xenpaging: implement stopping of pager by sending SIGTERM/SIGINT

Write all paged-out pages back into the guest if the pager is
interrupted by ctrl-c or if it receives SIGTERM.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Committed-by: Ian Jackson <ian.jackson.citrix.com>

4 files changed, 104 insertions, 3 deletions

diff --git a/tools/xenpaging/Makefile b/tools/xenpaging/Makefile
index d312c9df41..6c20a8d52b 100644
--- a/tools/xenpaging/Makefile
+++ b/tools/xenpaging/Makefile
@@ -8,6 +8,7 @@ POLICY    = default
 
 SRC      :=
 SRCS     += file_ops.c xenpaging.c policy_$(POLICY).c
+SRCS     += pagein.c
 
 CFLAGS   += -Werror
 CFLAGS   += -Wno-unused
diff --git a/tools/xenpaging/pagein.c b/tools/xenpaging/pagein.c
new file mode 100644
index 0000000000..93552c0bfa
--- /dev/null
+++ b/tools/xenpaging/pagein.c
@@ -0,0 +1,68 @@
+/* Trigger a page-in in a separate thread-of-execution to avoid deadlock */
+#include <pthread.h>
+#include "xc_private.h"
+
+struct page_in_args {
+    domid_t dom;
+    xc_interface *xch;
+};
+
+static struct page_in_args page_in_args;
+static unsigned long page_in_gfn;
+static unsigned int page_in_possible;
+
+static pthread_t page_in_thread;
+static pthread_cond_t page_in_cond = PTHREAD_COND_INITIALIZER;
+static pthread_mutex_t page_in_mutex = PTHREAD_MUTEX_INITIALIZER;
+
+static void *page_in(void *arg)
+{
+    struct page_in_args *pia = arg;
+    void *page;
+    xen_pfn_t gfn;
+
+    while (1)
+    {
+        pthread_mutex_lock(&page_in_mutex);
+        while (!page_in_gfn)
+            pthread_cond_wait(&page_in_cond, &page_in_mutex);
+        gfn = page_in_gfn;
+        page_in_gfn = 0;
+        pthread_mutex_unlock(&page_in_mutex);
+
+        /* Ignore errors */
+        page = xc_map_foreign_pages(pia->xch, pia->dom, PROT_READ, &gfn, 1);
+        if (page)
+            munmap(page, PAGE_SIZE);
+    }
+    page_in_possible = 0;
+    pthread_exit(NULL);
+}
+
+void page_in_trigger(unsigned long gfn)
+{
+    if (!page_in_possible)
+        return;
+
+    pthread_mutex_lock(&page_in_mutex);
+    page_in_gfn = gfn;
+    pthread_mutex_unlock(&page_in_mutex);
+    pthread_cond_signal(&page_in_cond);
+}
+
+void create_page_in_thread(domid_t domain_id, xc_interface *xch)
+{
+    page_in_args.dom = domain_id;
+    page_in_args.xch = xch;
+    if (pthread_create(&page_in_thread, NULL, page_in, &page_in_args) == 0)
+        page_in_possible = 1;
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-set-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End: 
+ */
diff --git a/tools/xenpaging/xenpaging.c b/tools/xenpaging/xenpaging.c
index 55e00e60e3..14b64df968 100644
--- a/tools/xenpaging/xenpaging.c
+++ b/tools/xenpaging/xenpaging.c
@@ -650,6 +650,9 @@ int main(int argc, char *argv[])
     sigaction(SIGINT,  &act, NULL);
     sigaction(SIGALRM, &act, NULL);
 
+    /* listen for page-in events to stop pager */
+    create_page_in_thread(paging->mem_event.domain_id, xch);
+
     /* Evict pages */
     for ( i = 0; i < paging->num_pages; i++ )
     {
@@ -665,7 +668,7 @@ int main(int argc, char *argv[])
     DPRINTF("%d pages evicted. Done.\n", i);
 
     /* Swap pages in and out */
-    while ( !interrupted )
+    while ( 1 )
     {
         /* Wait for Xen to signal that a page needs paged in */
         rc = xenpaging_wait_for_event_or_timeout(paging);
@@ -728,8 +731,12 @@ int main(int argc, char *argv[])
                     goto out;
                 }
 
-                /* Evict a new page to replace the one we just paged in */
-                evict_victim(paging, &victims[i], fd, i);
+                /* Evict a new page to replace the one we just paged in,
+                 * or clear this pagefile slot on exit */
+                if ( interrupted )
+                    victims[i].gfn = INVALID_MFN;
+                else
+                    evict_victim(paging, &victims[i], fd, i);
             }
             else
             {
@@ -756,6 +763,28 @@ int main(int argc, char *argv[])
                 }
             }
         }
+
+        /* Write all pages back into the guest */
+        if ( interrupted == SIGTERM || interrupted == SIGINT )
+        {
+            for ( i = 0; i < paging->domain_info->max_pages; i++ )
+            {
+                if ( test_bit(i, paging->bitmap) )
+                {
+                    page_in_trigger(i);
+                    break;
+                }
+            }
+            /* If no more pages to process, exit loop */
+            if ( i == paging->domain_info->max_pages )
+                break;
+        }
+        else
+        {
+            /* Exit on any other signal */
+            if ( interrupted )
+                break;
+        }
     }
     DPRINTF("xenpaging got signal %d\n", interrupted);
 
diff --git a/tools/xenpaging/xenpaging.h b/tools/xenpaging/xenpaging.h
index 4cf50b0f85..36f4290248 100644
--- a/tools/xenpaging/xenpaging.h
+++ b/tools/xenpaging/xenpaging.h
@@ -53,6 +53,9 @@ typedef struct xenpaging_victim {
 } xenpaging_victim_t;
 
 
+extern void create_page_in_thread(domid_t domain_id, xc_interface *xch);
+extern void page_in_trigger(unsigned long gfn);
+
 #endif // __XEN_PAGING_H__