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@linutronix.de Cc: stable@vger.kernel.org --- stable backport is probably not needed for versions earlier than 6.12 because PREEMPT_RT is not enabled. But it doesn't hurt.. --- arch/riscv/kernel/traps.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c index 51ebfd23e007..8ff8e8b36524 100644 --- a/arch/riscv/kernel/traps.c +++ b/arch/riscv/kernel/traps.c @@ -35,7 +35,7 @@
int show_unhandled_signals = 1;
-static DEFINE_SPINLOCK(die_lock); +static DEFINE_RAW_SPINLOCK(die_lock);
static int copy_code(struct pt_regs *regs, u16 *val, const u16 *insns) { @@ -81,7 +81,7 @@ void die(struct pt_regs *regs, const char *str)
oops_enter();
- spin_lock_irqsave(&die_lock, flags); + raw_spin_lock_irqsave(&die_lock, flags); console_verbose(); bust_spinlocks(1);
@@ -100,7 +100,7 @@ void die(struct pt_regs *regs, const char *str)
bust_spinlocks(0); add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE); - spin_unlock_irqrestore(&die_lock, flags); + raw_spin_unlock_irqrestore(&die_lock, flags); oops_exit();
if (in_interrupt())
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@linutronix.de Cc: stable@vger.kernel.org
Reviewed-by: Sebastian Andrzej Siewior bigeasy@linutronix.de
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
On Wed, 20 Nov 2024 00:50:45 PST (-0800), bigeasy@linutronix.de wrote:
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@linutronix.de Cc: stable@vger.kernel.org
Reviewed-by: Sebastian Andrzej Siewior bigeasy@linutronix.de
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.
Looks like the RISC-V code is pretty much the same as the arm64 code, so it probably just came from there. I don't really know what the right answer is here...
Sebastian
Hello:
This patch was applied to riscv/linux.git (fixes) by Palmer Dabbelt palmer@rivosinc.com:
On Mon, 18 Nov 2024 10:13:33 +0100 you 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]
[...]
Here is the summary with links: - riscv: Fix sleeping in invalid context in die() https://git.kernel.org/riscv/c/6a97f4118ac0
You are awesome, thank you!
linux-stable-mirror@lists.linaro.org
-
Nam Cao -
Palmer Dabbelt -
patchwork-bot+linux-riscv＠kernel.org -
Sebastian Andrzej Siewior