| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <BANLkTimh79=gvOEsrHEmBox2LVUwM=LvLA@mail.gmail.com>
Date: Thu, 21 Apr 2011 15:08:28 +0800
From: Yong Zhang <yong.zhang0@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
Andrew Morton <akpm@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
Peter Zijlstra <peterz@...radead.org>,
"H. Peter Anvin" <hpa@...or.com>,
Frederic Weisbecker <fweisbec@...il.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 1/7] lockdep: Print a nice description of an irq locking issue
On Thu, Apr 21, 2011 at 3:02 PM, Yong Zhang <yong.zhang0@...il.com> wrote:
> On Thu, Apr 21, 2011 at 9:41 AM, Steven Rostedt <rostedt@...dmis.org> wrote:
>> ---
>>
>> The above is the case when the unsafe lock is taken while holding
>> a lock taken in irq context. But when a lock is taken that also
>> grabs a unsafe lock, the call chain is shown:
>>
>> ---
>> other info that might help us debug this:
>>
>> Chain exists of:
>> &rq->lock --> lockA --> lockC
>>
>> Possible interrupt unsafe locking scenario:
>>
>> CPU0 CPU1
>> ---- ----
>> lock(lockC);
>> local_irq_disable();
>> lock(&rq->lock);
>> lock(lockA);
>> <Interrupt>
>> lock(&rq->lock);
>>
>> *** DEADLOCK ***
>
> Or we could show this:
> Chain exists of:
> &rq->lock --> lockA --> lockC
>
> Possible interrupt unsafe locking scenario:
>
> CPU0 CPU1 CPU2
> ---- ---- ----
> lock(lockC);
> local_irq_disable();
Forget
local_irq_disable(); here :)
> lock(&rq->lock); lock(lockA);
> lock(lockA); lock(lockC);
> <Interrupt>
> lock(&rq->lock);
>
> *** DEADLOCK ***
>
> Thanks,
> Yong
>
>>
>> Acked-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
>> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
>> ---
>> kernel/lockdep.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>> 1 files changed, 70 insertions(+), 0 deletions(-)
>>
>> diff --git a/kernel/lockdep.c b/kernel/lockdep.c
>> index 0d2058d..bb77c030 100644
>> --- a/kernel/lockdep.c
>> +++ b/kernel/lockdep.c
>> @@ -490,6 +490,18 @@ void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
>> usage[i] = '\0';
>> }
>>
>> +static int __print_lock_name(struct lock_class *class)
>> +{
>> + char str[KSYM_NAME_LEN];
>> + const char *name;
>> +
>> + name = class->name;
>> + if (!name)
>> + name = __get_key_name(class->key, str);
>> +
>> + return printk("%s", name);
>> +}
>> +
>> static void print_lock_name(struct lock_class *class)
>> {
>> char str[KSYM_NAME_LEN], usage[LOCK_USAGE_CHARS];
>> @@ -1325,6 +1337,62 @@ print_shortest_lock_dependencies(struct lock_list *leaf,
>> return;
>> }
>>
>> +static void
>> +print_irq_lock_scenario(struct lock_list *safe_entry,
>> + struct lock_list *unsafe_entry,
>> + struct held_lock *prev,
>> + struct held_lock *next)
>> +{
>> + struct lock_class *safe_class = safe_entry->class;
>> + struct lock_class *unsafe_class = unsafe_entry->class;
>> + struct lock_class *middle_class = hlock_class(prev);
>> +
>> + if (middle_class == safe_class)
>> + middle_class = hlock_class(next);
>> +
>> + /*
>> + * A direct locking problem where unsafe_class lock is taken
>> + * directly by safe_class lock, then all we need to show
>> + * is the deadlock scenario, as it is obvious that the
>> + * unsafe lock is taken under the safe lock.
>> + *
>> + * But if there is a chain instead, where the safe lock takes
>> + * an intermediate lock (middle_class) where this lock is
>> + * not the same as the safe lock, then the lock chain is
>> + * used to describe the problem. Otherwise we would need
>> + * to show a different CPU case for each link in the chain
>> + * from the safe_class lock to the unsafe_class lock.
>> + */
>> + if (middle_class != unsafe_class) {
>> + printk("Chain exists of:\n ");
>> + __print_lock_name(safe_class);
>> + printk(" --> ");
>> + __print_lock_name(middle_class);
>> + printk(" --> ");
>> + __print_lock_name(unsafe_class);
>> + printk("\n\n");
>> + }
>> +
>> + printk(" Possible interrupt unsafe locking scenario:\n\n");
>> + printk(" CPU0 CPU1\n");
>> + printk(" ---- ----\n");
>> + printk(" lock(");
>> + __print_lock_name(unsafe_class);
>> + printk(");\n");
>> + printk(" local_irq_disable();\n");
>> + printk(" lock(");
>> + __print_lock_name(safe_class);
>> + printk(");\n");
>> + printk(" lock(");
>> + __print_lock_name(middle_class);
>> + printk(");\n");
>> + printk(" <Interrupt>\n");
>> + printk(" lock(");
>> + __print_lock_name(safe_class);
>> + printk(");\n");
>> + printk("\n *** DEADLOCK ***\n\n");
>> +}
>> +
>> static int
>> print_bad_irq_dependency(struct task_struct *curr,
>> struct lock_list *prev_root,
>> @@ -1376,6 +1444,8 @@ print_bad_irq_dependency(struct task_struct *curr,
>> print_stack_trace(forwards_entry->class->usage_traces + bit2, 1);
>>
>> printk("\nother info that might help us debug this:\n\n");
>> + print_irq_lock_scenario(backwards_entry, forwards_entry, prev, next);
>> +
>> lockdep_print_held_locks(curr);
>>
>> printk("\nthe dependencies between %s-irq-safe lock", irqclass);
>> --
>> 1.7.2.3
>>
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>> the body of a message to majordomo@...r.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>> Please read the FAQ at http://www.tux.org/lkml/
>>
>
>
>
> --
> Only stand for myself
>
--
Only stand for myself
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists