signal-util: add common implementation for propagating a signal

i.e. let's add a common logic to be called from a signal handler to
raise the passed signal again.

Follow-up for: #25399

1 files changed, 18 insertions, 0 deletions

diff --git a/src/basic/signal-util.c b/src/basic/signal-util.c
index b61c18b2de..7875ca69bb 100644
--- a/src/basic/signal-util.c
+++ b/src/basic/signal-util.c
@@ -5,6 +5,7 @@
 
 #include "errno-util.h"
 #include "macro.h"
+#include "missing_syscall.h"
 #include "parse-util.h"
 #include "signal-util.h"
 #include "stdio-util.h"
@@ -282,3 +283,20 @@ int pop_pending_signal_internal(int sig, ...) {
 
         return r; /* Returns the signal popped */
 }
+
+void propagate_signal(int sig, siginfo_t *siginfo) {
+        pid_t p;
+
+        /* To be called from a signal handler. Will raise the same signal again, in our process + in our threads.
+         *
+         * Note that we use raw_getpid() instead of getpid_cached(). We might have forked with raw_clone()
+         * earlier (see PID 1), and hence let's go to the raw syscall here. In particular as this is not
+         * performance sensitive code.
+         *
+         * Note that we use kill() rather than raise() as fallback, for similar reasons. */
+
+        p = raw_getpid();
+
+        if (rt_tgsigqueueinfo(p, gettid(), sig, siginfo) < 0)
+                assert_se(kill(p, sig) >= 0);
+}