Package: linux-image-686-pae
Version: 3.2+46
On current Debian kernels the the WCHAN column for procps is NOT working.
Run this command:
# cat /proc/*/wchan
For current Debian kernels you get all zeros, you should get something
like:
devtmpfsdsys_pauserescuer_threadbdi_sync_superskjournald2rescuer_threadhub_threadrescuer_threadrescuer_threadrescuer_threadscsi_error_handlerscsi_error_handlerscsi_error_handlerscsi_error_handlerscsi_
etc etc.
This is all due to the configuration of the frame pointers, there are two
confgurations that work, the current release format isn't one of them...
Current setting -- not working:
CONFIG_SCHED_OMIT_FRAME_POINTER=y
CONFIG_ARCH_WANT_FRAME_POINTERS=y
# CONFIG_FRAME_POINTER is not set
Working setting without frame pointers (except sched.o):
# CONFIG_SCHED_OMIT_FRAME_POINTER is not set
CONFIG_ARCH_WANT_FRAME_POINTERS=y
# CONFIG_FRAME_POINTER is not set
Working setting with frame pointers (Ubuntu):
CONFIG_SCHED_OMIT_FRAME_POINTER=y
CONFIG_ARCH_WANT_FRAME_POINTERS=y
CONFIG_FRAME_POINTER=y
The the "with frame pointers" method (like Ubuntu) gives more detailed
information than "without frame pointers", but for me both are reasonable.
The CONFIG_SCHED_OMIT_FRAME_POINTER option is rather confusing, it only
changes the compile options if it's NOT set. If it's set the frame pointer
option says what we get. If it's not set an extra "no-omit-frame-pointer"
is added to the compile of kernel/sched.c; so if the kernel is compiled
with frame pointers it has no effect.
Note: This only applies to x86 and amd64; the "not working" combination
where ALL frame pointers are omitted works fine on some processors,
especially if it's impossible to remove the frame pointers anyway.
IIRC: ARM needs frame pointers, Spark always has frame pointers.
--
Rob. (Robert de Bath <robert$ @ debath.co.uk>)
<http://www.debath.co.uk/>
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