[v2,21/28] linux-user: Add debug code to exercise restarting system calls

Commit Message

Peter Maydell May 12, 2016, 5:47 p.m. UTC

From: Timothy E Baldwin <[e-mail]>

If DEBUG_ERESTARTSYS is set restart all system calls once. This
is pure debug code for exercising the syscall restart code paths
in the per-architecture cpu main loops.

Signed-off-by: Timothy Edward Baldwin <[e-mail]>
Message-id: [e-mail]
[PMM: Add comment and a commented-out #define next to the commented-out
 generic DEBUG #define; remove the check on TARGET_USE_ERESTARTSYS;
 tweak comment message]
Reviewed-by: Peter Maydell <[e-mail]>
Signed-off-by: Peter Maydell <[e-mail]>
---
 linux-user/syscall.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

Patch

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index a4a1af7..ced519d 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -110,6 +110,10 @@  int __clone2(int (*fn)(void *), void *child_stack_base,
     CLONE_PARENT_SETTID | CLONE_CHILD_SETTID | CLONE_CHILD_CLEARTID)
 
 //#define DEBUG
+/* Define DEBUG_ERESTARTSYS to force every syscall to be restarted
+ * once. This exercises the codepaths for restart.
+ */
+//#define DEBUG_ERESTARTSYS
 
 //#include <linux/msdos_fs.h>
 #define	VFAT_IOCTL_READDIR_BOTH		_IOR('r', 1, struct linux_dirent [2])
@@ -5871,6 +5875,21 @@  abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
     struct statfs stfs;
     void *p;
 
+#if defined(DEBUG_ERESTARTSYS)
+    /* Debug-only code for exercising the syscall-restart code paths
+     * in the per-architecture cpu main loops: restart every syscall
+     * the guest makes once before letting it through.
+     */
+    {
+        static int flag;
+
+        flag = !flag;
+        if (flag) {
+            return -TARGET_ERESTARTSYS;
+        }
+    }
+#endif
+
 #ifdef DEBUG
     gemu_log("syscall %d", num);
 #endif