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Petr Machata says: ==================== net: sched: Do not drop root lock in tcf_qevent_handle() Mirred currently does not mix well with blocks executed after the qdisc root lock is taken. This includes classification blocks (such as in PRIO, ETS, DRR qdiscs) and qevents. The locking caused by the packet mirrored by mirred can cause deadlocks: either when the thread of execution attempts to take the lock a second time, or when two threads end up waiting on each other's locks. The qevent patchset attempted to not introduce further badness of this sort, and dropped the lock before executing the qevent block. However this lead to too little locking and races between qdisc configuration and packet enqueue in the RED qdisc. Before the deadlock issues are solved in a way that can be applied across many qdiscs reasonably easily, do for qevents what is done for the classification blocks and just keep holding the root lock. That is done in patch #1. Patch #2 then drops the now unnecessary root_lock argument from Qdisc_ops.enqueue. ==================== Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Linux kernel
============
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