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Subject[PATCH 3/3] arm64: ftrace: add cond_resched() to func ftrace_make_(call|nop)
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Both of those functions end up calling ftrace_modify_code(), which is
expensive because it changes the page tables and flush caches.
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
occasionally.
Rework so that we call cond_resched() before going into the
ftrace_modify_code() function.

Co-developed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Anders Roxell <anders.roxell@linaro.org>
---
arch/arm64/kernel/ftrace.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
index de1a397d2d3f..9da38da58df7 100644
--- a/arch/arm64/kernel/ftrace.c
+++ b/arch/arm64/kernel/ftrace.c
@@ -130,6 +130,11 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
old = aarch64_insn_gen_nop();
new = aarch64_insn_gen_branch_imm(pc, addr, AARCH64_INSN_BRANCH_LINK);

+ /* This function can take a long time when sanitizers are enabled, so
+ * lets make sure we allow RCU processing.
+ */
+ cond_resched();
+
return ftrace_modify_code(pc, old, new, true);
}

@@ -188,6 +193,11 @@ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,

new = aarch64_insn_gen_nop();

+ /* This function can take a long time when sanitizers are enabled, so
+ * lets make sure we allow RCU processing.
+ */
+ cond_resched();
+
return ftrace_modify_code(pc, old, new, validate);
}

--
2.19.2
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