osdep: Introduce qemu_kill_thread()

Add a function for sending signals to individual threads. It does not make
sense on Windows, so do not provide an implementation, so that if someone
uses it by accident, they will get a linker error.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Warner Losh <imp@bsdimp.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Message-Id: <20250117001542.8290-6-iii@linux.ibm.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20250207153112.3939799-15-alex.bennee@linaro.org>

include/qemu/osdep.h

@@ -631,6 +631,15 @@ bool qemu_write_pidfile(const char *pidfile, Error **errp);
 
 int qemu_get_thread_id(void);
 
+/**
+ * qemu_kill_thread:
+ * @tid: thread id.
+ * @sig: host signal.
+ *
+ * Send @sig to one of QEMU's own threads with identifier @tid.
+ */
+int qemu_kill_thread(int tid, int sig);
+
 #ifndef CONFIG_IOVEC
 struct iovec {
     void *iov_base;

util/oslib-posix.c

@@ -111,6 +111,21 @@ int qemu_get_thread_id(void)
 #endif
 }
 
+int qemu_kill_thread(int tid, int sig)
+{
+#if defined(__linux__)
+    return syscall(__NR_tgkill, getpid(), tid, sig);
+#elif defined(__FreeBSD__)
+    return thr_kill2(getpid(), tid, sig);
+#elif defined(__NetBSD__)
+    return _lwp_kill(tid, sig);
+#elif defined(__OpenBSD__)
+    return thrkill(tid, sig, NULL);
+#else
+    return kill(tid, sig);
+#endif
+}
+
 int qemu_daemon(int nochdir, int noclose)
 {
     return daemon(nochdir, noclose);