From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0EDD58F54 for ; Mon, 22 Jul 2024 03:09:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721617775; cv=none; b=uGNl/HNFMZ60Rn9GVlzYJSYlDy0lQ+BFo/5b40YO+WQ5R9s7596NycpcQL6092Wh7fiCpd0NUK+s3gwep04OBX7WJQ68ROwCKjxV9lllBTfDtH2WIafUBvIFgN/w8XOFr/WFdPS6JpZbrDvAnHIH+xU+eSDyGMjm1VHu7lOHAlo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721617775; c=relaxed/simple; bh=N78WybtYPkcIyt5my0EMie9U5JakpXy+mFWGzPNcVkY=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=rsesKOPwN9siz6PpxMiYYf37gW5FlnHCt3mXWE/Ysg+lmVk/oMY+hk/Bj5CbRZRZYII6o//n6S3cMw2vLrhruxz1MorNeffvGqbL02DBJP4R/6/C1VgNwHKRYRQG4gg0hu5WMSwxaPSPBs/doVz3fPuni831CeHjQ9PhBYgCyQY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=Wgib+OoR; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Wgib+OoR" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1721617771; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=etqba8606LAa8l3O5OcOh1bnE+W9ImDVfH1gaX+xcJQ=; b=Wgib+OoRT/SP4ZiYJGc/ML5Bkab7C3HtR79A+sH8Te2cQxOWxg2XyFD1cyiyPSu0MqvYdD p5+DJ7c6R/y4PmRyGRe8j03eLp+hLh1n5KoSTaI8//bWHSaVsY2BPfFQQqpMNLG8ET9Dt9 SVTXx/ei6IaAnMnHbbybVKUHQ7IdI5Q= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-433-VZIGa3EQMGW6rcPIHnd04A-1; Sun, 21 Jul 2024 23:09:29 -0400 X-MC-Unique: VZIGa3EQMGW6rcPIHnd04A-1 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0746919560A1; Mon, 22 Jul 2024 03:09:28 +0000 (UTC) Received: from localhost (unknown [10.72.112.6]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 88C511955E7B; Mon, 22 Jul 2024 03:09:25 +0000 (UTC) Date: Mon, 22 Jul 2024 11:09:17 +0800 From: Baoquan He To: Uros Bizjak Cc: akpm@linux-foundation.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Eric Biederman Subject: Re: [PATCH] kexec: Use atomic_try_cmpxchg_acquire() in kexec_trylock() Message-ID: References: <20240719103937.53742-1-ubizjak@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240719103937.53742-1-ubizjak@gmail.com> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 On 07/19/24 at 12:38pm, Uros Bizjak wrote: > Use atomic_try_cmpxchg_acquire(*ptr, &old, new) instead of > atomic_cmpxchg_acquire(*ptr, old, new) == old in kexec_trylock(). > x86 CMPXCHG instruction returns success in ZF flag, so > this change saves a compare after cmpxchg. Seems it can simplify code even though on non-x86 arch, should we replace atomic_try_cmpxchg_acquire() with atomic_try_cmpxchg_acquire() in all similar places? For this one, Acked-by: Baoquan He > > Signed-off-by: Uros Bizjak > Cc: Eric Biederman > --- > kernel/kexec_internal.h | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/kernel/kexec_internal.h b/kernel/kexec_internal.h > index 2595defe8c0d..d35d9792402d 100644 > --- a/kernel/kexec_internal.h > +++ b/kernel/kexec_internal.h > @@ -23,7 +23,8 @@ int kimage_is_destination_range(struct kimage *image, > extern atomic_t __kexec_lock; > static inline bool kexec_trylock(void) > { > - return atomic_cmpxchg_acquire(&__kexec_lock, 0, 1) == 0; > + int old = 0; > + return atomic_try_cmpxchg_acquire(&__kexec_lock, &old, 1); > } > static inline void kexec_unlock(void) > { > -- > 2.42.0 > > > _______________________________________________ > kexec mailing list > kexec@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec >