From da3d7682cb9e49d2054b1d6f9fbdacd430a65116 Mon Sep 17 00:00:00 2001 From: Anders Roxell Date: Tue, 4 Dec 2018 15:57:16 +0100 Subject: [PATCH] tracing: add cond_resched to ftrace_replace_code() When running in qemu on an kernel built with allmodconfig and debug options (in particular kcov and ubsan) enabled, ftrace_replace_code function call take minutes. The ftrace selftest calls ftrace_replace_code to look >40000 through ftrace_make_call/ftrace_make_nop, and these end up calling __aarch64_insn_write/aarch64_insn_patch_text_nosync. Microseconds add up because this is called in a loop for each dyn_ftrace record, and this triggers the softlockup watchdog unless we let it sleep occationally. Rework so that we call cond_resched() if preemptible(). Suggested-by: Steven Rostedt (VMware) Signed-off-by: Anders Roxell --- kernel/trace/ftrace.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index c375e33239f7..0c709e684465 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -2419,11 +2419,14 @@ 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(); + do_for_each_ftrace_rec(pg, rec) { if (rec->flags & FTRACE_FL_DISABLED) @@ -2435,6 +2438,8 @@ void __weak ftrace_replace_code(int enable) /* Stop processing */ return; } + if (schedulable) + cond_resched(); } while_for_each_ftrace_rec(); } -- 2.19.2