Messages in this thread | | | Subject | Re:Sleeping in RCU list traversal | From | Jun WANG <> | Date | Mon, 08 Oct 2007 03:11:47 +0800 |
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Hi >Something like this? > >rcu_read_lock(); >list_for_each_rcu(p, ...) { > ptr = list_entry(p, struct ..., list); > /* Grab a reference to "ptr". */ > rcu_read_unlock(); > my_task_that_may_sleep(ptr); > rcu_read_lock(); > /* Drop a reference to "ptr". */ >} >rcu_read_unlock();
>Regarding my case, memory region pointed by "ptr" never be removed. >Do I need to grab a reference to "ptr" ? In Document/RCU/whatisRCU.txt Note that the value returned by rcu_dereference() is valid only within the enclosing RCU read-side critical section. For example, the following is -not- legal:
rcu_read_lock(); p = rcu_dereference(head.next); rcu_read_unlock(); x = p->address; rcu_read_lock(); y = p->data; rcu_read_unlock();
Holding a reference from one RCU read-side critical section to another is just as illegal as holding a reference from one lock-based critical section to another! Similarly, using a reference outside of the critical section in which it was acquired is just as illegal as doing so with normal locking. Jun Wang
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