From: Dave Young <dyoung@redhat.com>
To: tj@kernel.org, xiyou.wangcong@gmail.com,
kexec@lists.infradead.org, tim@edgecast.com,
linux-kernel@vger.kernel.org
Subject: [PATCH] percpu: add comment to per_cpu_ptr_to_phys
Date: Wed, 23 Nov 2011 16:45:43 +0800 [thread overview]
Message-ID: <20111123084543.GA2923@darkstar.nay.redhat.com> (raw)
add comments about current per_cpu_ptr_to_phys implementation
to explain why the logic is more complicated than necessary.
Signed-off-by: Dave Young <dyoung@redhat.com>
---
mm/percpu.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
--- linux-2.6.orig/mm/percpu.c 2011-11-22 10:18:46.000000000 +0800
+++ linux-2.6/mm/percpu.c 2011-11-23 16:27:01.667562973 +0800
@@ -988,6 +988,19 @@ phys_addr_t per_cpu_ptr_to_phys(void *ad
unsigned int cpu;
/*
+ * percpu allocator has special setup for the first chunk,
+ * which currently supports either embedding in linear address space
+ * or vmalloc mapping, and, from the second one, the backing
+ * allocator (currently either vm or km) provides translation.
+ *
+ * The addr can be tranlated simply without checking if it falls
+ * into the first chunk. But the current code reflects better
+ * how percpu allocator actually works, and the verification can
+ * discover both bugs in percpu allocator itself and
+ * per_cpu_ptr_to_phys() callers. So we keep current code.
+ */
+
+ /*
* The following test on first_start/end isn't strictly
* necessary but will speed up lookups of addresses which
* aren't in the first chunk.
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WARNING: multiple messages have this Message-ID (diff)
From: Dave Young <dyoung@redhat.com>
To: tj@kernel.org, xiyou.wangcong@gmail.com,
kexec@lists.infradead.org, tim@edgecast.com,
linux-kernel@vger.kernel.org
Subject: [PATCH] percpu: add comment to per_cpu_ptr_to_phys
Date: Wed, 23 Nov 2011 16:45:43 +0800 [thread overview]
Message-ID: <20111123084543.GA2923@darkstar.nay.redhat.com> (raw)
add comments about current per_cpu_ptr_to_phys implementation
to explain why the logic is more complicated than necessary.
Signed-off-by: Dave Young <dyoung@redhat.com>
---
mm/percpu.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
--- linux-2.6.orig/mm/percpu.c 2011-11-22 10:18:46.000000000 +0800
+++ linux-2.6/mm/percpu.c 2011-11-23 16:27:01.667562973 +0800
@@ -988,6 +988,19 @@ phys_addr_t per_cpu_ptr_to_phys(void *ad
unsigned int cpu;
/*
+ * percpu allocator has special setup for the first chunk,
+ * which currently supports either embedding in linear address space
+ * or vmalloc mapping, and, from the second one, the backing
+ * allocator (currently either vm or km) provides translation.
+ *
+ * The addr can be tranlated simply without checking if it falls
+ * into the first chunk. But the current code reflects better
+ * how percpu allocator actually works, and the verification can
+ * discover both bugs in percpu allocator itself and
+ * per_cpu_ptr_to_phys() callers. So we keep current code.
+ */
+
+ /*
* The following test on first_start/end isn't strictly
* necessary but will speed up lookups of addresses which
* aren't in the first chunk.
next reply other threads:[~2011-11-23 8:43 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-23 8:45 Dave Young [this message]
2011-11-23 8:45 ` [PATCH] percpu: add comment to per_cpu_ptr_to_phys Dave Young
2011-11-23 16:22 ` Tejun Heo
2011-11-23 16:22 ` Tejun Heo
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