Subject: perfmon2: don't try ptrace_check_attach

From: Arnd Bergmann <arnd.bergmann@de.ibm.com>

ptrace_check_attach has been removed with the move to utrace,
which breaks perfmon2. This tries to work around the problem
with minimal breakage, but some functionality is missing for
now.

More info from Kevin Corry:
There are three ways you can do hardware-counter monitoring with
Perfmon2:
   1) System-wide, where you monitor all processes on one or more CPUs.
   2) Per-process self-monitored, where a process monitors only itself.
   3) Per-process externally-monitored, where one process monitors
      another single process.

Number 3 above breaks with the ptrace/utrace changes, since Perfmon2
currently enforces that the monitored process must be ptraced and stopped
by the monitoring process in order to perform certain Perfmon2 system
calls on the monitored process.

Cc: Kevin Corry <kevcorry@us.ibm.com>
Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>

Index: linux-2.6/perfmon/perfmon_syscalls.c
===================================================================
--- linux-2.6.orig/perfmon/perfmon_syscalls.c
+++ linux-2.6/perfmon/perfmon_syscalls.c
@@ -155,8 +155,8 @@ int pfm_get_task(struct pfm_context *ctx
 	 * returns 0 if cannot attach
 	 */
 	ret1 = ptrace_may_attach(p);
-	if (ret1)
-		ret = ptrace_check_attach(p, 0);
+//	if (ret1)
+//		ret = ptrace_check_attach(p, 0);
 
 	PFM_DBG("may_attach=%d check_attach=%d", ret1, ret);
 
@@ -276,7 +276,7 @@ recheck:
 		/*
 		 * check that the thread is ptraced AND STOPPED
 		 */
-		ret = ptrace_check_attach(task, 0);
+		ret = -ESRCH; // ptrace_check_attach(task, 0);
 
 		spin_lock_irqsave(&ctx->lock, new_flags);