Call pthread_attr_init in jl_init_stack_limits

[ararslan]

#55515 seems to have introduced segfaults on FreeBSD during the atexit and ccall tests. Prior to that PR, we had been calling pthread_attr_init in jl_init_stack_limits on FreeBSD. According to the manual page for pthread_attr_get_np, it is "HIGHLY RECOMMENDED" to use pthread_attr_init to allocate storage. Might as well put it back then, and hopefully it'll fix the segfaults.

[ararslan]

Looks like this indeed fixes the atexit segfaults on FreeBSD. The CI failures for the build on musl Linux and tests for Linux PowerPC, AArch64, and x86_64 with assertions are unrelated.

[vtjnash]

This should be in the FreeBSD only section?

[ararslan]

I don't know, should it? Doesn't seem to be required on Linux though it shouldn't hurt to call it.

[vtjnash]

It may cause a memory leak, since it fails to get destroyed

[ararslan]

Doesn't it get destroyed here?

julia/src/init.c

Line 78 in 7d2a7de

pthread_attr_destroy(&attr);

[vtjnash]

The second does, but not the first

[ararslan]

I don't understand, I only see one pthread_attr_t being created in this function, line 68:

julia/src/init.c

Lines 50 to 101 in 7d2a7de

	void jl_init_stack_limits(int ismaster, void **stack_lo, void **stack_hi)
	{
	#ifdef _OS_WINDOWS_
	(void)ismaster;
	// https://en.wikipedia.org/wiki/Win32_Thread_Information_Block
	# ifdef _P64
	*stack_hi = (void**)__readgsqword(0x08); // Stack Base / Bottom of stack (high address)
	*stack_lo = (void**)__readgsqword(0x10); // Stack Limit / Ceiling of stack (low address)
	# else // !_P64
	*stack_hi = (void**)__readfsdword(0x04); // Stack Base / Bottom of stack (high address)
	*stack_lo = (void**)__readfsdword(0x08); // Stack Limit / Ceiling of stack (low address)
	# endif // _P64
	#else // !_OS_WINDOWS_
	// Only use pthread_*_np functions to get stack address for non-master
	// threads since it seems to return bogus values for master thread on Linux
	// and possibly OSX.
	if (!ismaster) {
	# if defined(_OS_LINUX_) || defined(_OS_FREEBSD_)
	pthread_attr_t attr;
	pthread_attr_init(&attr);
	#if defined(_OS_FREEBSD_)
	pthread_attr_get_np(pthread_self(), &attr);
	#else
	pthread_getattr_np(pthread_self(), &attr);
	#endif
	void *stackaddr;
	size_t stacksize;
	pthread_attr_getstack(&attr, &stackaddr, &stacksize);
	pthread_attr_destroy(&attr);
	*stack_lo = stackaddr;
	*stack_hi = (char*)stackaddr + stacksize;
	return;
	# elif defined(_OS_DARWIN_)
	extern void *pthread_get_stackaddr_np(pthread_t thread);
	extern size_t pthread_get_stacksize_np(pthread_t thread);
	pthread_t thread = pthread_self();
	void *stackaddr = pthread_get_stackaddr_np(thread);
	size_t stacksize = pthread_get_stacksize_np(thread);
	*stack_lo = (char*)stackaddr - stacksize;
	*stack_hi = stackaddr;
	return;
	# else
	# warning "Getting precise stack size for thread is not supported."
	# endif
	}
	struct rlimit rl;
	getrlimit(RLIMIT_STACK, &rl);
	size_t stacksize = rl.rlim_cur;
	*stack_hi = __builtin_frame_address(0);
	*stack_lo = (void*)((char*)*stack_hi - stacksize);
	#endif
	}

[ararslan]

I still don't get why it shouldn't be called on Linux, but at any rate, I've moved the call to be FreeBSD only.

[ararslan]

Quoth Jameson in Slack, "just merge." Okie dokie