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

From: Andi Kleen
Date: Fri Mar 22 2013 - 21:31:18 EST

From: Andi Kleen <ak@xxxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxxx>
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];
+ unsigned notxn; /* transactions are disabled */
unsigned int sig_on_uaccess_error:1;
unsigned int uaccess_err:1; /* uaccess failed */
@@ -279,6 +280,13 @@ static inline bool is_ia32_task(void)
return false;
+#define txn_disabled() (current_thread_info()->notxn)
+#define disable_txn() (current_thread_info()->notxn++)
+#define reenable_txn() (current_thread_info()->notxn--)
#endif /* !__ASSEMBLY__ */

#ifndef __ASSEMBLY__

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