Re: [PATCH 6/9] hashmap: Add re-entrancy support to foreach function
Hi Jukka,
On 02/10/2015 08:42 AM, Jukka Rissanen wrote:
Allow user to remove and add values while inside a callback
from foreach function. This is very much needed as it is
easy to get things wrong here and it helps to avoid complicated
call flows in calling applications.
Can you tell me why this is needed? This sounds like abuse of
hashmap_foreach and an alternate data structure might be in order.
So foreach logic is changed so that if user tries to remove
an entry from the hash while inside foreach callback, the
entry is not yet removed from hash but marked as removable.
After foreach has finished calling the callback function,
it checks what elements it needs to remove from the hash.
So let me politely say: "No way are we doing this" ;)
This valgrind report was seen and it relates to this issue.
Here a DBus message was received and its callback function
eventually called l_dbus_unregister() because of application
logic. This then caused the signal_list hash to get corrupted
because the unregister removed an entry from hash while
traversing it.
So I think I understand why you're doing this...
l_dbus_register and l_dbus_unregister need to actually go away. They
are not workable long term. We need a way smarter data structure to
handle signal filtering.
Look at libsystemd/sd-bus/bus-match.c for some inspiration.
Regards,
-Denis