[PATCH] alpha: Fix getxpid on alpha so it works for threads.

[Eric W. Biederman]

While looking in the code I discovered that
alpha has fallen behind because it doesn't use sys_getppid.
The problem is that it doesn't follow the task struct
to the task_group_leader.

The following (untested) patch should fix the problem.

Eric


---

 arch/alpha/kernel/asm-offsets.c |    1 +
 arch/alpha/kernel/entry.S       |   16 +++++++++-------
 2 files changed, 10 insertions(+), 7 deletions(-)

df0f0250c67ba8366c3c70570412b8dee08bd710
diff --git a/arch/alpha/kernel/asm-offsets.c b/arch/alpha/kernel/asm-offsets.c
index 8f2e5c7..6c56c75 100644
--- a/arch/alpha/kernel/asm-offsets.c
+++ b/arch/alpha/kernel/asm-offsets.c
@@ -28,6 +28,7 @@ void foo(void)
         DEFINE(TASK_GID, offsetof(struct task_struct, gid));
         DEFINE(TASK_EGID, offsetof(struct task_struct, egid));
         DEFINE(TASK_REAL_PARENT, offsetof(struct task_struct, real_parent));
+        DEFINE(TASK_GROUP_LEADER, offsetof(struct task_struct, group_leader));
         DEFINE(TASK_TGID, offsetof(struct task_struct, tgid));
         BLANK();
 
diff --git a/arch/alpha/kernel/entry.S b/arch/alpha/kernel/entry.S
index e38671c..7af15bf 100644
--- a/arch/alpha/kernel/entry.S
+++ b/arch/alpha/kernel/entry.S
@@ -879,17 +879,19 @@ sys_getxpid:
 
 	/* See linux/kernel/timer.c sys_getppid for discussion
 	   about this loop.  */
-	ldq	$3, TASK_REAL_PARENT($2)
-1:	ldl	$1, TASK_TGID($3)
+	ldq	$3, TASK_GROUP_LEADER($2)
+	ldq	$4, TASK_REAL_PARENT($3)
+	ldl	$0, TASK_TGID($2)
+1:	ldl	$1, TASK_TGID($4)
 #ifdef CONFIG_SMP
-	mov	$3, $4
+	mov	$4, $5
 	mb
-	ldq	$3, TASK_REAL_PARENT($2)
-	cmpeq	$3, $4, $4
-	beq	$4, 1b
+	ldq	$3, TASK_GROUP_LEADER($2)
+	ldq	$4, TASK_REAL_PARENT($3)
+	cmpeq	$4, $5, $5
+	beq	$5, 1b
 #endif
 	stq	$1, 80($sp)
-	ldl	$0, TASK_TGID($2)
 	ret
 .end sys_getxpid
 
-- 
1.1.3.g5c7d

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