Date: Tue, 20 Jan 2015 21:15:34 +0000 (UTC) From: Will Andrews <will@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r277440 - head/sys/cam Message-ID: <201501202115.t0KLFYZ2036130@svn.freebsd.org>
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Author: will Date: Tue Jan 20 21:15:33 2015 New Revision: 277440 URL: https://svnweb.freebsd.org/changeset/base/277440 Log: 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. Discussed with: ken, mav (in general) MFC after: 1 week Sponsored by: Spectra Logic Modified: head/sys/cam/cam_xpt.c Modified: head/sys/cam/cam_xpt.c ============================================================================== --- head/sys/cam/cam_xpt.c Tue Jan 20 21:09:39 2015 (r277439) +++ head/sys/cam/cam_xpt.c Tue Jan 20 21:15:33 2015 (r277440) @@ -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; @@ -151,6 +153,8 @@ static struct xpt_softc xsoftc; 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; @@ -976,6 +980,7 @@ 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); @@ -992,6 +997,7 @@ 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); } }
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