[SSI] openssi/kernel/fs/proc internal.h,1.5,1.6

Update of /cvsroot/ssic-linux/openssi/kernel/fs/proc
In directory sfp-cvsdas-3.v30.ch3.sourceforge.com:/tmp/cvs-serv1380/fs/proc

Modified Files:
      Tag: OPENSSI-FC
	internal.h 
Log Message:
- vproc_migrating: moved inline function from fs/proc/base.c here.

(#ifdef VPROC_HOLD_ZERO_GET_TASK)
- proc_ssi_task: borrow pvp_pproc's task_struct reference while PV_IS_LOCAL flag is set. there is no race with process migration because the client does not release pvp_pproc's task_struct reference until after atomically clearing the flag. there is no race with final put_task_struct() because the caller holds the reference to vproc struct which has the final task_struct reference unless the process has migrated.


Index: internal.h
===================================================================
RCS file: /cvsroot/ssic-linux/openssi/kernel/fs/proc/internal.h,v
retrieving revision 1.5
retrieving revision 1.6
diff -u -d -r1.5 -r1.6
--- internal.h	27 Oct 2009 03:18:30 -0000	1.5
+++ internal.h	17 Jan 2011 07:01:37 -0000	1.6
@@ -65,7 +65,44 @@
 #endif
 	return task;
 }
-#endif /* !VPROC_HOLD_ZERO_GET_TASK */
+#else /* !VPROC_HOLD_ZERO_GET_TASK */
+/**
+ * proc_ssi_task - borrow pvp_pproc's task_struct reference
+ * @vp: vproc structure of the task
+ *
+ * SMP-safe. The vproc structure has final task_struct reference unless the
+ * process has migrated in which case during migration pvp_pproc's task_struct
+ * reference is released after clearing PV_IS_LOCAL flag.
+ *
+ * Acquires and releases VPROC FLAG LOCK.
+ */
+static inline task_t *proc_ssi_task(struct vproc *vp)
+{
+	task_t *task;
+
+	VPROC_LOCK_FLAG(vp, "proc_ssi_task");
+	if (PVP(vp)->pvp_flag & PV_IS_LOCAL) {
+		task = PVP(vp)->pvp_pproc;
+		get_task_struct(task);
+	} else
+		task = NULL;
+	VPROC_UNLOCK_FLAG(vp, "proc_ssi_task");
+	return task;
+}
+#endif /* VPROC_HOLD_ZERO_GET_TASK */
+
+/* Determine whether pid is migrating in */
+static inline int vproc_migrating(struct vproc *vp)
+{
+#ifdef TASK_HOLD_VPROC
+	return (current->ppid == 2 &&
+		current->epid != vp->vp_pid &&
+		current->pid == vp->vp_pid);
+#else
+	return (current->ppid == 2 && current->p_vproc->vp_pid != vp->vp_pid &&
+			current->pid == vp->vp_pid);
+#endif
+}
 #endif /* CONFIG_SSI */
 
 extern void create_seq_entry(char *name, mode_t mode, struct file_operations *f);


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