vlmemory/svm: fix client detach from svm region

Clients cannot know at svm region detach time if the shm backing files
have been recreated (e.g., if vpp restarts) and therefore should not try
to unlink them. Otherwise, terminating clients attached to previous
instantiations of a re-allocated region end up making the new instance
un-mappable by removing its backing file.

Change-Id: Idcd0cab776e63fd75b821bc9f0fac58217b9ccbe
Signed-off-by: Florin Coras <fcoras@cisco.com>

2 files changed, 36 insertions, 5 deletions

diff --git a/src/svm/svm.c b/src/svm/svm.c
index d3e56c1a46a..16a58fa126a 100644
--- a/src/svm/svm.c
+++ b/src/svm/svm.c
@@ -1034,7 +1034,7 @@ svm_region_unlink (svm_region_t * rp)
  * a new region client showing up at the wrong moment.
  */
 void
-svm_region_unmap (void *rp_arg)
+svm_region_unmap_internal (void *rp_arg, u8 is_client)
 {
   int i, mypid = getpid ();
   int nclients_left;
@@ -1134,7 +1134,12 @@ found:
       vec_free (name);
 
       region_unlock (rp);
-      svm_region_unlink (rp);
+
+      /* If a client asks for the cleanup, don't unlink the backing
+       * file since we can't tell if it has been recreated. */
+      if (!is_client)
+	svm_region_unlink (rp);
+
       munmap ((void *) virtual_base, virtual_size);
       region_unlock (root_rp);
       svm_pop_heap (oldheap);
@@ -1147,11 +1152,23 @@ found:
   munmap ((void *) virtual_base, virtual_size);
 }
 
+void
+svm_region_unmap (void *rp_arg)
+{
+  svm_region_unmap_internal (rp_arg, 0 /* is_client */ );
+}
+
+void
+svm_region_unmap_client (void *rp_arg)
+{
+  svm_region_unmap_internal (rp_arg, 1 /* is_client */ );
+}
+
 /*
  * svm_region_exit
  */
-void
-svm_region_exit ()
+static void
+svm_region_exit_internal (u8 is_client)
 {
   void *oldheap;
   int i, mypid = getpid ();
@@ -1191,7 +1208,7 @@ svm_region_exit ()
 
 found:
 
-  if (vec_len (root_rp->client_pids) == 0)
+  if (!is_client && vec_len (root_rp->client_pids) == 0)
     svm_region_unlink (root_rp);
 
   region_unlock (root_rp);
@@ -1202,6 +1219,18 @@ found:
 }
 
 void
+svm_region_exit (void)
+{
+  svm_region_exit_internal (0 /* is_client */ );
+}
+
+void
+svm_region_exit_client (void)
+{
+  svm_region_exit_internal (1 /* is_client */ );
+}
+
+void
 svm_client_scan_this_region_nolock (svm_region_t * rp)
 {
   int j;
diff --git a/src/svm/svm_common.h b/src/svm/svm_common.h
index c650165b4cf..e523da50db6 100644
--- a/src/svm/svm_common.h
+++ b/src/svm/svm_common.h
@@ -118,7 +118,9 @@ int svm_region_init_chroot (const char *root_path);
 void svm_region_init_chroot_uid_gid (const char *root_path, int uid, int gid);
 void svm_region_init_args (svm_map_region_args_t * a);
 void svm_region_exit (void);
+void svm_region_exit_client (void);
 void svm_region_unmap (void *rp_arg);
+void svm_region_unmap_client (void *rp_arg);
 void svm_client_scan (const char *root_path);
 void svm_client_scan_this_region_nolock (svm_region_t * rp);
 u8 *shm_name_from_svm_map_region_args (svm_map_region_args_t * a);