SMP General TODO List
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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.
Subsystem |
Dependencies |
Owner |
Some TTY drivers override the per-TTY mutex: syscons (Giant), si (Giant), nmdm and usb_serial |
|
ed |
syscons is not MPSAFE |
|
ed |
Some CAM SCSI drivers are not mpsafe (XXX need list) |
|
|
KAME IPv6 ND6 and MLD6 are not MPSAFE. More details on IPv6/ToDo. |
|
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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. mem) |
|
(maybe) ed |
Giant is still acquired at some points in VM |
swap handling, MPSAFE VFS |
alc |
Giant is still acquired in System V SHM |
|
wkoszek |
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 |
|
rwatson |
The netncp and netsmb code unconditionally acquire Giant |
|
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ALTQ uses non-mpsafe callouts |
|
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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 |
|
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Module event handlers run under Giant |
|
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Linux compat ioctl() handlers |
|
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start_init() |
|
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SYSINIT() routines |
|
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ntp system calls and settime() |
|
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reboot() |
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Excluded from this list are a large number of post-SMPng optimization tasks relating to scheduling, locking strategy, etc, that are described elsewhere.