Re: [RFC PATCH v5 03/12] __wr_after_init: Core and default arch

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 





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:
https://elixir.bootlin.com/linux/v5.0-rc6/source/arch/x86/include/asm/uaccess.h#L462 the mov"itype" part should deal with atomic copy of native, aligned types.


For arm64:
https://elixir.bootlin.com/linux/v5.0-rc6/source/arch/arm64/lib/copy_template.S#L110 .Ltiny15 deals with copying less than 16 bytes, which includes pointers. When the data is aligned, the copy of a pointer should be atomic.


--
igor



[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Linux Kernel]     [Linux Kernel Hardening]     [Linux NFS]     [Linux NILFS]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux SCSI]

  Powered by Linux