daniel-p-carvalho opened a new issue, #20452:
URL: https://github.com/apache/nuttx/issues/20452
### Description / Steps to reproduce the issue
Since 19b4911d7f ("arch: remove up_current_regs in common code"), the MIPS
interrupt handlers save the interrupted context into
`g_running_tasks[this_cpu()]->xcp.regs` on entry, but nothing in the MIPS
interrupt path updates `g_running_tasks[]` after a context switch. The only
writers are `nx_start()` (Idle task) and `up_exit()` (sets it to NULL).
Consequences:
* Every interrupt copies the interrupted context into the TCB that
`g_running_tasks[]` points to (the Idle task), not the TCB of the task
that was really interrupted.
* After any task or thread exits, `g_running_tasks[]` stays NULL, no context
is saved on interrupt entry any more, and the next context switch restores
stale registers. The crash dump path also uses `g_running_tasks[]`, so the
resulting exception usually faults again inside `PANIC()`.
On PIC32MZ this was confirmed on hardware (PIC32MZ-W1 board): the system
crashed right after the network initialization thread exited. It is fixed
for PIC32MZ in #20450 by setting `g_running_tasks[this_cpu()] = this_task()`
before `pic32mz_decodeirq()` returns, as the ARM and RISC-V handlers do.
The same pattern is present in these handlers, which I cannot test (no
hardware):
* `arch/mips/src/pic32mx/pic32mx_decodeirq.c`
* `arch/mips/src/mips32/mips_doirq.c`
* `arch/mips/src/jz4780/jz4780_decodeirq.c`
Steps to reproduce on an affected board: enable a feature whose thread exits
after boot (e.g. `CONFIG_NETINIT_THREAD=y`), or run any NSH builtin as a
separate task, and wait for the next context switch after it exits.
### On which OS does this issue occur?
[OS: Linux]
### What is the version of your OS?
Ubuntu Linux x86_64
### NuttX Version
master
### Issue Architecture
[Arch: mips]
### Issue Area
[Area: Kernel]
### Verification
- [x] I have verified before submitting the report.
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