Re: [PATCH 12/29] x86, tsx: Add a per thread transaction disable count

Borislav Petkov
2013-03-23T11:51:22Z

On Fri, Mar 22, 2013 at 06:25:06PM -0700, Andi Kleen wrote:
> From: Andi Kleen <ak@linux.intel.com>
>
> For some locks that have a low chance of not aborting it's
> best to just disable transactions.
>
> Add a counter to thread_info to allow to disable tranasctions
> for the current task.
>
> I originally experimented with more complicated solutions,
> like a magic spinlock type to disable with magic type matching,
> but that was very intrusive in the locking code.
>
> This setup -- while adding a few more instructions -- is more
> flexible and seems to work quite nicely.
>
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> ---
> arch/x86/include/asm/thread_info.h | 8 ++++++++
> 1 files changed, 8 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
> index 2cd056e..91bb84e 100644
> --- a/arch/x86/include/asm/thread_info.h
> +++ b/arch/x86/include/asm/thread_info.h
> @@ -39,6 +39,7 @@ struct thread_info {
> */
> __u8 supervisor_stack[0];
> #endif
> + unsigned notxn; /* transactions are disabled */

This surely can be a bitfield like the other two below. It is basically
begging to be one.

> unsigned int sig_on_uaccess_error:1;
> unsigned int uaccess_err:1; /* uaccess failed */
> };

--
Regards/Gruss,
Boris.

Sent from a fat crate under my desk. Formatting is fine.
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