On Fri, 01 Jul 2011 01:14:26 -0400, Andrej Mitrovic
<andrej.mitrov...@gmail.com> wrote:
I have two functions running concurrently and they share data via a
globally shared array.
Generally one thread modifies an array and potentially changes its
length, the other thread reads from it. I have to avoid too many locks
and message passing wouldn't really work since I need fast access to
the array.
I can't use the array directly in the reading thread because the array
could possibly be reallocated by the writing thread (e.g. if it
changes the .length property), while at the same time the reading
thread could just have sent the .ptr value of that array to some API
function. I've had this problem occur and the app would crash due to a
reallocation while the API was reading the array.
Here's the gist of it:
__gshared int[] values;
void foo()
{
// modify, write to the array, and possibly change the length
}
It's not quite safe (even with locks) to alter __gshared array lengths
from more than one thread. This is due to the assumption that any array
not marked shared is thread local. This includes __gshared data, since
__gshared is not part of the type.
What can happen is the array block information can be cached in the thread
local LRU append cache, and another thread could extend the data, thereby
changing the block information. When the first thread then tries to use
the block information, he gets a stale block info from the runtime, and
can make incorrect assumptions.
Have you tried changing __gshared to shared? shared should be supported.
-Steve
