diff options
Diffstat (limited to 'Utilities/cmlibuv/src/unix/async.c')
| -rw-r--r-- | Utilities/cmlibuv/src/unix/async.c | 33 |
1 files changed, 23 insertions, 10 deletions
diff --git a/Utilities/cmlibuv/src/unix/async.c b/Utilities/cmlibuv/src/unix/async.c index 26d337e..5f58fb8 100644 --- a/Utilities/cmlibuv/src/unix/async.c +++ b/Utilities/cmlibuv/src/unix/async.c @@ -32,6 +32,7 @@ #include <stdlib.h> #include <string.h> #include <unistd.h> +#include <sched.h> /* sched_yield() */ #ifdef __linux__ #include <sys/eventfd.h> @@ -81,20 +82,32 @@ int uv_async_send(uv_async_t* handle) { /* Only call this from the event loop thread. */ static int uv__async_spin(uv_async_t* handle) { + int i; int rc; for (;;) { - /* rc=0 -- handle is not pending. - * rc=1 -- handle is pending, other thread is still working with it. - * rc=2 -- handle is pending, other thread is done. + /* 997 is not completely chosen at random. It's a prime number, acyclical + * by nature, and should therefore hopefully dampen sympathetic resonance. */ - rc = cmpxchgi(&handle->pending, 2, 0); - - if (rc != 1) - return rc; - - /* Other thread is busy with this handle, spin until it's done. */ - cpu_relax(); + for (i = 0; i < 997; i++) { + /* rc=0 -- handle is not pending. + * rc=1 -- handle is pending, other thread is still working with it. + * rc=2 -- handle is pending, other thread is done. + */ + rc = cmpxchgi(&handle->pending, 2, 0); + + if (rc != 1) + return rc; + + /* Other thread is busy with this handle, spin until it's done. */ + cpu_relax(); + } + + /* Yield the CPU. We may have preempted the other thread while it's + * inside the critical section and if it's running on the same CPU + * as us, we'll just burn CPU cycles until the end of our time slice. + */ + sched_yield(); } } |