linux-kernel - Re: [PATCH] percpu: Introduce a read-mostly percpu API

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Date:	Sat, 23 Oct 2010 04:25:45 +0200
From:	Michał Mirosław <mirq@...e.qmqm.pl>
To:	"H. Peter Anvin" <hpa@...ux.intel.com>
Cc:	Shaohua Li <shaohua.li@...el.com>, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] percpu: Introduce a read-mostly percpu API

Commit c957ef2c59e952803766ddc22e89981ab534606f that just went into
Linus' tree has a bug - only one of hunks was modified (.readmostly
moved after .page_aligned).


>commit c957ef2c59e952803766ddc22e89981ab534606f
>Author: Shaohua Li <shaohua.li@...el.com>
>Date:   Wed Oct 20 11:07:02 2010 +0800
>
>    percpu: Introduce a read-mostly percpu API
>    
>    Add a new readmostly percpu section and API.  This can be used to
>    avoid dirtying data lines which are generally not written to, which is
>    especially important for data which may be accessed by processors
>    other than the one for which the percpu area belongs to.
>    
>    [ hpa: moved it *after* the page-aligned section, for obvious
>      reasons. ]
>    
>    Signed-off-by: Shaohua Li <shaohua.li@...el.com>
>    LKML-Reference: <1287544022.4571.7.camel@...10-conroe.sh.intel.com>
>    Cc: Eric Dumazet <eric.dumazet@...il.com>
>    Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
>
>diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
>index 8a92a17..d7e7b21 100644
>--- a/include/asm-generic/vmlinux.lds.h
>+++ b/include/asm-generic/vmlinux.lds.h
>@@ -677,7 +677,9 @@
> 				- LOAD_OFFSET) {			\
> 		VMLINUX_SYMBOL(__per_cpu_start) = .;			\
> 		*(.data..percpu..first)					\
>+		. = ALIGN(PAGE_SIZE);					\
> 		*(.data..percpu..page_aligned)				\
>+		*(.data..percpu..readmostly)				\
> 		*(.data..percpu)					\
> 		*(.data..percpu..shared_aligned)			\
> 		VMLINUX_SYMBOL(__per_cpu_end) = .;			\
>@@ -703,6 +705,8 @@
> 		VMLINUX_SYMBOL(__per_cpu_load) = .;			\
> 		VMLINUX_SYMBOL(__per_cpu_start) = .;			\
> 		*(.data..percpu..first)					\
>+		. = ALIGN(PAGE_SIZE);					\
>+		*(.data..percpu..readmostly)				\
> 		*(.data..percpu..page_aligned)				\

Here.

> 		*(.data..percpu)					\
> 		*(.data..percpu..shared_aligned)			\
[...]

Best Regards,
Michał Mirosław
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