printk in init_module mixing with printf in insmod
I recently upgraded my ppc405 embedded system
from 2.4.2 or so to 2.4.17 or so. I use modutils-2.4.12. When I insert a nongpl module,
the
fprintf(stderr, "Warning: loading foo.o will taint kernel\n");
in insmod and the
printk("Hello, world\n");
in the module are intermixed unpleasantly, yielding output like
Warning: loHello,ading foo.o world
will taint kernel
This garbled output makes reading the debugging printk's difficult.
I suppose this isn't terribly important, since printk's are kind of a no-no in production, and this only affects printk's in init_module, but it'd be nice to know what
the cleanest way to get rid of the mixing is. Adding a sleep inside insmod seems heavyhanded. I suppose I could redirect insmod's output to a file, sleep a bit, and then display the file... bleah.
- Dan
Quoted 7 lines · Dan Kegel
I suppose this isn't terribly important, since printk's are kind of a no-no in production, and this only affects printk's in
init_module, but it'd be nice to know what
the cleanest way to get rid of the mixing is. Adding a sleep inside insmod seems heavyhanded. I suppose I could redirect insmod's output to a file, sleep a bit, and then display the file... bleah.
Output from a program to a serial port is buffered, and is thus asynchronous to the program. printk output is synchronous, and as such will interrupt the normal IO to the port.
If you're going to use delays, you need to take account of the serial port baud rate and adjust the delay accordingly. However, you don't really know how many characters are pending in the kernel anyway.
I don't think there's an answer to this if you're going to run both applications and kernel console on the same port.
Signature · 2 lines
Russell King ([email protected]) The developer of ARM Linux http://www.arm.linux.org.uk/personal/aboutme.html
Quoted 10 lines · Russell King
Quoted 7 lines · Dan Kegel
I suppose this isn't terribly important, since printk's are kind of a no-no in production, and this only affects printk's in
init_module, but it'd be nice to know what
the cleanest way to get rid of the mixing is. Adding a sleep inside insmod seems heavyhanded. I suppose I could redirect insmod's output to a file, sleep a bit, and then display the file... bleah.
Quoted 7 lines
Output from a program to a serial port is buffered, and is thus asynchronous to the program. printk output is synchronous, and as such will interrupt the normal IO to the port.
If you're going to use delays, you need to take account of the serial port baud rate and adjust the delay accordingly. However, you don't really know how many characters are pending in the kernel anyway.
Thanks for the info.
For now, I'm just kludging in a sleep(1) in insmod right after the print, as a temporary fix for my particular needs. Saves me editing lots of source files, and it "works" for this particular situation.
Quoted 2 lines
I don't think there's an answer to this if you're going to run both applications and kernel console on the same port.
insmod is run by /etc/init.d/rcS, so it's kind of unavoidable. But I'm happy with my little private kludge for now.
- Dan
Quoted 7 lines
printk("Hello, world\n");
in the module are intermixed unpleasantly, yielding output like
Warning: loHello,ading foo.o world
will taint kernelThis garbled output makes reading the debugging printk's difficult.
Quoted 7 lines
I suppose this isn't terribly important, since printk's are kind of a no-no in production, and this only affects printk's in
init_module, but it'd be nice to know what
the cleanest way to get rid of the mixing is. Adding a sleep inside insmod seems heavyhanded. I suppose I could redirect insmod's output to a file, sleep a bit, and then display the file... bleah.
Probably you want to fprintf the message after the module initialise has reported completion, instead of before. I see no good way of hiding it the other way around.