[knem-devel] how to write INT value with KNEM "atomically"

Brice Goglin Brice.Goglin at inria.fr
Wed Sep 28 07:15:48 CEST 2011


Le 27/09/2011 23:05, George Bosilca a écrit :
> I mean a similar issue can happened to a normal read from a file. If
> the effective read is done on another thread that the one calling the
> syscall, just returning from the syscall doesn't means your process
> memory has been updated yet … The memory has to be flushed by the
> kernel before returning from a syscall…

I don't understand here. What do you call a flush? Cache-flush ?
Totally random example: Open-MX doesn't do anything to make
kernel-written data actually visible to user-space. It just adds a write
memory barrier to ensure that the notification flag is written at the
end. But there's no flush and even no return from syscall in most
receive cases.

Brice




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