pipe: allow for lockless pipe_stat

pipes get stated all thet time and this avoidably contributed to contention.
The pipe lock is only held to accomodate MAC and to check the type.

Since normally there is no probe for pipe stat depessimize this by having the
flag.

The pipe_state field gets modified with locks held all the time and it's not
feasible to convert them to use atomic store. Move the type flag away to a
separate variable as a simple cleanup and to provide stable field to read.
Use short for both fields to avoid growing the struct.

While here short-circuit MAC for pipe_poll as well.

1 files changed, 7 insertions, 2 deletions

diff --git a/sys/sys/pipe.h b/sys/sys/pipe.h
index 2f1568ab6637..8bdfae8b2308 100644
--- a/sys/sys/pipe.h
+++ b/sys/sys/pipe.h
@@ -95,7 +95,11 @@ struct pipemapping {
 #define PIPE_LWANT	0x200	/* Process wants exclusive access to pointers/data. */
 #define PIPE_DIRECTW	0x400	/* Pipe direct write active. */
 #define PIPE_DIRECTOK	0x800	/* Direct mode ok. */
-#define PIPE_NAMED	0x1000	/* Is a named pipe. */
+
+/*
+ * Bits in pipe_type.
+ */
+#define PIPE_TYPE_NAMED	0x001	/* Is a named pipe. */
 
 /*
  * Per-pipe data structure.
@@ -111,7 +115,8 @@ struct pipe {
 	struct	sigio *pipe_sigio;	/* information for async I/O */
 	struct	pipe *pipe_peer;	/* link with other direction */
 	struct	pipepair *pipe_pair;	/* container structure pointer */
-	u_int	pipe_state;		/* pipe status info */
+	u_short	pipe_state;		/* pipe status info */
+	u_short	pipe_type;		/* pipe type info */
 	int	pipe_busy;		/* busy flag, mostly to handle rundown sanely */
 	int	pipe_present;		/* still present? */
 	int	pipe_wgen;		/* writer generation for named pipe */