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Date: Sun, 24 Apr 2022 15:33:57 +0800 From: Guo Ren <guoren@...nel.org> To: Palmer Dabbelt <palmer@...belt.com> Cc: Arnd Bergmann <arnd@...db.de>, linux-arch <linux-arch@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-riscv <linux-riscv@...ts.infradead.org>, Guo Ren <guoren@...ux.alibaba.com>, Masami Hiramatsu <mhiramat@...nel.org>, stable@...r.kernel.org Subject: Re: [PATCH V3] riscv: patch_text: Fixup last cpu should be master On Sat, Apr 23, 2022 at 12:02 AM Palmer Dabbelt <palmer@...belt.com> wrote: > > On Thu, 21 Apr 2022 15:57:32 PDT (-0700), Palmer Dabbelt wrote: > > On Wed, 06 Apr 2022 07:16:49 PDT (-0700), guoren@...nel.org wrote: > >> From: Guo Ren <guoren@...ux.alibaba.com> > >> > >> 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@...ux.alibaba.com> > >> Signed-off-by: Guo Ren <guoren@...nel.org> > >> Acked-by: Palmer Dabbelt <palmer@...osinc.com> > >> Reviewed-by: Masami Hiramatsu <mhiramat@...nel.org> > >> Cc: <stable@...r.kernel.org> > >> --- > >> arch/riscv/kernel/patch.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c > >> index 0b552873a577..765004b60513 100644 > >> --- a/arch/riscv/kernel/patch.c > >> +++ b/arch/riscv/kernel/patch.c > >> @@ -104,7 +104,7 @@ 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)); > > > > Thanks, this is on fixes. > > Sorry, I forgot to add the Fixes and stable tags. I just fixed that up, > but I'm going to hold off on this one until next week's PR to make sure > it has time to go through linux-next. https://lore.kernel.org/linux-riscv/20220407073323.743224-3-guoren@kernel.org/ -- Best Regards Guo Ren ML: https://lore.kernel.org/linux-csky/
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