Hi, Please file it for the Mono runtime, rather, as the vast majority of our memory model related code lives in the runtime/JIT.
Regards, Alex On Thu, Jul 7, 2016 at 10:27 AM, Petros Douvantzis <petrak...@gmail.com> wrote: > Hi, > > I will file a bug. > > I think that I should file one bug int the iOS BCL libraries and one for the > Android BCL, right? I guess the solution will be related to one another > though. > > Best, > > On Thu, Jul 7, 2016 at 11:20 AM, Alex Rønne Petersen <a...@alexrp.com> > wrote: >> >> Hi, >> >> It is correct that the volatile keyword should result in >> acquire/release barriers as a result of compiling down to >> Thread.VolatileRead () / VolatileWrite () calls. In theory, the only >> difference between the Thread and Volatile methods is that the >> Volatile methods will actually be atomic for 64-bit quantities on a >> 32-bit machine, where the Thread methods will not (incidentally, this >> is why the volatile keyword is not allowed on 64-bit types). But since >> you're using a 32-bit value, this shouldn't matter. So the fact that >> switching the code to the Volatile methods makes it work is very >> strange indeed. >> >> Could you file a bug with the test case you provided? >> >> 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 > > _______________________________________________ Mono-devel-list mailing list Mono-devel-list@lists.ximian.com http://lists.ximian.com/mailman/listinfo/mono-devel-list
