On Tue, 4 Dec 2018 at 18:26, Steven Rostedt [off-list ref] wrote:

On Tue, 4 Dec 2018 11:12:43 +0000
Will Deacon [off-list ref] wrote:

quoted

quoted

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 8ef9fc226037..42e89397778b 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c

@@ -2393,11 +2393,14 @@ void __weak ftrace_replace_code(int enable)
 {
    struct dyn_ftrace *rec;
    struct ftrace_page *pg;
+   bool schedulable;
    int failed;

    if (unlikely(ftrace_disabled))
            return;

+   schedulable = !irqs_disabled() & !preempt_count();

Looks suspiciously like a bitwise preemptible() to me!

Ah, thanks. Yeah, that should have been &&. But what did you expect.
I didn't even compile this ;-)

quoted

quoted

+
    do_for_each_ftrace_rec(pg, rec) {

            if (rec->flags & FTRACE_FL_DISABLED)

@@ -2409,6 +2412,8 @@ void __weak ftrace_replace_code(int enable)
                    /* Stop processing */
                    return;
            }
+           if (schedulable)
+                   cond_resched();
    } while_for_each_ftrace_rec();
 }

If this solves the problem in core code, them I'm all for it. Otherwise, I
was thinking of rolling our own ftrace_replace_code() for arm64, but that's
going to involve a fair amount of duplication.

If it does, then I'll add it. Or take a patch for it ;-)

I tested your patch. it worked.

I'll send a patch shortly.

Cheers,
Anders

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