[Xen-devel] [PATCH] xl: remove all local "ctx" variables

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

# HG changeset patch
# User Ian Campbell <ian.campbell@xxxxxxxxxx>
# Date 1337180254 -3600
# Node ID 3f65f6466bf6008a2cccc374ffd9ab799dd41da4
# Parent  c8af0666c1448bbdcb3fddc155c6cc1978bc0206
xl: remove all local "ctx" variables.

xl has a global "ctx" variable, so there should be no need to pass a
ctx to any function.

The exception is to functions which are used as libxl callbacks. In
this case the ctx passed to the callback must necessarily always be
the same as the global one and so we rename the parameter version to
ctx_unused.

This fixes a hang/deadlock with console autoconnect. postfork() would
correctly replace the global ctx with a new one in the child, but
autoconnect_console() would continue using the old context via the
local variable (i.e. the parent's context) leading to deadlock on the
xenstore handle (which cannot be reliably shared between guests).

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

diff -r c8af0666c144 -r 3f65f6466bf6 tools/libxl/xl.c
--- a/tools/libxl/xl.c  Wed May 16 14:37:25 2012 +0100
+++ b/tools/libxl/xl.c  Wed May 16 15:57:34 2012 +0100
@@ -108,7 +108,7 @@ void postfork(void)
     }
 }
 
-pid_t xl_fork(libxl_ctx *ctx) {
+pid_t xl_fork(void) {
     pid_t pid;
 
     pid = fork();
diff -r c8af0666c144 -r 3f65f6466bf6 tools/libxl/xl.h
--- a/tools/libxl/xl.h  Wed May 16 14:37:25 2012 +0100
+++ b/tools/libxl/xl.h  Wed May 16 15:57:34 2012 +0100
@@ -107,7 +107,7 @@ struct cmd_spec *cmdtable_lookup(const c
 
 extern libxl_ctx *ctx;
 extern xentoollog_logger_stdiostream *logger;
-pid_t xl_fork(libxl_ctx *ctx); /* like fork, but prints and dies if it fails */
+pid_t xl_fork(void); /* like fork, but prints and dies if it fails */
 void postfork(void);
 
 /* global options */
diff -r c8af0666c144 -r 3f65f6466bf6 tools/libxl/xl_cmdimpl.c
--- a/tools/libxl/xl_cmdimpl.c  Wed May 16 14:37:25 2012 +0100
+++ b/tools/libxl/xl_cmdimpl.c  Wed May 16 15:57:34 2012 +0100
@@ -1298,7 +1298,7 @@ skip_vfb:
     xlu_cfg_destroy(config);
 }
 
-static void reload_domain_config(libxl_ctx *ctx, uint32_t domid,
+static void reload_domain_config(uint32_t domid,
                                  uint8_t **config_data, int *config_len)
 {
     uint8_t *t_data;
@@ -1318,7 +1318,7 @@ static void reload_domain_config(libxl_c
 
 /* Returns 1 if domain should be restarted,
  * 2 if domain should be renamed then restarted, or 0 */
-static int handle_domain_death(libxl_ctx *ctx, uint32_t domid,
+static int handle_domain_death(uint32_t domid,
                                libxl_event *event,
                                uint8_t **config_data, int *config_len,
                                libxl_domain_config *d_config)
@@ -1377,12 +1377,12 @@ static int handle_domain_death(libxl_ctx
         break;
 
     case LIBXL_ACTION_ON_SHUTDOWN_RESTART_RENAME:
-        reload_domain_config(ctx, domid, config_data, config_len);
+        reload_domain_config(domid, config_data, config_len);
         restart = 2;
         break;
 
     case LIBXL_ACTION_ON_SHUTDOWN_RESTART:
-        reload_domain_config(ctx, domid, config_data, config_len);
+        reload_domain_config(domid, config_data, config_len);
 
         restart = 1;
         /* fall-through */
@@ -1418,7 +1418,7 @@ static void replace_string(char **str, c
 }
 
 
-static int preserve_domain(libxl_ctx *ctx, uint32_t domid, libxl_event *event,
+static int preserve_domain(uint32_t domid, libxl_event *event,
                            libxl_domain_config *d_config)
 {
     time_t now;
@@ -1496,7 +1496,7 @@ static int freemem(libxl_domain_build_in
     return ERROR_NOMEM;
 }
 
-static void autoconnect_console(libxl_ctx *ctx, libxl_event *ev, void *priv)
+static void autoconnect_console(libxl_ctx *ctx_ignored, libxl_event *ev, void 
*priv)
 {
     pid_t *pid = priv;
 
@@ -1811,7 +1811,7 @@ start:
         pid_t child1, got_child;
         int nullfd;
 
-        child1 = xl_fork(ctx);
+        child1 = xl_fork();
         if (child1) {
             printf("Daemon running with PID %d\n", child1);
 
@@ -1889,11 +1889,11 @@ start:
             LOG("Domain %d has shut down, reason code %d 0x%x", domid,
                 event->u.domain_shutdown.shutdown_reason,
                 event->u.domain_shutdown.shutdown_reason);
-            switch (handle_domain_death(ctx, domid, event,
+            switch (handle_domain_death(domid, event,
                                         (uint8_t **)&config_data, &config_len,
                                         &d_config)) {
             case 2:
-                if (!preserve_domain(ctx, domid, event, &d_config)) {
+                if (!preserve_domain(domid, event, &d_config)) {
                     /* If we fail then exit leaving the old domain in place. */
                     ret = -1;
                     goto out;
@@ -2929,7 +2929,7 @@ static void migrate_domain(const char *d
     MUST( libxl_pipe(ctx, sendpipe) );
     MUST( libxl_pipe(ctx, recvpipe) );
 
-    child = xl_fork(ctx);
+    child = xl_fork();
 
     if (!child) {
         dup2(sendpipe[0], 0);

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