The ARM platform does not do atomic operations. That's a limitation of the architecture, not the compiler.
Read this, it's an interesting discussion on the issue with some suggestions: http://stackoverflow.com/questions/11894059/atomic-operations-in-arm On Apr 8, 2015 4:41 AM, "Alexey Perevalov" <alexey.pereva...@hotmail.com> wrote: > Hello community, > > I faced with bug in multithread environment in objective C code which > using dispatch_async and block, > __sync_add_and_fetch increments global variable. But in case of many..many > threads> 5, after every > __sync_add_and_fetch got damaged > > > ... > int32_t count = 0; > > ... > > int > main(int argc, char *argv[]) > { > for (i = 1; i < 32; ++i) { > ... > char* name; > asprintf(&name, "test.overcommit.%d", i); > > dispatch_queue_t queue = dispatch_queue_create(name, NULL); > free(name); > dispatch_set_target_queue(queue, dispatch_get_global_queue(0, > dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_LOW, > 0))); > > /* async queue */ > dispatch_async(queue, ^{ > __sync_add_and_fetch(&count, 1); //<< Here count is corrupted > in case of number of threads> ~5 > printf("count addr %p, value %d\n", &count, count); > fflush(stdout); > }); > > } > ... > dispatch_main(); > } > > in case of count is local variable in scope of main function and has > __block attribute, all is fine. > > I'm using > clang version 3.3 (tags/RELEASE_33/final) > Target: armv7l-unknown-linux-gnueabi > Thread model: posix > libBlockRuntime 0.3 > libdispatch for linux 1.2 > CPU is ARMv7, > in disas I see dmb ish instruction, but I don't know is it enough. > > I understand, my clang is out of date. Moving to new version could be > painful ) > Maybe somebody knows, was that bug fixed? > > BR, > Alexey > > _______________________________________________ > Gnustep-dev mailing list > Gnustep-dev@gnu.org > https://lists.gnu.org/mailman/listinfo/gnustep-dev >
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