Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Fri, 15 Feb 2019 01:10:33 +0200
From: Igor Stoppa <>
To: Peter Zijlstra <>
Cc: Igor Stoppa <>,
 Andy Lutomirski <>, Nadav Amit <>,
 Matthew Wilcox <>, Kees Cook <>,
 Dave Hansen <>,
 Mimi Zohar <>,
 Thiago Jung Bauermann <>,
 Ahmed Soliman <>,,,,
Subject: Re: [RFC PATCH v5 03/12] __wr_after_init: Core and default arch

On 14/02/2019 13:28, Peter Zijlstra wrote:
> On Thu, Feb 14, 2019 at 12:41:32AM +0200, Igor Stoppa wrote:


>> +#define wr_rcu_assign_pointer(p, v) ({	\
>> +	smp_mb();			\
>> +	wr_assign(p, v);		\
>> +	p;				\
>> +})
> This requires that wr_memcpy() (through wr_assign) is single-copy-atomic
> for native types. There is not a comment in sight that states this.

Right, I kinda expected native-aligned <-> atomic, but it's not 
necessarily true. It should be confirmed when enabling write rare on a 
new architecture. I'll add the comment.

> Also, is this true of x86/arm64 memcpy ?

For x86_64: 
  the mov"itype"  part should deal with atomic copy of native, aligned 

For arm64: 
.Ltiny15 deals with copying less than 16 bytes, which includes pointers. 
When the data is aligned, the copy of a pointer should be atomic.


Powered by blists - more mailing lists

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.