linux-kernel - Re: [PATCH v2 2/2] uprobes: Remove the spinlock within handle

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Message-ID: <1f40c2c1-1cf3-0fea-5e2b-38bde0f2fb2c@huawei.com>
Date: Tue, 13 Aug 2024 20:30:21 +0800
From: "Liao, Chang" <liaochang1@...wei.com>
To: Oleg Nesterov <oleg@...hat.com>
CC: <mhiramat@...nel.org>, <peterz@...radead.org>, <mingo@...hat.com>,
	<acme@...nel.org>, <namhyung@...nel.org>, <mark.rutland@....com>,
	<alexander.shishkin@...ux.intel.com>, <jolsa@...nel.org>,
	<irogers@...gle.com>, <adrian.hunter@...el.com>, <kan.liang@...ux.intel.com>,
	<andrii@...nel.org>, <rostedt@...dmis.org>, <linux-kernel@...r.kernel.org>,
	<linux-trace-kernel@...r.kernel.org>, <linux-perf-users@...r.kernel.org>,
	<bpf@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] uprobes: Remove the spinlock within
 handle_singlestep()



在 2024/8/12 19:29, Oleg Nesterov 写道:
> On 08/09, Liao Chang wrote:
>>
>> --- a/include/linux/uprobes.h
>> +++ b/include/linux/uprobes.h
>> @@ -75,6 +75,7 @@ struct uprobe_task {
>>  
>>  	struct uprobe			*active_uprobe;
>>  	unsigned long			xol_vaddr;
>> +	bool				deny_signal;
> 
> Ack, but... I can't believe I am arguing with the naming ;)
> Can we have a better name for this flag?
> 
> 	utask->signal_denied ?
> 	utask->restore_sigpending ?

I prefer the name "signal_denied" as it more accurately reflects
what happened.

> 
> or just
> 
> 	utask->sigpending ?
> 
> utask->deny_signal looks as if handle_singlestep/whatever should
> "deny" the pending signal cleared by uprobe_deny_signal(), while
> it fact it should restore TIF_SIGPENDING.

Make sense. I will change the name in v3.

> 
> Oleg.
> 
>>  
>>  	struct return_instance		*return_instances;
>>  	unsigned int			depth;
>> diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
>> index 76a51a1f51e2..77934fbd1370 100644
>> --- a/kernel/events/uprobes.c
>> +++ b/kernel/events/uprobes.c
>> @@ -1979,6 +1979,7 @@ bool uprobe_deny_signal(void)
>>  	WARN_ON_ONCE(utask->state != UTASK_SSTEP);
>>  
>>  	if (task_sigpending(t)) {
>> +		utask->deny_signal = true;
>>  		clear_tsk_thread_flag(t, TIF_SIGPENDING);
>>  
>>  		if (__fatal_signal_pending(t) || arch_uprobe_xol_was_trapped(t)) {
>> @@ -2288,9 +2289,10 @@ static void handle_singlestep(struct uprobe_task *utask, struct pt_regs *regs)
>>  	utask->state = UTASK_RUNNING;
>>  	xol_free_insn_slot(current);
>>  
>> -	spin_lock_irq(&current->sighand->siglock);
>> -	recalc_sigpending(); /* see uprobe_deny_signal() */
>> -	spin_unlock_irq(&current->sighand->siglock);
>> +	if (utask->deny_signal) {
>> +		set_thread_flag(TIF_SIGPENDING);
>> +		utask->deny_signal = false;
>> +	}
>>  
>>  	if (unlikely(err)) {
>>  		uprobe_warn(current, "execute the probed insn, sending SIGILL.");
>> -- 
>> 2.34.1
>>
> 
> 

-- 
BR
Liao, Chang