From: Guillaume Solignac <gsoligna@cisco.com>
Date: Wed, 22 May 2024 08:47:33 +0000 (+0200)
Subject: vlib: prevent some signals from being executed on workers
X-Git-Tag: v25.02-rc0~242
X-Git-Url: https://gerrit.fd.io/r/gitweb?a=commitdiff_plain;h=5444973bd08ff8e9a103fb3436adbdcbb2f666b8;p=vpp.git

vlib: prevent some signals from being executed on workers

Before this commit, SIGINT, SIGHUP and SIGTERM could be executed on the
workers. Since those signals don't stop execution, it meant that atexit
handlers (like the `vl_unmap_shmem`) could run while the main thread was
still running, which can cause race conditions. To avoid that, we
prevent workers from handling those signals.

Type: fix
Signed-off-by: Guillaume Solignac <gsoligna@cisco.com>
Change-Id: I27a87d96a027d7423ced881a614427af4ab0f969
---

diff --git a/src/vlib/threads.c b/src/vlib/threads.c
index 87b71adc2bc..854d69448ac 100644
--- a/src/vlib/threads.c
+++ b/src/vlib/threads.c
@@ -370,6 +370,8 @@ void
 vlib_worker_thread_init (vlib_worker_thread_t * w)
 {
   vlib_thread_main_t *tm = vlib_get_thread_main ();
+  sigset_t signals;
+  int rv;
 
   /*
    * Note: disabling signals in worker threads as follows
@@ -379,7 +381,17 @@ vlib_worker_thread_init (vlib_worker_thread_t * w)
    *    sigfillset (&s);
    *    pthread_sigmask (SIG_SETMASK, &s, 0);
    *  }
+   * We can still disable signals for SIGINT,SIGHUP and SIGTERM as they don't
+   * trigger post-dump handlers anyway.
    */
+  sigemptyset (&signals);
+  sigaddset (&signals, SIGINT);
+  sigaddset (&signals, SIGHUP);
+  sigaddset (&signals, SIGTERM);
+  rv = pthread_sigmask (SIG_BLOCK, &signals, NULL);
+
+  if (rv)
+    clib_warning ("Failed to set the worker signal mask");
 
   clib_mem_set_heap (w->thread_mheap);