LibC: Simplify the gettid() cache by just clearing the cache in fork()

It's hilarious how much better this is.

Thanks to Sergey for suggesting it! :^)

1 files changed, 7 insertions, 19 deletions

diff --git a/Libraries/LibC/unistd.cpp b/Libraries/LibC/unistd.cpp
index 679817a937..d1891c146a 100644
--- a/Libraries/LibC/unistd.cpp
+++ b/Libraries/LibC/unistd.cpp
@@ -46,6 +46,8 @@
 
 extern "C" {
 
+static __thread int s_cached_tid = 0;
+
 int chown(const char* pathname, uid_t uid, gid_t gid)
 {
     if (!pathname) {
@@ -66,6 +68,8 @@ int fchown(int fd, uid_t uid, gid_t gid)
 pid_t fork()
 {
     int rc = syscall(SC_fork);
+    if (rc == 0)
+        s_cached_tid = 0;
     __RETURN_WITH_ERRNO(rc, rc, -1);
 }
 
@@ -548,27 +552,11 @@ int ftruncate(int fd, off_t length)
     __RETURN_WITH_ERRNO(rc, rc, -1);
 }
 
-struct ThreadInfoCache {
-    int tid { 0 };
-};
-
-__thread ThreadInfoCache* thread_info_cache;
-
 int gettid()
 {
-    if (!thread_info_cache) {
-        thread_info_cache = (ThreadInfoCache*)mmap(nullptr, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
-        ASSERT(thread_info_cache != MAP_FAILED);
-        if (minherit(thread_info_cache, PAGE_SIZE, MAP_INHERIT_ZERO) < 0) {
-            perror("minherit(MAP_INHERIT_ZERO)");
-            ASSERT_NOT_REACHED();
-        }
-    }
-
-    if (thread_info_cache->tid == 0)
-        thread_info_cache->tid = syscall(SC_gettid);
-
-    return thread_info_cache->tid;
+    if (!s_cached_tid)
+        s_cached_tid = syscall(SC_gettid);
+    return s_cached_tid;
 }
 
 int donate(int tid)