SMP General TODO List

/!\ This page was last edited in late 2012. Surely it needs an update.

This page lists some general locking/basic SMP todo items that have thus far slipped through the cracks; some are more relevant to the real world than others. For these purposes, we consider a component to be not MPSAFE if it either entirely relies on the Giant lock to operate correctly, or if its required dependencies rely on the Giant lock to operate correctly. Depending on the subsystem, the impact may be significant or limited with respect to other components simultaneously operating in the kernel. Some have owners, some don't.




Some TTY drivers override the per-TTY mutex: syscons (Giant), si (Giant), nmdm and usb_serial


syscons is not MPSAFE


Some CAM SCSI drivers are not mpsafe (XXX need list)

KAME IPv6 ND6 and MLD6 are not MPSAFE. More details on IPv6TODO.

Network address lists are insufficiently locked


Many pseudo-devices are not yet marked as MPSAFE, even though many are in fact MPSAFE. (i.e. mem)

(maybe) ed

Giant is still acquired at some points in VM

swap handling, MPSAFE VFS


Giant is still acquired in System V SHM


Some filesystems are not mpsafe. These are (that do not set MNTK_MPSAFE as mount flag): hpfs, ntfs, nwfs, smbfs, coda, portalfs.

Mounting and unmounting of filesystems acquires Giant

The non-MPSAFE timeout() API is used in the following kernel systems: acpi, scsi_low, ipfilter, advansys, amr, atkbdc, sbp, hptmv, hptrr, iir, ips, isp, mcd, mly, mn, scd, syscons, twa, sysbeep, if_slowtimo, netatalk, ng_btsocket, ng_fec, netipsec, netncp, ncr

netatalk uses the non-MPSAFE timeout() API


The netncp and netsmb code unconditionally acquire Giant

ALTQ uses non-mpsafe callouts

The following drivers use non-mpsafe callouts: dev/mpt/mpt_raid.c dev/esp/ncr53c9x.c dev/kbdmux/kbdmux.c dev/lmc/if_lmc.c dev/rc/rc.c dev/uart/uart_kbd_sun.c

Module event handlers run under Giant

linux_getcwd_common() (should use LK_SHARED and MPSAFEVFS)

Linux compat ioctl() handlers

SVR4 compat streams


SYSINIT() routines

ntp system calls and settime()


Excluded from this list are a large number of post-SMPng optimization tasks relating to scheduling, locking strategy, etc, that are described elsewhere.

SMPTODO (last edited 2015-10-18 04:48:21 by MarkLinimon)