Re: [PATCH 1/4] riscv: avoid kernel hangs when trapped in BUG()

[Paul Walmsley]

On Mon, 23 Sep 2019, Vincent Chen wrote:

> When the CONFIG_GENERIC_BUG is disabled by disabling CONFIG_BUG, if a
> kernel thread is trapped by BUG(), the whole system will be in the
> loop that infinitely handles the ebreak exception instead of entering the
> die function. To fix this problem, the do_trap_break() will always call
> the die() to deal with the break exception as the type of break is
> BUG_TRAP_TYPE_BUG.
> 
> Signed-off-by: Vincent Chen 

Thanks, queued for v5.4-rc.


- Paul

Re: [PATCH 1/4] riscv: avoid kernel hangs when trapped in BUG()

[Christoph Hellwig]

On Mon, Sep 23, 2019 at 08:45:14AM +0800, Vincent Chen wrote:
> When the CONFIG_GENERIC_BUG is disabled by disabling CONFIG_BUG, if a
> kernel thread is trapped by BUG(), the whole system will be in the
> loop that infinitely handles the ebreak exception instead of entering the
> die function. To fix this problem, the do_trap_break() will always call
> the die() to deal with the break exception as the type of break is
> BUG_TRAP_TYPE_BUG.
> 
> Signed-off-by: Vincent Chen 

Looks good,

Reviewed-by: Christoph Hellwig 

[PATCH 1/4] riscv: avoid kernel hangs when trapped in BUG()

[Vincent Chen]

When the CONFIG_GENERIC_BUG is disabled by disabling CONFIG_BUG, if a
kernel thread is trapped by BUG(), the whole system will be in the
loop that infinitely handles the ebreak exception instead of entering the
die function. To fix this problem, the do_trap_break() will always call
the die() to deal with the break exception as the type of break is
BUG_TRAP_TYPE_BUG.

Signed-off-by: Vincent Chen 
---
 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 424eb72d56b1..055a937aca70 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -124,23 +124,23 @@ static inline unsigned long 
get_break_insn_length(unsigned long pc)
 
 asmlinkage void do_trap_break(struct pt_regs *regs)
 {
-#ifdef CONFIG_GENERIC_BUG
if (!user_mode(regs)) {
enum bug_trap_type type;
 
type = report_bug(regs->sepc, regs);
switch (type) {
+#ifdef CONFIG_GENERIC_BUG
case BUG_TRAP_TYPE_NONE:
break;
case BUG_TRAP_TYPE_WARN:
regs->sepc += get_break_insn_length(regs->sepc);
break;
case BUG_TRAP_TYPE_BUG:
+#endif /* CONFIG_GENERIC_BUG */
+   default:
die(regs, "Kernel BUG");
}
}
-#endif /* CONFIG_GENERIC_BUG */
-
force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)(regs->sepc));
 }
 
-- 
2.7.4