linux-kernel - Re: [PATCH 2/4] x86/alternatives: Don't need text_mutex when text

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Date:   Sun, 29 Oct 2017 09:20:01 +0800
From:   zhouchengming <zhouchengming1@...wei.com>
To:     Zhou Chengming <zhouchengming1@...wei.com>
CC:     <mhiramat@...nel.org>, <bp@...e.de>, <peterz@...radead.org>,
        <ananth@...ux.vnet.ibm.com>, <anil.s.keshavamurthy@...el.com>,
        <davem@...emloft.net>, <tglx@...utronix.de>, <jkosina@...e.cz>,
        <rostedt@...dmis.org>, <mjurczyk@...gle.com>, <x86@...nel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/4] x86/alternatives: Don't need text_mutex when text_poke()
 on UP

Oops, this is very wrong. Please ignore this patchset.  Sorry for the noise...

Thanks!

On 2017/10/28 20:50, Zhou Chengming wrote:
> The alternatives_smp_lock/unlock only be used on UP, so we don't
> need to hold the text_mutex when text_poke(). Then in the next patch,
> we can remove the outside smp_alt mutex too.
>
> Signed-off-by: Zhou Chengming<zhouchengming1@...wei.com>
> ---
>   arch/x86/kernel/alternative.c | 4 ----
>   1 file changed, 4 deletions(-)
>
> diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
> index 8549269..5c3f593 100644
> --- a/arch/x86/kernel/alternative.c
> +++ b/arch/x86/kernel/alternative.c
> @@ -442,7 +442,6 @@ static void alternatives_smp_lock(const s32 *start, const s32 *end,
>   {
>   	const s32 *poff;
>
> -	mutex_lock(&text_mutex);
>   	for (poff = start; poff<  end; poff++) {
>   		u8 *ptr = (u8 *)poff + *poff;
>
> @@ -452,7 +451,6 @@ static void alternatives_smp_lock(const s32 *start, const s32 *end,
>   		if (*ptr == 0x3e)
>   			text_poke(ptr, ((unsigned char []){0xf0}), 1);
>   	}
> -	mutex_unlock(&text_mutex);
>   }
>
>   static void alternatives_smp_unlock(const s32 *start, const s32 *end,
> @@ -460,7 +458,6 @@ static void alternatives_smp_unlock(const s32 *start, const s32 *end,
>   {
>   	const s32 *poff;
>
> -	mutex_lock(&text_mutex);
>   	for (poff = start; poff<  end; poff++) {
>   		u8 *ptr = (u8 *)poff + *poff;
>
> @@ -470,7 +467,6 @@ static void alternatives_smp_unlock(const s32 *start, const s32 *end,
>   		if (*ptr == 0xf0)
>   			text_poke(ptr, ((unsigned char []){0x3E}), 1);
>   	}
> -	mutex_unlock(&text_mutex);
>   }
>
>   struct smp_alt_module {