On 04/24/2012 02:57 PM, Gilles Chanteperdrix wrote: > On 04/24/2012 08:47 PM, Andrew Tannenbaum wrote: >> I'm running >> >> Linux 2.6.38.8 >> Xenomai 2.6.0 >> Atom N270 CPU >> >> I'm talking to CAN with a PEAK PCI SJA1000 CAN adapter. >> >> I have a control loop running at 200 Hz, and I use it to drive a motor >> and read an encoder using rtcan. My code is based on the >> rtcansend/rtcanrecv examples. >> >> I found a bug where my control loop was hanging, and I've isolated the >> problem so that it may be reproduced with Xenomai supplied tools, >> without using my own code. >> >> The problem is: >> >> When I have a loop that is sending CAN packets, if I read >> /proc/rtcan/rtcan0/registers at the same time, it causes the loop to >> hang. The hang is in rt_dev_sendto. >> >> To reproduce: >> >> Configure the CAN controller >> >> $ rtcanconfig rtcan0 --baudrate=1000000 start >> >> Send packets, in this case, SYNC messages at 1000 Hz >> with tty output 1 Hz. >> >> $ rtcansend rtcan0 -i 0x80 -p 1000 -l 1000000 >> >> It will print CAN SYNC (0x80) messages: >> >> <0x080> [0] >> <0x080> [0] >> ... >> >> In another window, read rtcan0/registers in a loop (10 Hz): >> >> $ while :; do cat /proc/rtcan/rtcan0/registers; sleep .1; done > > Hi Andrew, > > I am probably not the one which will answer your question, because I > know nothing about CAN hardware. What I know however is that some > hardware registers, when read, have side effects. For instance reading > an interrupt status may deassert the hardware interrupt. > > The code for /proc/rtcan/rtcan0/registers is compiled if > CONFIG_XENO_DRIVERS_CAN_DEBUG is #defined. > > This would seem to indicate that perhaps some registers have side > effects, and so this /proc file more a debug tool than something which > should be used on a regular basis. > > Regards. >
Thanks, Gilles, I see. It seems that the registers are the only member of /proc/rtcan that is #ifdef CONFIG_XENO_DRIVERS_CAN_DEBUG so it looks like the rest should be safe. _______________________________________________ Xenomai-help mailing list [email protected] https://mail.gna.org/listinfo/xenomai-help
