From 046a619d8e9746fa4c0e29e8c6b78e16efc008a8 Mon Sep 17 00:00:00 2001 From: Jason Low Date: Mon, 14 Jul 2014 10:27:48 -0700 Subject: locking/spinlocks/mcs: Rename optimistic_spin_queue() to optimistic_spin_node() Currently, the per-cpu nodes structure for the cancellable MCS spinlock is named "optimistic_spin_queue". However, in a follow up patch in the series we will be introducing a new structure that serves as the new "handle" for the lock. It would make more sense if that structure is named "optimistic_spin_queue". Additionally, since the current use of the "optimistic_spin_queue" structure are "nodes", it might be better if we rename them to "node" anyway. This preparatory patch renames all current "optimistic_spin_queue" to "optimistic_spin_node". Signed-off-by: Jason Low Signed-off-by: Peter Zijlstra Cc: Scott Norton Cc: "Paul E. McKenney" Cc: Dave Chinner Cc: Waiman Long Cc: Davidlohr Bueso Cc: Rik van Riel Cc: Andrew Morton Cc: "H. Peter Anvin" Cc: Steven Rostedt Cc: Tim Chen Cc: Konrad Rzeszutek Wilk Cc: Aswin Chandramouleeswaran Cc: Linus Torvalds Cc: Chris Mason Cc: Heiko Carstens Cc: Josef Bacik Link: http://lkml.kernel.org/r/1405358872-3732-2-git-send-email-jason.low2@hp.com Signed-off-by: Ingo Molnar --- include/linux/mutex.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/linux/mutex.h') diff --git a/include/linux/mutex.h b/include/linux/mutex.h index 11692dea18aa..885f3f56a77f 100644 --- a/include/linux/mutex.h +++ b/include/linux/mutex.h @@ -46,7 +46,7 @@ * - detects multi-task circular deadlocks and prints out all affected * locks and tasks (and only those tasks) */ -struct optimistic_spin_queue; +struct optimistic_spin_node; struct mutex { /* 1: unlocked, 0: locked, negative: locked, possible waiters */ atomic_t count; @@ -56,7 +56,7 @@ struct mutex { struct task_struct *owner; #endif #ifdef CONFIG_MUTEX_SPIN_ON_OWNER - struct optimistic_spin_queue *osq; /* Spinner MCS lock */ + struct optimistic_spin_node *osq; /* Spinner MCS lock */ #endif #ifdef CONFIG_DEBUG_MUTEXES const char *name; -- cgit v1.2.2 From 90631822c5d307b5410500806e8ac3e63928aa3e Mon Sep 17 00:00:00 2001 From: Jason Low Date: Mon, 14 Jul 2014 10:27:49 -0700 Subject: locking/spinlocks/mcs: Convert osq lock to atomic_t to reduce overhead The cancellable MCS spinlock is currently used to queue threads that are doing optimistic spinning. It uses per-cpu nodes, where a thread obtaining the lock would access and queue the local node corresponding to the CPU that it's running on. Currently, the cancellable MCS lock is implemented by using pointers to these nodes. In this patch, instead of operating on pointers to the per-cpu nodes, we store the CPU numbers in which the per-cpu nodes correspond to in atomic_t. A similar concept is used with the qspinlock. By operating on the CPU # of the nodes using atomic_t instead of pointers to those nodes, this can reduce the overhead of the cancellable MCS spinlock by 32 bits (on 64 bit systems). Signed-off-by: Jason Low Signed-off-by: Peter Zijlstra Cc: Scott Norton Cc: "Paul E. McKenney" Cc: Dave Chinner Cc: Waiman Long Cc: Davidlohr Bueso Cc: Rik van Riel Cc: Andrew Morton Cc: "H. Peter Anvin" Cc: Steven Rostedt Cc: Tim Chen Cc: Konrad Rzeszutek Wilk Cc: Aswin Chandramouleeswaran Cc: Linus Torvalds Cc: Chris Mason Cc: Heiko Carstens Cc: Josef Bacik Link: http://lkml.kernel.org/r/1405358872-3732-3-git-send-email-jason.low2@hp.com Signed-off-by: Ingo Molnar --- include/linux/mutex.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include/linux/mutex.h') diff --git a/include/linux/mutex.h b/include/linux/mutex.h index 885f3f56a77f..42aa9b9ecd5f 100644 --- a/include/linux/mutex.h +++ b/include/linux/mutex.h @@ -17,6 +17,7 @@ #include #include #include +#include /* * Simple, straightforward mutexes with strict semantics: @@ -46,7 +47,6 @@ * - detects multi-task circular deadlocks and prints out all affected * locks and tasks (and only those tasks) */ -struct optimistic_spin_node; struct mutex { /* 1: unlocked, 0: locked, negative: locked, possible waiters */ atomic_t count; @@ -56,7 +56,7 @@ struct mutex { struct task_struct *owner; #endif #ifdef CONFIG_MUTEX_SPIN_ON_OWNER - struct optimistic_spin_node *osq; /* Spinner MCS lock */ + struct optimistic_spin_queue osq; /* Spinner MCS lock */ #endif #ifdef CONFIG_DEBUG_MUTEXES const char *name; -- cgit v1.2.2