On Sat, 8 Oct 2005, Aritz Bastida wrote:
As I have read in net/core/dev.c there are two "locks" related to
devices: rtnl semaphore and dev_base_lock reader/writer spinlock.
This comment relates to dev_base only.
The rtnl semaphore serializes any updates in the networking, making sure
there is only one caller updating network parameters at a time.
the dev_base lock makes sure nobody is pulling your feets while reading
the dev_base linked list of devices (i.e. guarantees that the device won't
disappear under your feets).
The actual flags as such is indeed not protected by a lock and there is a
slight chance of inconsistent results (part new, part old) if the flags is
being read while updated by another call.
In dev_ifsioc() there is no new locking. It gets or changes the flags,
depending the case. Now, why there is no call to write_lock()? The
comments in net/core/dev.c suggest that you should take the spinlock
for writing, but they dont do that.
There is no write lock because the dev_base list is not modified.
Regards
Henrik
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