FTR, I was too optimistic. The LoadProhibited & IllegalInstruction crashes may be reduced but still are present, also the one in the Console I thought would most probably be caused by the unsynced logging console registry:
0x4014681e is in OvmsConsole::Poll(unsigned int, void*) (/home/balzer/esp/Open-Vehicle-Monitoring-System-3/vehicle/OVMS.V3/main/ovms_console.cpp:226).
221 if (event.type == ALERT_MULTI)
222 {
223 LogBuffers::iterator before = event.multi->begin(), after;
224 while (true)
225 {
226 buffer = *before;
227 len = strlen(buffer);
228 after = before;
229 ++after;
230 if (after == event.multi->end())
On the positive side, crash frequency still is reduced.
I'm investigating if we need to do more about Mongoose, as many crashes still seem to be related to some network reconfiguration event.
The thread safety patch on the mbufs did help a lot (→https://github.com/openvehicles/Open-Vehicle-Monitoring-System-3/issues/120), but we may actually need to move the mutex up to the API level, at least for every function accessing the manager or connection list or a connection's virtual interface.
Crash example on a vtable indirection:
0x4015d82a is in mg_send (/home/balzer/esp/Open-Vehicle-Monitoring-System-3/vehicle/OVMS.V3/components/mongoose/mongoose/mongoose.c:2776).
2771 size_t mg_send(struct mg_connection *nc, const void *buf, int len) {
2772 nc->last_io_time = (time_t) mg_time();
2773 if (nc->flags & MG_F_UDP) {
2774 len = nc->iface->vtable->udp_send(nc, buf, len);
2775 } else {
2776 len = nc->iface->vtable->tcp_send(nc, buf, len);
2777 }
A Mongoose update won't solve this. Mongoose still has no support or plans for thread safety, they explicitly warn about this:
→ https://mongoose.ws/documentation/#connections-and-event-manager
NOTE: Since Mongoose's core is not protected against concurrent accesses, make sure that all
mg_*API functions are called from the same thread or RTOS task
Us ignoring this seems to be the single most problematic concurrency issue remaining.
My current idea to solve this is introducing a `MongooseClient` class that replicates the critical Mongoose API methods wrapped in a mutex lock, and then simply add that as a base class for any component class using the API.
I doubt the calls actually need to be done in the same task, as Cesanta write. If that turns out to be necessary (why would it?), the mutex can be replaced by a callback implementation extending the netmanager's command job queue.
Synchronizing the access implies each API call may need to wait for the netmanager's `mg_mgr_poll()` timeout, which is currently set to 250 ms. If that becomes an issue, we can probably lower the timeout to 100 or even 50 ms without hurting overall performance.
Regards,
Michael
Am 14.01.26 um 18:22 schrieb Michael Balzer via OvmsDev:
I hope I'm not too optimistic, but from the crash records it seems I've fixed about 50-60% of the crashes with the console registry mutex (https://github.com/openvehicles/Open-Vehicle-Monitoring-System-3/commit/069632f48ef653601b4525201bd0af09a4625208).
This has been added in edge build 3.3.005-615-gd132bfe0, which has now been running in vehicles for two days, with not a single LoadProhibited or IllegalInstruction crash since, and not a single crash in OVMS Console.
Remaining crashes are all abort()s, with about 11% happening from detected heap corruption and the rest from the task watchdog. Crash signatures overlap, i.e. there are watchdog triggers that also detect a heap corruption, and some heap corruptions probably are just not detected yet due to the light impact detection mode.
So please keep looking for potential heap corruption sources.
Btw, the config mutex didn't show a significant crash reduction in the records, but it should still help reduce the /store corruptions (time will tell).
Regards,
Michael
Am 29.12.25 um 12:11 schrieb Michael Balzer via OvmsDev:
Checking the heap immediately on events will probably not catch bugs that involve late callbacks using already freed buffers, and some events also are signaled before the actual shutdown (release of all resources) has fully taken place.
To register the heap checker for a delayed execution, use this scheme:
# create custom heap checking event handler:
vfs echo "module check alert" /store/events/usr.check.heap/00-checkheap
# register delayed heap checks:
vfs echo "event raise -d5000 usr.check.heap" /store/events/server.v2.stopped/90-checkheap
vfs echo "event raise -d5000 usr.check.heap" /store/events/server.v3.stopped/90-checkheap
…
Note: just guessing with the 5 second delay here, may need more, depending on the event.
Maybe we should register the check to be done by default on some selected events. Although the heap check normally is done within milliseconds, I still hesitate doing that. The heap check needs to lock the system while walking through all allocated memory blocks, which may create issues for vehicles that rely on consistent timing for CAN or custom hardware communication.
Regards,
Michael
Am 29.12.25 um 11:42 schrieb Michael Balzer via OvmsDev:
The heap check + one-off alert function is now exposed for inclusion in component code and can be called as a shell command to enable inclusion in event scripts et al:
#include "ovms_module.h"
/**
* module_check_heap_alert: check for and send one-off alert notification on heap corruption
*
* To enable the check every 5 minutes, set config "module" "debug.heap" to "yes".
*
* To add custom checks, call from your code, or register event scripts as needed.
* Example: perform heap integrity check when the server V2 gets stopped:
* vfs echo "module check alert" /store/events/server.v2.stopped/90-checkheap
*
* @param verbosity -- optional: channel capacity (default 0)
* @param OvmsWriter -- optional: channel (default NULL)
* @return heapok -- false = heap corrupted/full
*/
extern bool module_check_heap_alert(int verbosity=0, OvmsWriter* writer=NULL);
Regards,
Michael
Am 28.12.25 um 19:21 schrieb Michael Balzer via OvmsDev:
PS: when creating a debug build, you may also consider enabling the "comprehensive" corruption detection mode, as that will catch more cases.
