Dear Experts,
I have code where I (1) use MAIN_THREAD_ASYNC_EM_ASM to
queue code to run on the main thread from a background
thread, and (2) protect some data structures from concurrent
access using pthread mutexes. I am compiling with -pthread.
I know that locking a mutex on the main thread involves
polling. My question is: can work that has been submitted by
MAIN_THREAD_ASYNC_EM_ASM run when this polling occurs?
It looks to me as if it does, which is surprising! But this is
hard to debug and I may have misinterpreted what is going
on.
I.e. (pseudo-code):
// Global:
int i; // Only access this on the main thread!
std::string s; // Only access this with mut locked!
std::mutex mut;
// Main thread, e.g. in WebGL drawing code, or an
// input event handler, etc:
i = 0;
mut.lock();
assert(i == 0); // Can this fail?
foo(s);
mut.unlock();
// Background (worker) thread:
void modify_i() { i++; }
MAIN_THREAD_ASYNC_EM_ASM({
Module.ccall('modify_i', null);
});
Thanks,
Phil.
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