After the previous patch the "task == tt->this_task" checks in back_trace() and
is_task_active() lead to falsely "active" state if ACTIVE() && !LOCAL_ACTIVE().
This is easy to fix, but it seems to me that we can just simplify this logic and
remove the tt->this_task check from back_trace(), although I'm afraid I missed
something.
It look really simple: if LOCAL_ACTIVE() than "this_task" is /usr/bin/crash and
it is obviously running, otherwise we can never assume this if !task_has_cpu().
Not to mention that "deprecation of usage of has_cpu on non-SMP systems" looks
confusing, task_has_cpu() can work without VALID_MEMBER(task_struct_has_cpu).
BTW, I think that task_init() should use "on_cpu" if MEMBER_OFFSET_INIT(has_cpu)
fails, but this is off-topic.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
---
kernel.c | 3 +--
task.c | 8 +++-----
2 files changed, 4 insertions(+), 7 deletions(-)
diff --git a/kernel.c b/kernel.c
index c82b854..5a392fc 100644
--- a/kernel.c
+++ b/kernel.c
@@ -2800,8 +2800,7 @@ back_trace(struct bt_info *bt)
return;
}
- if (LIVE() && !(bt->flags & BT_EFRAME_SEARCH) &&
- ((bt->task == tt->this_task) || is_task_active(bt->task))) {
+ if (LIVE() && !(bt->flags & BT_EFRAME_SEARCH) && is_task_active(bt->task)) {
if (BT_REFERENCE_CHECK(bt) ||
bt->flags & (BT_TEXT_SYMBOLS_PRINT|BT_TEXT_SYMBOLS_NOPRINT))
diff --git a/task.c b/task.c
index fd4b700..a6bc9e7 100644
--- a/task.c
+++ b/task.c
@@ -5359,18 +5359,16 @@ is_task_active(ulong task)
{
int has_cpu;
+ if (LOCAL_ACTIVE() && (task == tt->this_task))
+ return TRUE;
if (DUMPFILE() && is_panic_thread(task))
return TRUE;
fill_task_struct(task);
- has_cpu = tt->last_task_read ?
+ has_cpu = tt->last_task_read ?
task_has_cpu(task, tt->task_struct) : 0;
- if (!(kt->flags & SMP) && !has_cpu && ACTIVE() &&
- (task == tt->this_task))
- has_cpu = TRUE;
-
return(has_cpu);
}
--
2.5.0
--
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