linux-kernel - Re: [PATCH] rcu: Handle failure of memory allocation functions

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Date:   Sun, 12 Jun 2022 14:11:09 +0800
From:   liqiong <liqiong@...china.com>
To:     paulmck@...nel.org
Cc:     Davidlohr Bueso <dave@...olabs.net>,
        Josh Triplett <josh@...htriplett.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        linux-kernel@...r.kernel.org, rcu@...r.kernel.org,
        hukun@...china.com, qixu@...china.com, yuzhe@...china.com,
        renyu@...china.com
Subject: Re: [PATCH] rcu: Handle failure of memory allocation functions



在 2022年06月12日 00:34, Paul E. McKenney 写道:
> On Sat, Jun 11, 2022 at 05:30:55PM +0800, Li Qiong wrote:
>> Add warning when these functions (eg:kmalloc,vmalloc) fail, handle the
>> failure.
>>
>> Signed-off-by: Li Qiong <liqiong@...china.com>
> Good catch, thank you!  However...
>
>> ---
>>  kernel/rcu/rcutorture.c | 8 ++++++++
>>  1 file changed, 8 insertions(+)
>>
>> diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
>> index 7120165a9342..97f90e304ae3 100644
>> --- a/kernel/rcu/rcutorture.c
>> +++ b/kernel/rcu/rcutorture.c
>> @@ -1991,6 +1991,10 @@ static void rcu_torture_mem_dump_obj(void)
>>  
>>  	kcp = kmem_cache_create("rcuscale", 136, 8, SLAB_STORE_USER, NULL);
> As long as we are checking, why not also check this one?
>
> 							Thanx, Paul

Hi Paul,
Yes,  the kmem_cache_create  would fail too. 
I searched  "kernel" directory, found that It seems  all the code just check kmem_cache_alloc()，
So, I ignored   kmem_cache_create() .  I will submit a v2 patch.

Thanks,
Li Qiong


>
>>  	rhp = kmem_cache_alloc(kcp, GFP_KERNEL);
>> +	if (WARN_ON_ONCE(!rhp)) {
>> +		kmem_cache_destroy(kcp);
>> +		return;
>> +	}
>>  	pr_alert("mem_dump_obj() slab test: rcu_torture_stats = %px, &rhp = %px, rhp = %px, &z = %px\n", stats_task, &rhp, rhp, &z);
>>  	pr_alert("mem_dump_obj(ZERO_SIZE_PTR):");
>>  	mem_dump_obj(ZERO_SIZE_PTR);
>> @@ -2007,6 +2011,8 @@ static void rcu_torture_mem_dump_obj(void)
>>  	kmem_cache_free(kcp, rhp);
>>  	kmem_cache_destroy(kcp);
>>  	rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
>> +	if (WARN_ON_ONCE(!rhp))
>> +		return;
>>  	pr_alert("mem_dump_obj() kmalloc test: rcu_torture_stats = %px, &rhp = %px, rhp = %px\n", stats_task, &rhp, rhp);
>>  	pr_alert("mem_dump_obj(kmalloc %px):", rhp);
>>  	mem_dump_obj(rhp);
>> @@ -2014,6 +2020,8 @@ static void rcu_torture_mem_dump_obj(void)
>>  	mem_dump_obj(&rhp->func);
>>  	kfree(rhp);
>>  	rhp = vmalloc(4096);
>> +	if (WARN_ON_ONCE(!rhp))
>> +		return;
>>  	pr_alert("mem_dump_obj() vmalloc test: rcu_torture_stats = %px, &rhp = %px, rhp = %px\n", stats_task, &rhp, rhp);
>>  	pr_alert("mem_dump_obj(vmalloc %px):", rhp);
>>  	mem_dump_obj(rhp);
>> -- 
>> 2.11.0
>>