[Xen-devel] [PATCH RFC v2 09/13] libxl: introduce lock in libxl_ctx

[Ian Jackson <ian.jackson@xxxxxxxxxxxxx>]

This lock will be used to protect data structures which will be hung
off the libxl_ctx in subsequent patches.

Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
---
 tools/libxl/libxl.c          |    3 +++
 tools/libxl/libxl_internal.h |   16 ++++++++++++++++
 2 files changed, 19 insertions(+), 0 deletions(-)

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 5d448af..a3c9807 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -40,6 +40,7 @@ int libxl_ctx_alloc(libxl_ctx **pctx, int version, 
xentoollog_logger * lg)
 {
     libxl_ctx *ctx;
     struct stat stat_buf;
+    const pthread_mutex_t mutex_value = PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP;
 
     if (version != LIBXL_VERSION)
         return ERROR_VERSION;
@@ -53,6 +54,8 @@ int libxl_ctx_alloc(libxl_ctx **pctx, int version, 
xentoollog_logger * lg)
     memset(ctx, 0, sizeof(libxl_ctx));
     ctx->lg = lg;
 
+    memcpy(&ctx->lock, &mutex_value, sizeof(ctx->lock));
+
     if ( stat(XENSTORE_PID_FILE, &stat_buf) != 0 ) {
         LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "Is xenstore daemon running?\n"
                      "failed to stat %s", XENSTORE_PID_FILE);
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 6d9da2c..79a9de4 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -23,6 +23,7 @@
 #include <stdarg.h>
 #include <stdlib.h>
 #include <string.h>
+#include <pthread.h>
 
 #include <xs.h>
 #include <xenctrl.h>
@@ -95,6 +96,9 @@ struct libxl__ctx {
     xc_interface *xch;
     struct xs_handle *xsh;
 
+    pthread_mutex_t lock; /* protects data structures hanging off the ctx */
+      /* always use MUTEX_LOCK and MUTEX_UNLOCK to manipulate this */
+
     /* for callers who reap children willy-nilly; caller must only
      * set this after libxl_init and before any other call - or
      * may leave them untouched */
@@ -577,6 +581,18 @@ _hidden libxl__json_object *libxl__json_parse(libxl__gc 
*gc, const char *s);
 #define CTX           libxl__gc_owner(gc)
 
 
+#define MUTEX_LOCK do {                                 \
+        int mutex_r = pthread_mutex_lock(&CTX->lock);   \
+        assert(!mutex_r);                               \
+    } while(0)
+
+#define MUTEX_UNLOCK do {                               \
+        int mutex_r = pthread_mutex_unlock(&CTX->lock); \
+        assert(!mutex_r);                               \
+    } while(0)
+        
+
+
 /*
  * Inserts "elm_new" into the sorted list "head".
  *
-- 
1.7.2.5


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