Re: [libvirt PATCH 03/11] src: set the OS level thread name

22 Feb 2020

On 2/14/20 1:52 PM, Daniel P. Berrangé wrote:
...
Setting the thread name makes it easier to debug libvirtd
when many threads are running.
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
  src/libvirt_private.syms |  1 +
  src/util/virthread.c     | 44 +++++++++++++++++++++++++++++++++++-----
  src/util/virthread.h     |  4 +++-
  3 files changed, 43 insertions(+), 6 deletions(-)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index dc0449d1d8..375e6ea000 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -3258,6 +3258,7 @@ virThreadCreateFull;
  virThreadID;
  virThreadIsSelf;
  virThreadJoin;
+virThreadMaxName;
  virThreadSelf;
  virThreadSelfID;
diff --git a/src/util/virthread.c b/src/util/virthread.c
index cdc5cab604..750e8d5655 100644
--- a/src/util/virthread.c
+++ b/src/util/virthread.c
@@ -175,23 +175,57 @@ void virCondBroadcast(virCondPtr c)
struct virThreadArgs {
      virThreadFunc func;
-    const char *funcName;
+    char *name;
      bool worker;
      void *opaque;
  };
+size_t virThreadMaxName(void)
+{
+#if defined(__FreeBSD__) || defined(__APPLE__)
+    return 63;
+#else
+# ifdef __linux__
+    return 15;
+# else
+    return 0; /* unlimited */
+# endif
+#endif
+}
It's a pitty that the 16 bytes long limit wasn't lifted since 2.6.12-rc2.
...
+
  static void *virThreadHelper(void *data)
  {
      struct virThreadArgs *args = data;
      struct virThreadArgs local = *args;
+    g_autofree char *thname = NULL;
+    size_t maxname = virThreadMaxName();
/* Free args early, rather than tying it up during the entire thread.  */
      VIR_FREE(args);
if (local.worker)
-        virThreadJobSetWorker(local.funcName);
+        virThreadJobSetWorker(local.name);
      else
-        virThreadJobSet(local.funcName);
+        virThreadJobSet(local.name);
+
+    if (maxname) {
+        thname = g_strndup(local.name, maxname);
+    } else {
+        thname = g_strdup(local.name);
+    }
+    g_free(local.name);
+
+#if defined(__linux__) || defined(WIN32)
+    pthread_setname_np(pthread_self(), thname);
+#else
+# ifdef __FreeBSD__
+    pthread_set_name_np(pthread_self(), thname);
+# else
+#  ifdef __APPLE__
+    pthread_setname_np(thname);
+#  endif
+# endif
+#endif
local.func(local.opaque);
@@ -204,7 +238,7 @@ static void *virThreadHelper(void *data)
  int virThreadCreateFull(virThreadPtr thread,
                          bool joinable,
                          virThreadFunc func,
-                        const char *funcName,
+                        const char *name,
                          bool worker,
                          void *opaque)
  {
@@ -221,7 +255,7 @@ int virThreadCreateFull(virThreadPtr thread,
      }
args->func = func;
-    args->funcName = funcName;
+    args->name = g_strdup(name);
      args->worker = worker;
      args->opaque = opaque;
Don't forget to free args->name if pthread_create() fails.

Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

Michal

    