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[PATCH v3 0/2] arm64: stop using kstop_machine for ftrace

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  [PATCH v3 0/2] arm64: stop using kstop_machine for ftrace Li Bin <huawei.libin@huawei.com> - 2015-12-04 04:50 +0100
    [PATCH v3 1/2] arm64: ftrace: stop using kstop_machine to enable/disable tracing Li Bin <huawei.libin@huawei.com> - 2015-12-04 05:00 +0100
    Re: [PATCH v3 0/2] arm64: stop using kstop_machine for ftrace Will Deacon <will.deacon@arm.com> - 2015-12-04 13:10 +0100

#1283573 — [PATCH v3 0/2] arm64: stop using kstop_machine for ftrace

v2:
Based on the comments from Will and Steve,
1. Modify the commit message
2. Fix the misleading comments for ftrace_modify_code

v3:
Modify the comments again based on the comment from Steve.

Link: https://lkml.org/lkml/2015/12/3/422

Li Bin (2):
  arm64: ftrace: stop using kstop_machine to enable/disable tracing
  arm64: ftrace: fix the comments for ftrace_modify_code

 arch/arm64/kernel/ftrace.c |   16 ++++++++++------
 1 files changed, 10 insertions(+), 6 deletions(-)

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#1283574 — [PATCH v3 1/2] arm64: ftrace: stop using kstop_machine to enable/disable tracing

For ftrace on arm64, kstop_machine which is hugely disruptive
to a running system is not needed to convert nops to ftrace calls
or back, because that to be modified instrucions, that NOP, B or BL,
are all safe instructions which called "concurrent modification
and execution of instructions", that can be executed by one
thread of execution as they are being modified by another thread
of execution without requiring explicit synchronization.

Signed-off-by: Li Bin <huawei.libin@huawei.com>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
---
 arch/arm64/kernel/ftrace.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
index c851be7..9669b33 100644
--- a/arch/arm64/kernel/ftrace.c
+++ b/arch/arm64/kernel/ftrace.c
@@ -93,6 +93,11 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
 	return ftrace_modify_code(pc, old, new, true);
 }
 
+void arch_ftrace_update_code(int command)
+{
+	ftrace_modify_all_code(command);
+}
+
 int __init ftrace_dyn_arch_init(void)
 {
 	return 0;
-- 
1.7.1

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#1283767

On Fri, Dec 04, 2015 at 11:38:38AM +0800, Li Bin wrote:
> v2:
> Based on the comments from Will and Steve,
> 1. Modify the commit message
> 2. Fix the misleading comments for ftrace_modify_code
> 
> v3:
> Modify the comments again based on the comment from Steve.
> 
> Link: https://lkml.org/lkml/2015/12/3/422
> 
> Li Bin (2):
>   arm64: ftrace: stop using kstop_machine to enable/disable tracing
>   arm64: ftrace: fix the comments for ftrace_modify_code

Thanks, I'll queue both of these for 4.5.

Will
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