svn commit: r288695 - stable/10/sys/cam

[Alexander Motin]

Author: mav
Date: Mon Oct  5 07:10:09 2015
New Revision: 288695
URL: https://svnweb.freebsd.org/changeset/base/288695

Log:
  MFC r277440 (by will):
  Restore the CAM XPT peripheral generation counter, and export it via sysctl.
  
  Define it as an atomic uint32_t.  These increments happen infrequently
  enough for the atomic overhead to be a problem, and since they're now
  independent atomics, they won't contend with xpt_lock_buses().
  
  This counter is useful as a means of cheaply identifying whether any changes
  have been made to the CAM peripheral list.  Userland programs have no guarantee
  that the counter won't change on them while being returned or while processing
  the information, so they must be written accordingly.

Modified:
  stable/10/sys/cam/cam_xpt.c
Directory Properties:
  stable/10/   (props changed)

Modified: stable/10/sys/cam/cam_xpt.c
==============================================================================
--- stable/10/sys/cam/cam_xpt.c	Mon Oct  5 07:07:37 2015	(r288694)
+++ stable/10/sys/cam/cam_xpt.c	Mon Oct  5 07:10:09 2015	(r288695)
@@ -93,6 +93,8 @@ struct xpt_task {
 };
 
 struct xpt_softc {
+	uint32_t		xpt_generation;
+
 	/* number of high powered commands that can go through right now */
 	struct mtx		xpt_highpower_lock;
 	STAILQ_HEAD(highpowerlist, cam_ed)	highpowerq;
@@ -154,6 +156,8 @@ MTX_SYSINIT(xpt_topo_init, &xsoftc.xpt_t
 TUNABLE_INT("kern.cam.boot_delay", &xsoftc.boot_delay);
 SYSCTL_INT(_kern_cam, OID_AUTO, boot_delay, CTLFLAG_RDTUN,
            &xsoftc.boot_delay, 0, "Bus registration wait time");
+SYSCTL_UINT(_kern_cam, OID_AUTO, xpt_generation, CTLFLAG_RD,
+	    &xsoftc.xpt_generation, 0, "CAM peripheral generation count");
 
 struct cam_doneq {
 	struct mtx_padalign	cam_doneq_mtx;
@@ -981,6 +985,7 @@ xpt_add_periph(struct cam_periph *periph
 		device->generation++;
 		SLIST_INSERT_HEAD(&device->periphs, periph, periph_links);
 		mtx_unlock(&device->target->bus->eb_mtx);
+		atomic_add_32(&xsoftc.xpt_generation, 1);
 	}
 
 	return (status);
@@ -997,6 +1002,7 @@ xpt_remove_periph(struct cam_periph *per
 		device->generation++;
 		SLIST_REMOVE(&device->periphs, periph, cam_periph, periph_links);
 		mtx_unlock(&device->target->bus->eb_mtx);
+		atomic_add_32(&xsoftc.xpt_generation, 1);
 	}
 }