Program.cs> > . > > > > If the access to the volatile field is replaced by Volatile.Read() and > > Volatile.Write(), then no-problems occur. It seems that Volatile.Read() > and > > Volatile.Write() implement half fences in Mono, but the volatile keyword > > does not. > > > > Is this a bug? > > > > > > > > > > -- > > View this message in context: > http://mono.1490590.n4.nabble.com/Volatile-fields-don-t-enforce-acquire-release-semantics-like-Volatile-Read-and-Volatile-Write-tp4668111.html > > Sent from the Mono - Dev mailing list archive at Nabble.com. > > _______________________________________________ > > Mono-devel-list mailing list > > Mono-devel-list@lists.ximian.com > > http://lists.ximian.com/mailman/listinfo/mono-devel-list > -- Petros Douvantzis Co-founder Horizon Video Technologies horizon.camera
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