On 2024-11-18 10:13:33 [+0100], Nam Cao wrote:
> die() can be called in exception handler, and therefore cannot sleep.
> However, die() takes spinlock_t which can sleep with PREEMPT_RT enabled.
> That causes the following warning:
>
> BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
> in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 285, name: mutex
> preempt_count: 110001, expected: 0
> RCU nest depth: 0, expected: 0
> CPU: 0 UID: 0 PID: 285 Comm: mutex Not tainted 6.12.0-rc7-00022-ge19049cf7d56-dirty #234
> Hardware name: riscv-virtio,qemu (DT)
> Call Trace:
> dump_backtrace+0x1c/0x24
> show_stack+0x2c/0x38
> dump_stack_lvl+0x5a/0x72
> dump_stack+0x14/0x1c
> __might_resched+0x130/0x13a
> rt_spin_lock+0x2a/0x5c
> die+0x24/0x112
> do_trap_insn_illegal+0xa0/0xea
> _new_vmalloc_restore_context_a0+0xcc/0xd8
> Oops - illegal instruction [#1]
>
> Switch to use raw_spinlock_t, which does not sleep even with PREEMPT_RT
> enabled.
>
> Fixes: 76d2a0493a17 ("RISC-V: Init and Halt Code")
> Signed-off-by: Nam Cao <namcao@xxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
The die_lock() is probably do let one CPU die at a time. On x86 there is
support for for recursive die so if it happens, you don't spin on the
die_lock and see nothing. Not sure if this is a thing.
Sebastian
