Fixing: Drone CAN Crashdump on boot #269
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the AP_CANManager::log_text() gets called from debug logging in AP_DroneCAN. It is a method on a common AP_CANManager object which is shared by multiple AP_DroneCAN threads. if two threads call the debug log messages at the same time then we can end up with _log_pos greater than LOG_BUFFER_SIZE (1024) and overwrite past the end of the buffer in the crash_dump we have for this case the next piece of memory was hal.can[0], and the overwrite of the buffer had corrupted the MessageRam_ structurre in the ChibiOS CAN interface code. That led to a hardfault on receive of a CAN message Note that this issue only happens if CAN_LOGLEVEL is set to greater than zero, and the default is zero. So users can avoid the bug by checking they have not changed CAN_LOGLEVEL. Also, this is likely an issue that only happens on startup, as once the two AP_DroneCAN threads are fully running they have the same thread priority so can't pre-empt each other. During startup some messages are sent from the main thread which has a different priority to the AP_DroneCAN threads, and can thus trigger this issue
To expand on this, this parameter does not add anything extra to our logs. It adds a textfile to @sys which can be manually downloaded over MAVFTP and then reviewed. If we ever need to do some kind of debugging like that, we can just enable the parameter. |
robertlong13
approved these changes
Dec 14, 2024
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Cherry picking PR: ArduPilot/ardupilot#28859
Also, removing the CAN_LOGLEVEL from default which was set to 4 - LOG-ALL to now autopilot default which is None.
As this anyway doesn't give any helpful information for us to use/troubleshoot.