Fix problem regarding priority inversion when using the concurrency

kit, CK, in the LinuxKPI.

When threads are pinned to a CPU core or when there is only one CPU,
it can happen that a higher priority thread can call the CK
synchronize function while a lower priority thread holds the read
lock. Because the CK's synchronize is a simple wait loop this can lead
to a deadlock situation. To solve this problem use the recently
introduced CK's wait callback function.

When detecting a CK blocking condition figure out the lowest priority
among the blockers and update the calling thread's priority and
yield. If another CPU core is holding the read lock, pin the thread to
the blocked CPU core and update the priority. The calling threads
priority and CPU bindings are restored before return.

If a thread holding a CK read lock is detected to be sleeping, pause()
will be used instead of yield().

MFC after:		1 week
Sponsored by:		Mellanox Technologies

2 files changed, 3 insertions, 3 deletions

diff --git a/sys/compat/linuxkpi/common/include/linux/sched.h b/sys/compat/linuxkpi/common/include/linux/sched.h
index 4de6f9e28238..59900c12ab1d 100644
--- a/sys/compat/linuxkpi/common/include/linux/sched.h
+++ b/sys/compat/linuxkpi/common/include/linux/sched.h
@@ -37,7 +37,7 @@
 #include <sys/sched.h>
 #include <sys/sleepqueue.h>
 
-#include <linux/types.h>
+#include <linux/list.h>
 #include <linux/compat.h>
 #include <linux/completion.h>
 #include <linux/pid.h>
@@ -72,6 +72,8 @@ struct task_struct {
 	unsigned bsd_ioctl_len;
 	struct completion parked;
 	struct completion exited;
+	TAILQ_ENTRY(task_struct) rcu_entry;
+	int rcu_recurse;
 };
 
 #define	current	({ \
diff --git a/sys/compat/linuxkpi/common/include/linux/srcu.h b/sys/compat/linuxkpi/common/include/linux/srcu.h
index 90e2378a858e..f89fc82a8e1e 100644
--- a/sys/compat/linuxkpi/common/include/linux/srcu.h
+++ b/sys/compat/linuxkpi/common/include/linux/srcu.h
@@ -29,9 +29,7 @@
 #ifndef	_LINUX_SRCU_H_
 #define	_LINUX_SRCU_H_
 
-struct srcu_epoch_record;
 struct srcu_struct {
-	struct srcu_epoch_record *ss_epoch_record;
 };
 
 #define	srcu_dereference(ptr,srcu)	((__typeof(*(ptr)) *)(ptr))