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Subject[(RT RFC) PATCH v2 2/9] sysctl for runtime-control of lateral mutex stealing
Date
From: Sven-Thorsten Dietrich <sdietrich@suse.de>

Add /proc/sys/kernel/lateral_steal, to allow switching on and off
equal-priority mutex stealing between threads.

Signed-off-by: Sven-Thorsten Dietrich <sdietrich@suse.de>
---
kernel/rtmutex.c | 7 ++++++-
kernel/sysctl.c | 14 ++++++++++++++
2 files changed, 20 insertions(+), 1 deletions(-)
diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c
index 6624c66..cd39c26 100644
--- a/kernel/rtmutex.c
+++ b/kernel/rtmutex.c
@@ -18,6 +18,10 @@

#include "rtmutex_common.h"

+#ifdef CONFIG_RTLOCK_LATERAL_STEAL
+int rtmutex_lateral_steal __read_mostly = 1;
+#endif
+
/*
* lock->owner state tracking:
*
@@ -321,7 +325,8 @@ static inline int lock_is_stealable(struct task_struct *pendowner, int unfair)
if (current->prio > pendowner->prio)
return 0;

- if (!unfair && (current->prio == pendowner->prio))
+ if (unlikely(current->prio == pendowner->prio) &&
+ !(unfair && rtmutex_lateral_steal))
#endif
return 0;

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index c913d48..c24c53d 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -175,6 +175,10 @@ extern struct ctl_table inotify_table[];
int sysctl_legacy_va_layout;
#endif

+#ifdef CONFIG_RTLOCK_LATERAL_STEAL
+extern int rtmutex_lateral_steal;
+#endif
+
extern int prove_locking;
extern int lock_stat;

@@ -836,6 +840,16 @@ static struct ctl_table kern_table[] = {
.proc_handler = &proc_dointvec,
},
#endif
+#ifdef CONFIG_RTLOCK_LATERAL_STEAL
+ {
+ .ctl_name = CTL_UNNUMBERED,
+ .procname = "rtmutex_lateral_steal",
+ .data = &rtmutex_lateral_steal,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec,
+ },
+#endif
#ifdef CONFIG_PROC_FS
{
.ctl_name = CTL_UNNUMBERED,


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