FreeBSD: Improve CPU core count handling

This improves the CPU core count handling for FreeBSD. This uses sysconf
to grab the number of configured processors when logical and physical
CPU counts are requested, and then pthread_getaffinity_np and the number
of active processors. This takes into account the number of available
cores when the process is restricted to a subset of the processors.

This also fixes the `dispatch_workqueye` test, which has its own
implementation to extract the core count. FreeBSD does not have an
`hw.activecpu` syscall, so the syscallbyname was failing and the
activecpu count was garbage from the stack. I've updated the test to
initialize the value with `0xa1a1a1` to make the garbage clearer.
Also update the test for FreeBSD to take advantage of sysconf and
pthread_getaffinity_np in the test.

Fixes: #897

Author: etcwilde

src/shims.h

@@ -58,9 +58,6 @@
 #define DISPATCH_WORKQ_MAX_PTHREAD_COUNT 255
 #endif
 
-#include "shims/hw_config.h"
-#include "shims/priority.h"
-
 #if HAVE_PTHREAD_NP_H
 #include <pthread_np.h>
 #endif
@@ -69,6 +66,9 @@
 #include <pthread/private.h>
 #endif
 
+#include "shims/hw_config.h"
+#include "shims/priority.h"
+
 #if !HAVE_DECL_FD_COPY
 #define FD_COPY(f, t) (void)(*(t) = *(f))
 #endif

src/shims/hw_config.h

@@ -102,14 +102,14 @@ static inline uint32_t
 _dispatch_hw_get_config(_dispatch_hw_config_t c)
 {
 	uint32_t val = 1;
-#if defined(__linux__) && HAVE_SYSCONF
+#if defined(__FreeBSD__) || (defined(__linux__) && HAVE_SYSCONF)
 	switch (c) {
 	case _dispatch_hw_config_logical_cpus:
 	case _dispatch_hw_config_physical_cpus:
 		return (uint32_t)sysconf(_SC_NPROCESSORS_CONF);
 	case _dispatch_hw_config_active_cpus:
 		{
-#ifdef __USE_GNU
+#if defined(__FreeBSD__) || __USE_GNU
 			// Prefer pthread_getaffinity_np because it considers
 			// scheduler cpu affinity.  This matters if the program
 			// is restricted to a subset of the online cpus (eg via numactl).

tests/dispatch_workqueue.c

@@ -4,6 +4,10 @@
 #if defined(__linux__)
 // For pthread_getaffinity_np()
 #include <pthread.h>
+#elif defined(__FreeBSD__)
+// for pthread_getaffinity_np / cpu_set_t
+#include <pthread.h>
+#include <pthread_np.h>
 #endif
 
 struct test_context {
@@ -37,11 +41,11 @@ spin(void *context)
 static uint32_t
 activecpu(void)
 {
-        uint32_t activecpu;
-#if defined(__linux__) || defined(__OpenBSD__)
+        uint32_t activecpu = 0xa1a1a1;
+#if defined(__linux__) || defined(__OpenBSD__) || defined(__FreeBSD__)
         activecpu = (uint32_t)sysconf(_SC_NPROCESSORS_ONLN);
 
-#if defined(__linux__) && __USE_GNU
+#if defined(__FreeBSD__) || (defined(__linux__) && __USE_GNU)
         cpu_set_t cpuset;
         if (pthread_getaffinity_np(pthread_self(),
                                    sizeof(cpu_set_t),