* Re: [RFC] re-document rculfstack and even rename it
[not found] <50752928.3050006@cn.fujitsu.com>
@ 2012-10-10 14:59 ` Paul E. McKenney
2012-10-11 18:22 ` Mathieu Desnoyers
[not found] ` <20121011182255.GA19783@Krystal>
2 siblings, 0 replies; 4+ messages in thread
From: Paul E. McKenney @ 2012-10-10 14:59 UTC (permalink / raw)
To: Lai Jiangshan; +Cc: lttng-dev, Mathieu Desnoyers
On Wed, Oct 10, 2012 at 03:52:08PM +0800, Lai Jiangshan wrote:
> rculfstack is not really require RCU-only.
>
> 1) cds_lfs_push_rcu() don't need any lock, don't need RCU nor other locks.
>
> 2) cds_lfs_pop_rcu() don't only one of the following synchronization(not only RCU):
> A) use rcu_read_lock() to protect cds_lfs_pop_rcu() and use synchronize_rcu()
> or call_rcu() to free the popped node. (current comments said we need this
> synchronization, and thus we named this struct with rcu prefix. But actually,
> the followings are OK, and are more popular/friendly)
> B) use mutexs/locks to protect cds_lfs_pop_rcu(), we can free to free/modify the
> popped node any time, we don't need any synchronization when free them.
> C) only ONE thread can call cds_lfs_pop_rcu(). (multi-providers-single customer)
> D) others, like read-write locks.
>
> I consider B) and C) are more popular. In linux kernel,
> kernel/task_work.c uses a hybird ways of B) and C).
>
> I suggest to rename it, Or document B) and C) at least.
Good timing -- stacks and queues are next on my list for documentation. ;-)
Thanx, Paul
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [RFC] re-document rculfstack and even rename it
[not found] <50752928.3050006@cn.fujitsu.com>
2012-10-10 14:59 ` [RFC] re-document rculfstack and even rename it Paul E. McKenney
@ 2012-10-11 18:22 ` Mathieu Desnoyers
[not found] ` <20121011182255.GA19783@Krystal>
2 siblings, 0 replies; 4+ messages in thread
From: Mathieu Desnoyers @ 2012-10-11 18:22 UTC (permalink / raw)
To: Lai Jiangshan; +Cc: lttng-dev, Paul E. McKenney
* Lai Jiangshan (laijs@cn.fujitsu.com) wrote:
> rculfstack is not really require RCU-only.
>
> 1) cds_lfs_push_rcu() don't need any lock, don't need RCU nor other locks.
Good point ! I even documented this peculiarness in the
comment at the top of _cds_lfs_push_rcu().
> 2) cds_lfs_pop_rcu() don't only one of the following synchronization(not only RCU):
> A) use rcu_read_lock() to protect cds_lfs_pop_rcu() and use synchronize_rcu()
> or call_rcu() to free the popped node. (current comments said we need this
> synchronization, and thus we named this struct with rcu prefix. But actually,
> the followings are OK, and are more popular/friendly)
> B) use mutexs/locks to protect cds_lfs_pop_rcu(), we can free to free/modify the
> popped node any time, we don't need any synchronization when free them.
> C) only ONE thread can call cds_lfs_pop_rcu(). (multi-providers-single customer)
> D) others, like read-write locks.
>
> I consider B) and C) are more popular. In linux kernel,
> kernel/task_work.c uses a hybird ways of B) and C).
>
> I suggest to rename it, Or document B) and C) at least.
Yes, agreed! Do you suggest we introduce a "lfstack", and slowly
deprecate rculfstack ?
We could then document the various ways to protect "pop", and also
implement a "splice" operation while we are there.
Thoughts ?
Thanks,
Mathieu
>
> Thanks,
> Lai
>
> _______________________________________________
> lttng-dev mailing list
> lttng-dev@lists.lttng.org
> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [RFC] re-document rculfstack and even rename it
[not found] ` <20121011182255.GA19783@Krystal>
@ 2012-10-12 2:25 ` Lai Jiangshan
0 siblings, 0 replies; 4+ messages in thread
From: Lai Jiangshan @ 2012-10-12 2:25 UTC (permalink / raw)
To: Mathieu Desnoyers; +Cc: lttng-dev, Paul E. McKenney
On 10/12/2012 02:22 AM, Mathieu Desnoyers wrote:
> * Lai Jiangshan (laijs@cn.fujitsu.com) wrote:
>> rculfstack is not really require RCU-only.
>>
>> 1) cds_lfs_push_rcu() don't need any lock, don't need RCU nor other locks.
>
> Good point ! I even documented this peculiarness in the
> comment at the top of _cds_lfs_push_rcu().
>
>> 2) cds_lfs_pop_rcu() don't only one of the following synchronization(not only RCU):
>> A) use rcu_read_lock() to protect cds_lfs_pop_rcu() and use synchronize_rcu()
>> or call_rcu() to free the popped node. (current comments said we need this
>> synchronization, and thus we named this struct with rcu prefix. But actually,
>> the followings are OK, and are more popular/friendly)
>> B) use mutexs/locks to protect cds_lfs_pop_rcu(), we can free to free/modify the
>> popped node any time, we don't need any synchronization when free them.
>> C) only ONE thread can call cds_lfs_pop_rcu(). (multi-providers-single customer)
>> D) others, like read-write locks.
>>
>> I consider B) and C) are more popular. In linux kernel,
>> kernel/task_work.c uses a hybird ways of B) and C).
>>
>> I suggest to rename it, Or document B) and C) at least.
>
> Yes, agreed! Do you suggest we introduce a "lfstack", and slowly
> deprecate rculfstack ?
>
> We could then document the various ways to protect "pop", and also
> implement a "splice" operation while we are there.
>
Acked.
Thanks,
Lai
^ permalink raw reply [flat|nested] 4+ messages in thread
* [RFC] re-document rculfstack and even rename it
@ 2012-10-10 7:52 Lai Jiangshan
0 siblings, 0 replies; 4+ messages in thread
From: Lai Jiangshan @ 2012-10-10 7:52 UTC (permalink / raw)
To: Paul E. McKenney, Mathieu Desnoyers, lttng-dev
rculfstack is not really require RCU-only.
1) cds_lfs_push_rcu() don't need any lock, don't need RCU nor other locks.
2) cds_lfs_pop_rcu() don't only one of the following synchronization(not only RCU):
A) use rcu_read_lock() to protect cds_lfs_pop_rcu() and use synchronize_rcu()
or call_rcu() to free the popped node. (current comments said we need this
synchronization, and thus we named this struct with rcu prefix. But actually,
the followings are OK, and are more popular/friendly)
B) use mutexs/locks to protect cds_lfs_pop_rcu(), we can free to free/modify the
popped node any time, we don't need any synchronization when free them.
C) only ONE thread can call cds_lfs_pop_rcu(). (multi-providers-single customer)
D) others, like read-write locks.
I consider B) and C) are more popular. In linux kernel,
kernel/task_work.c uses a hybird ways of B) and C).
I suggest to rename it, Or document B) and C) at least.
Thanks,
Lai
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2012-10-12 2:23 UTC | newest]
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[not found] <50752928.3050006@cn.fujitsu.com>
2012-10-10 14:59 ` [RFC] re-document rculfstack and even rename it Paul E. McKenney
2012-10-11 18:22 ` Mathieu Desnoyers
[not found] ` <20121011182255.GA19783@Krystal>
2012-10-12 2:25 ` Lai Jiangshan
2012-10-10 7:52 Lai Jiangshan
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