Fix: hash table cleanup call_rcu deadlock

[lttng-tools.git] / src / bin / lttng-sessiond / utils.c

diff --git a/src/bin/lttng-sessiond/utils.c b/src/bin/lttng-sessiond/utils.c
index d503665a4fdb1149d68b00b79fcab14ed948bd4d..358e407e9c326cf038024b570f4c9209a724e2ca 100644 (file)
--- a/src/bin/lttng-sessiond/utils.c
+++ b/src/bin/lttng-sessiond/utils.c
@@ -23,6 +23,9 @@
 #include <common/error.h>
 
 #include "utils.h"
+#include "lttng-sessiond.h"
+
+int ht_cleanup_pipe[2] = { -1, -1 };
 
 /*
  * Write to writable pipe used to notify a thread.
@@ -31,6 +34,11 @@ int notify_thread_pipe(int wpipe)
 {
        int ret;
 
+       /* Ignore if the pipe is invalid. */
+       if (wpipe < 0) {
+               return 0;
+       }
+
        do {
                ret = write(wpipe, "!", 1);
        } while (ret < 0 && errno == EINTR);
@@ -50,3 +58,27 @@ const char *get_home_dir(void)
 {
        return ((const char *) getenv("HOME"));
 }
+
+void ht_cleanup_push(struct lttng_ht *ht)
+{
+       int ret;
+       int fd = ht_cleanup_pipe[1];
+
+       if (fd < 0)
+               return;
+       do {
+               ret = write(fd, &ht, sizeof(ht));
+       } while (ret < 0 && errno == EINTR);
+       if (ret < 0 || ret != sizeof(ht)) {
+               PERROR("write ht cleanup pipe %d", fd);
+               if (ret < 0) {
+                       ret = -errno;
+               }
+               goto error;
+       }
+
+       /* All good. Don't send back the write positive ret value. */
+       ret = 0;
+error:
+       assert(!ret);
+}