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riscv: patch_text: Fixup last cpu should be master

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commit 8ec1442953 upstream.

These patch_text implementations are using stop_machine_cpuslocked
infrastructure with atomic cpu_count. The original idea: When the
master CPU patch_text, the others should wait for it. But current
implementation is using the first CPU as master, which couldn't
guarantee the remaining CPUs are waiting. This patch changes the
last CPU as the master to solve the potential risk.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Fixes: 043cb41a85 ("riscv: introduce interfaces to patch kernel code")
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Guo Ren 2022-04-06 22:16:49 +08:00 • committed by Greg Kroah-Hartman
commit 8fcce58c59
1 changed files with 1 additions and 1 deletions
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2
arch/riscv/kernel/patch.c
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@ -100,7 +100,7 @@ static int patch_text_cb(void *data)
struct patch_insn *patch = data;
int ret = 0;
if (atomic_inc_return(&patch->cpu_count) == 1) {
if (atomic_inc_return(&patch->cpu_count) == num_online_cpus()) {
ret =
patch_text_nosync(patch->addr, &patch->insn,
GET_INSN_LENGTH(patch->insn));