Author: mjg Date: Sat Nov 30 16:46:19 2019 New Revision: 355228 URL: https://svnweb.freebsd.org/changeset/base/355228
Log: devfs: introduce a per-dev lock to protect ->si_devsw This allows bumping threadcount without taking the global devmtx lock. In particular this eliminates contention on said lock while using bhyve with multiple vms. Reviewed by: kib Tested by: markj MFC after: 2 weeks Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D22548 Modified: head/sys/fs/devfs/devfs_devs.c head/sys/fs/devfs/devfs_int.h head/sys/kern/kern_conf.c head/sys/kern/subr_witness.c Modified: head/sys/fs/devfs/devfs_devs.c ============================================================================== --- head/sys/fs/devfs/devfs_devs.c Sat Nov 30 16:41:47 2019 (r355227) +++ head/sys/fs/devfs/devfs_devs.c Sat Nov 30 16:46:19 2019 (r355228) @@ -138,6 +138,8 @@ devfs_alloc(int flags) if (cdp == NULL) return (NULL); + mtx_init(&cdp->cdp_threadlock, "devthrd", NULL, MTX_DEF); + cdp->cdp_dirents = &cdp->cdp_dirent0; cdev = &cdp->cdp_c; @@ -180,6 +182,7 @@ devfs_free(struct cdev *cdev) devfs_free_cdp_inode(cdp->cdp_inode); if (cdp->cdp_maxdirent > 0) free(cdp->cdp_dirents, M_DEVFS2); + mtx_destroy(&cdp->cdp_threadlock); free(cdp, M_CDEVP); } Modified: head/sys/fs/devfs/devfs_int.h ============================================================================== --- head/sys/fs/devfs/devfs_int.h Sat Nov 30 16:41:47 2019 (r355227) +++ head/sys/fs/devfs/devfs_int.h Sat Nov 30 16:46:19 2019 (r355228) @@ -70,6 +70,8 @@ struct cdev_priv { void *cdp_dtr_cb_arg; LIST_HEAD(, cdev_privdata) cdp_fdpriv; + + struct mtx cdp_threadlock; }; #define cdev2priv(c) __containerof(c, struct cdev_priv, cdp_c) Modified: head/sys/kern/kern_conf.c ============================================================================== --- head/sys/kern/kern_conf.c Sat Nov 30 16:41:47 2019 (r355227) +++ head/sys/kern/kern_conf.c Sat Nov 30 16:46:19 2019 (r355228) @@ -186,16 +186,16 @@ dev_refthread(struct cdev *dev, int *ref) *ref = 0; return (dev->si_devsw); } - dev_lock(); + cdp = cdev2priv(dev); + mtx_lock(&cdp->cdp_threadlock); csw = dev->si_devsw; if (csw != NULL) { - cdp = cdev2priv(dev); if ((cdp->cdp_flags & CDP_SCHED_DTR) == 0) atomic_add_long(&dev->si_threadcount, 1); else csw = NULL; } - dev_unlock(); + mtx_unlock(&cdp->cdp_threadlock); if (csw != NULL) *ref = 1; return (csw); @@ -223,19 +223,21 @@ devvn_refthread(struct vnode *vp, struct cdev **devp, } csw = NULL; - dev_lock(); + VI_LOCK(vp); dev = vp->v_rdev; if (dev == NULL) { - dev_unlock(); + VI_UNLOCK(vp); return (NULL); } cdp = cdev2priv(dev); + mtx_lock(&cdp->cdp_threadlock); if ((cdp->cdp_flags & CDP_SCHED_DTR) == 0) { csw = dev->si_devsw; if (csw != NULL) atomic_add_long(&dev->si_threadcount, 1); } - dev_unlock(); + mtx_unlock(&cdp->cdp_threadlock); + VI_UNLOCK(vp); if (csw != NULL) { *devp = dev; *ref = 1; @@ -1136,20 +1138,26 @@ destroy_devl(struct cdev *dev) dev->si_flags &= ~SI_CLONELIST; } + mtx_lock(&cdp->cdp_threadlock); csw = dev->si_devsw; dev->si_devsw = NULL; /* already NULL for SI_ALIAS */ while (csw != NULL && csw->d_purge != NULL && dev->si_threadcount) { csw->d_purge(dev); + mtx_unlock(&cdp->cdp_threadlock); msleep(csw, &devmtx, PRIBIO, "devprg", hz/10); + mtx_lock(&cdp->cdp_threadlock); if (dev->si_threadcount) printf("Still %lu threads in %s\n", dev->si_threadcount, devtoname(dev)); } while (dev->si_threadcount != 0) { /* Use unique dummy wait ident */ + mtx_unlock(&cdp->cdp_threadlock); msleep(&csw, &devmtx, PRIBIO, "devdrn", hz / 10); + mtx_lock(&cdp->cdp_threadlock); } + mtx_unlock(&cdp->cdp_threadlock); dev_unlock(); if ((cdp->cdp_flags & CDP_UNREF_DTR) == 0) { /* avoid out of order notify events */ Modified: head/sys/kern/subr_witness.c ============================================================================== --- head/sys/kern/subr_witness.c Sat Nov 30 16:41:47 2019 (r355227) +++ head/sys/kern/subr_witness.c Sat Nov 30 16:46:19 2019 (r355228) @@ -602,6 +602,7 @@ static struct witness_order_list_entry order_lists[] = { "vm map (system)", &lock_class_mtx_sleep }, { "vnode interlock", &lock_class_mtx_sleep }, { "cdev", &lock_class_mtx_sleep }, + { "devthrd", &lock_class_mtx_sleep }, { NULL, NULL }, /* * VM _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