But be aware that has a substantial impact on performance, so a user will probably not tolerate this for regular daily use.
Regards,
Michael
Am 28.12.25 um 18:26 schrieb Michael Balzer via OvmsDev:
Everyone,
from the crash reports (https://ovms.dexters-web.de/firmware/developer/), most remaining crashes seem to be caused by heap corruptions.
Not all heap corruptions are easily detectable from the backtrace analysis, and the component or action causing the corruption isn't detectable at all that way. So I've added a debug option to enable a regular heap integrity check ever 5 minutes, with the module sending an alert notification when a corruption has been detected. Example:
Heap corruption detected; reboot advised ASAP!
Please forward including task records and system log:
CORRUPT HEAP: Bad tail at 0x3f8e44f0 owner 0x3ffea9bc. Expected 0xbaad5678 got 0xbaad5600
I also added a final heap integrity check to our crash handler, so the crash debug records should now show exactly which crashes occurred with a corrupted heap.
In combination with the system log and the task log, that should give us some more opportunities to narrow down the cause(s).
I've also added task ownershop to the heap corruption report. Note, this needs my latest additions to our esp-idf fork, so take care to pull these before building.
Be aware, task ownership of corrupted blocks doesn't necessarily tell about the task doing the corruption. If the tail canary is compromised, and no other block located before that block is compromised, it *may* be that task doing the out of bounds write. But it may also be a use after free of some previous owner. So take task ownership with a grain of salt.
The corruptions are most probably caused by some unclean shutdown of a component or by an undetected race conditions within a shutdown procedure. The heap seems to be stable on modules with standard configurations and components not being started & shut down on a regular base. The heap corruptions are especially present now with Smart (SQ) vehicles -- as the Smart doesn't keep the 12V battery charged from the main battery, most Smart users probably use the power management to shut down Wifi and/or modem while parking.
So our main focus should be on analysing what happens before the corruption. Ask users reporting heap corruptions to provide their system logs, and possibly also their task logs. To encourage enabling these, I've added the config to the web UI (Config→Notifications).
Once you can reproduce (!) the corruption, heap tracing might provide some more insight as to where exactly the corruption occurs.
Heap tracing means recording all memory allocations and frees. This adds a recording layer on top of the heap functions, so comes with some cost, even when inactive. CPU overhead is low, but stack overhead may be an issue, so I think we should not enable heap tracing by default for now, but rather use a debug build specifically in cases we think heap tracing might help.
To enable heap tracing on some user device, I've reworked the ESP-IDF heap tracing to enable remote execution and to also include the task handles performing the allocations and deallocations.
To enable heap tracing for a build:
- Under
make menuconfig, navigate toComponent settings->Heap Memory Debuggingand set CONFIG_HEAP_TRACING.
There's also an option to set the number of stack backtrace frames. Tracing with two frames is mostly useless in our (C++) context, as it will normally only show some inner frames of the allocator. I've tried raising that to 5, and got an immediate crash in the mdns component. I assume raising the depth will need raising some stack sizes. If you find a good compromise, please report.
Heap tracing will work best in a reduced configuration. In normal operation, my module fills a 500 records buffer within seconds. The buffer is a FIFO, so will always contain the latest n allocations, and the last entry in the dump is the newest one.
Reduced example dump:
OVMS# mod trace dump
Heap tracing started/resumed at ccount 0x1c70b453 = logtime 19415
1000 allocations trace (1000 entry buffer)
258 bytes (@ 0x3fffb3a8) allocated CPU 1 task 0x3ffc92e8 ccount 0x89074e74 caller 0x4031d4f0:0x4031f553
freed task 0x3ffc92e8 by 0x4031d514:0x4031f595
201 bytes (@ 0x3f8e92f4) allocated CPU 1 task 0x3fff2290 ccount 0x89218bbc caller 0x40131b12:0x4014633c
freed task 0x3fff2290 by 0x402c4634:0x402cb14d
112 bytes (@ 0x3ffebc80) allocated CPU 1 task 0x3ffee918 ccount 0x8a25d47c caller 0x4029b455:0x4017a5dc
freed task 0x3ffee918 by 0x4029b744:0x4017a5dc
112 bytes (@ 0x3ffebc80) allocated CPU 1 task 0x3ffee918 ccount 0x8db89c40 caller 0x4029b455:0x4017a5dc
freed task 0x3ffee918 by 0x4029b744:0x4017a5dc
12 bytes (@ 0x3f85d0d4) allocated CPU 1 task 0x3ffdfcd0 ccount 0x8fccdfd8 caller 0x40131b12:0x4014633c
freed task 0x3ffdfcd0 by 0x402c4634:0x401e0a04
[…]
12 bytes (@ 0x3f85d0d4) allocated CPU 1 task 0x3ffdfcd0 ccount 0x3cf429f4 caller 0x40131b12:0x4014633c
freed task 0x3ffdfcd0 by 0x402c4634:0x401e0a04
112 bytes (@ 0x3ffebc80) allocated CPU 1 task 0x3ffee918 ccount 0x3fe1a0bc caller 0x4029b455:0x4017a5dc
229 bytes alive in trace (3/1000 allocations)
total allocations 1207 total frees 3356
(NB: Buffer has overflowed; so trace data is incomplete.)
"ccount" is the ESP32 CCOUNT register (CPU cycles), so provides an orientation on when the allocation occurred.
Some more basics on heap debugging are also covered here: https://docs.espressif.com/projects/esp-idf/en/v3.3/api-reference/system/heap_debug.html
Regards,
Michael
-- Michael Balzer * Am Rahmen 5 * D-58313 Herdecke Fon 02330 9104094 * Handy 0176 20698926
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