Messages in this thread | | | From | Emil Langrock <> | Subject | Recursive deactivation of local bottom halves | Date | Tue, 25 Jan 2011 14:05:14 +0100 |
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Hi,
I wanted or more or less had to do following:
... spin_lock_bh(lock1); .... spin_lock_bh(lock2); ... spin_unlock_bh(lock2); .... spin_unlock_bh(lock1); ....
Now some weird behavior were noticed by a second person and he fixed it by removing the _bh from the inner spinlocks. I checked what the difference is and here is the previous example without the common spin_lock behaviour:
... local_bh_disable(); .... local_bh_disable(); ... local_bh_enable(); .... local_bh_enable(); ....
According to http://people.netfilter.org/rusty/unreliable-guides/kernel- hacking/routines-softirqs.html it makes no difference how often I use the pair local_bh_disable/local_bh_enable inside local_bh_disable/local_bh_enable. So was this changed?
I also couldn't find any indication in the kernel/softirq.c in the local_bh_enable functionality that the counting in local_bh_disable makes any difference.
Can somebody tell me if that is legal or not (on smp and uniprocessor)? And maybe can show me the related source code why is it may or may not be legal?
Kind regards, Emil
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