From: Guo Ren guoren@linux.alibaba.com
commit 8ec1442953c66a1d8462cccd8c20b7ba561f5915 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: 043cb41a85de ("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 --- arch/riscv/kernel/patch.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/arch/riscv/kernel/patch.c +++ b/arch/riscv/kernel/patch.c @@ -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));