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Subject[PATCH v6 2/5] LoongArch: Use stop_machine_cpuslocked() to modify instruction
Date
Rename the current larch_insn_patch_text() to patch_text_nosync(),
then redefine larch_insn_patch_text() with stop_machine_cpuslocked()
to modify instruction to avoid CPU race, this is preparation for later
patch.

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
arch/loongarch/kernel/inst.c | 33 ++++++++++++++++++++++++++++++++-
1 file changed, 32 insertions(+), 1 deletion(-)

diff --git a/arch/loongarch/kernel/inst.c b/arch/loongarch/kernel/inst.c
index aaaf9de..d842405 100644
--- a/arch/loongarch/kernel/inst.c
+++ b/arch/loongarch/kernel/inst.c
@@ -3,6 +3,7 @@
* Copyright (C) 2020-2022 Loongson Technology Corporation Limited
*/
#include <linux/sizes.h>
+#include <linux/stop_machine.h>
#include <linux/uaccess.h>

#include <asm/cacheflush.h>
@@ -10,6 +11,12 @@

static DEFINE_RAW_SPINLOCK(patch_lock);

+struct patch_insn {
+ void *addr;
+ u32 insn;
+ atomic_t cpu_count;
+};
+
int larch_insn_read(void *addr, u32 *insnp)
{
int ret;
@@ -34,7 +41,7 @@ int larch_insn_write(void *addr, u32 insn)
return ret;
}

-int larch_insn_patch_text(void *addr, u32 insn)
+static int patch_text_nosync(void *addr, u32 insn)
{
int ret;
u32 *tp = addr;
@@ -50,6 +57,30 @@ int larch_insn_patch_text(void *addr, u32 insn)
return ret;
}

+static int patch_text_cb(void *data)
+{
+ struct patch_insn *param = data;
+ int ret = 0;
+
+ if (atomic_inc_return(&param->cpu_count) == num_online_cpus()) {
+ ret = patch_text_nosync(param->addr, param->insn);
+ atomic_inc(&param->cpu_count);
+ } else {
+ while (atomic_read(&param->cpu_count) <= num_online_cpus())
+ cpu_relax();
+ smp_mb();
+ }
+
+ return ret;
+}
+
+int larch_insn_patch_text(void *addr, u32 insn)
+{
+ struct patch_insn param = { addr, insn, ATOMIC_INIT(0) };
+
+ return stop_machine_cpuslocked(patch_text_cb, &param, cpu_online_mask);
+}
+
u32 larch_insn_gen_nop(void)
{
return INSN_NOP;
--
2.1.0
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