Date: Sat, 23 Nov 2019 23:43:52 +0000 (UTC) From: Warner Losh <imp@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r355037 - head/sys/dev/pci Message-ID: <201911232343.xANNhqkQ097797@repo.freebsd.org>
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Author: imp Date: Sat Nov 23 23:43:52 2019 New Revision: 355037 URL: https://svnweb.freebsd.org/changeset/base/355037 Log: Push Giant down one layer The /dev/pci device doesn't need GIANT, per se. However, one routine that it calls, pci_find_dbsf implicitly does. It walks a list that can change when PCI scans a new bus. With hotplug, this means we could have a race with that scanning. To prevent that, take out Giant around scanning the list. However, given that we have places in the tree that drop giant, if held when we call into them, the whole use of Giant to protect newbus may be less effective that we desire, so add a comment about why we're talking it out, and we'll address the issue when we lock newbus with something other than Giant. Modified: head/sys/dev/pci/pci.c head/sys/dev/pci/pci_user.c Modified: head/sys/dev/pci/pci.c ============================================================================== --- head/sys/dev/pci/pci.c Sat Nov 23 23:41:21 2019 (r355036) +++ head/sys/dev/pci/pci.c Sat Nov 23 23:43:52 2019 (r355037) @@ -445,18 +445,21 @@ pci_find_bsf(uint8_t bus, uint8_t slot, uint8_t func) device_t pci_find_dbsf(uint32_t domain, uint8_t bus, uint8_t slot, uint8_t func) { - struct pci_devinfo *dinfo; + struct pci_devinfo *dinfo = NULL; + /* Giant because newbus is Giant locked revisit with newbus locking */ + mtx_lock(&Giant); STAILQ_FOREACH(dinfo, &pci_devq, pci_links) { if ((dinfo->cfg.domain == domain) && (dinfo->cfg.bus == bus) && (dinfo->cfg.slot == slot) && (dinfo->cfg.func == func)) { - return (dinfo->cfg.dev); + break; } } + mtx_unlock(&Giant); - return (NULL); + return (dinfo != NULL ? dinfo->cfg.dev : NULL); } /* Find a device_t by vendor/device ID */ Modified: head/sys/dev/pci/pci_user.c ============================================================================== --- head/sys/dev/pci/pci_user.c Sat Nov 23 23:41:21 2019 (r355036) +++ head/sys/dev/pci/pci_user.c Sat Nov 23 23:43:52 2019 (r355037) @@ -119,7 +119,7 @@ static d_ioctl_t pci_ioctl; struct cdevsw pcicdev = { .d_version = D_VERSION, - .d_flags = D_NEEDGIANT, + .d_flags = 0, .d_open = pci_open, .d_close = pci_close, .d_ioctl = pci_ioctl,
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