SMP General TODO List
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.
Subsystem |
Dependencies |
Owner |
TTYs are not MPSAFE |
|
ed |
TTY consumers in the network stack are not MPSAFE (PPP, SLIP, ng_tty,...) |
TTYs |
rwatson |
Some CAM SCSI drivers are not mpsafe (XXX need list) |
|
|
Newbus is not MPSAFE |
|
scottl,imp |
USB is not MPSAFE |
|
hps |
KAME IPv6 ND6 and MLD6 are not MPSAFE |
|
|
Network address lists are insufficiently locked |
|
rwatson |
Many pseudo-devices are not yet marked as MPSAFE, even though many are in fact MPSAFE. (i.e. io, mem, ctty) |
|
|
Giant is unconditionally acquired before entering VFS via UNIX domain sockets, but doesn't need to be |
|
wkoszek |
Giant is still acquired at some points in VM |
|
alc |
Giant is still acquired in System V SHM |
|
wkoszek |
sysctls are Giant-locked. csjp and kris have a prototype patch allowing for (and partially implementing) pushdown. |
|
csjp, kris |
When pseudofs is mounted then every process exit acquires two extra mutexes including Giant. See pfs_exit(). This code is also incredibly inefficient. |
|
des |
Some filesystems are not mpsafe. The most important of these is probably msdosfs. Others (that do not set MNTK_MPSAFE as mount flag): cd9660, deadfs, fdescfs, hpfs, ntfs, nwfs, procfs, smbfs, udf, coda, fifofs, portalfs, unionfs. |
|
lulf(fdescfs) |
Mounting and unmounting of filesystems acquires Giant |
|
|
/dev/mem is marked as requiring Giant but it is unclear why |
|
|
The NFSv4 client code unconditionally acquires Giant |
|
|
The non-MPSAFE timeout() API is used in the following kernel systems: ipfilter, netgraph/ng_fec.c, if_slowtimo(), various drivers, and speaker beeping |
|
|
netatalk uses the non-MPSAFE timeout() API |
|
rwatson |
The netncp and netsmb code unconditionally acquire Giant |
|
|
kern/subr_log.c is not mpsafe |
TTY? |
|
ALTQ uses non-mpsafe callouts |
|
|
The following drivers use non-mpsafe callouts: dev/mpt/mpt_raid.c dev/dcons/dcons_os.c dev/esp/ncr53c9x.c dev/kbdmux/kbdmux.c dev/lmc/if_lmc.c dev/nmdm/nmdm.c dev/rc/rc.c dev/uart/uart_kbd_sun.c |
TTY(dcons) |
|
The following network drivers are not mpsafe: an arl awi cnw ce cp cs ctau cx en ex fe hfa idt ie if_ic oltr mn pcf pdq ppbus ray sbni sbsh snc sr tx wl xe. They are threatened with removal in 7.0. |
|
rwatson (danish axe) |
These drivers are not mpsafe: ichsmb, ipmi, intpm |
|
|
Excluded from this list are a large number of post-SMPng optimization tasks relating to scheduling, locking strategy, etc, that are described elsewhere.