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SubjectRe: [PATCH RESEND] arm64: fault: avoid send SIGBUS two times
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On 2017/12/7 0:15, Will Deacon wrote:
>> --- a/arch/arm64/mm/fault.c
>> +++ b/arch/arm64/mm/fault.c
>> @@ -570,7 +570,6 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs)
>> {
>> struct siginfo info;
>> const struct fault_info *inf;
>> - int ret = 0;
>>
>> inf = esr_to_fault_info(esr);
>> pr_err("Synchronous External Abort: %s (0x%08x) at 0x%016lx\n",
>> @@ -585,7 +584,7 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs)
>> if (interrupts_enabled(regs))
>> nmi_enter();
>>
>> - ret = ghes_notify_sea();
>> + ghes_notify_sea();
>>
>> if (interrupts_enabled(regs))
>> nmi_exit();
>> @@ -600,7 +599,7 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs)
>> info.si_addr = (void __user *)addr;
>> arm64_notify_die("", regs, &info, esr);
>>
>> - return ret;
>> + return 0;
> Hmm, so this code is a bit of mess.
>
> Wouldn't it be better to have the signal dispatching code in do_mem_abort
> check ESR.ESR_ELx_FnV, so then do_sea wouldn't have to, and we could just
> return an error instead?

Thanks the mail and comments!

Regardless ghes_notify_sea()'s return value, it always needs to deliver signal,
because ghes_notify_sea()'s return value does not reflect whether the memory error
handler(memory_failure()) handle the error successfully or failed. If let do_mem_abort()
delivers the signal, we should always let do_sea() return error, then the do_mem_abort() can
always deliver signal. Then we will see the strange log as shown below when happen Synchronous External Abort.

[ 676.700652] Synchronous External Abort: synchronous external abort (0x96000410) at 0x0000000033ff7008
[ 676.723301] Unhandled fault: synchronous external abort (0x96000410) at 0x0000000033ff7008

so I think it is better send the signal in the do_sea(), not send it in the do_mem_abort().
do_mem_abort() only send the signal when the exception does not defined in fault_info[]. Another benefit
is that do_sea() can send different signal according to the Synchronous External Abort type, such as SIGBUS or SIGKILL.
the do_mem_abort() can only send one kind signal.


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