tracehook: wait_task_inactive

This extends wait_task_inactive() with a new argument so it can be used in
a "soft" mode where it will check for the task changing state unexpectedly
and back off.  There is no change to existing callers.  This lays the
groundwork to allow robust, noninvasive tracing that can try to sample a
blocked thread but back off safely if it wakes up.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/ia64/kernel/perfmon.c b/arch/ia64/kernel/perfmon.c
index 19d4493c6193..fc8f3509df27 100644
--- a/arch/ia64/kernel/perfmon.c
+++ b/arch/ia64/kernel/perfmon.c
@@ -2626,7 +2626,7 @@ pfm_task_incompatible(pfm_context_t *ctx, struct task_struct *task)
         /*
          * make sure the task is off any CPU
          */
-        wait_task_inactive(task);
+        wait_task_inactive(task, 0);
 
         /* more to come... */
 
@@ -4774,7 +4774,7 @@ recheck:
 
                 UNPROTECT_CTX(ctx, flags);
 
-                wait_task_inactive(task);
+                wait_task_inactive(task, 0);
 
                 PROTECT_CTX(ctx, flags);