John Baldwin wrote:
On Wednesday 14 November 2007 05:01:32 am Kris Kennaway wrote:
Julian Elischer wrote:
julian 2007-11-14 05:43:55 UTC
FreeBSD src repository
Modified files:
sys/i386/bios apm.c
Log:
Apply the same sort of locking done in
sys/dev/acpica/acpi.c rev 1.196 a while ago:
Grab Giant around calls to DEVICE_SUSPEND/RESUME in
acpi_SetSleepState().
If we are resuming non-MPSAFE drivers, they need Giant held for them.
This may fix some obscure suspend/resume problems. It has fixed keyrate
setting problems that were triggered by cardbus (MPSAFE) changing the
ordering for syscons resume (non-MPSAFE). Also, add some asserts that
Giant is held in our suspend/resume and shutdown methods.
Submitted by: Marko Zec
Revision Changes Path
1.149 +10 -0 src/sys/i386/bios/apm.c
Why are we adding new unconditional giant acquisitions to the tree?
Devices indicate whether or not they are mpsafe, why can't this be made
conditional?
Actually, we have no way in new-bus to mark new-bus operations like bus
enumeration, etc. MPSAFE, and much of it is not (e.g.
attach/detach/suspend/resume, etc. functions). Additionally, making this
conditional would require a scheme where you acquire Giant when you walk down
the tree into a non-MPSAFE driver which would add complication to many (if
not all) bus drivers. Considering the rarity of suspend/resume (not a
critical-path) the overhead of adding all that may not be worth it. At some
point when we do have locking for all device driver operations this can be
removed, but it won't really hurt anything to leave it as it is for now.
OK thanks for the explanation.
Kris
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