Messages in this thread | | | Date | Thu, 07 Nov 2019 16:12:49 -0800 (PST) | Subject | Re: [PATCH V2 net] net: hns: Fix the stray netpoll locks causing deadlock in NAPI path | From | David Miller <> |
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From: Salil Mehta <salil.mehta@huawei.com> Date: Thu, 7 Nov 2019 17:09:53 +0000
> This patch fixes the problem of the spin locks, originally > meant for the netpoll path of hns driver, causing deadlock in > the normal NAPI poll path. The issue happened due to the presence > of the stray leftover spin lock code related to the netpoll, > whose support was earlier removed from the HNS[1], got activated > due to enabling of NET_POLL_CONTROLLER switch. > > Earlier background: > The netpoll handling code originally had this bug(as identified > by Marc Zyngier[2]) of wrong spin lock API being used which did > not disable the interrupts and hence could cause locking issues. > i.e. if the lock were first acquired in context to thread like > 'ip' util and this lock if ever got later acquired again in > context to the interrupt context like TX/RX (Interrupts could > always pre-empt the lock holding task and acquire the lock again) > and hence could cause deadlock. > > Proposed Solution: > 1. If the netpoll was enabled in the HNS driver, which is not > right now, we could have simply used spin_[un]lock_irqsave() > 2. But as netpoll is disabled, therefore, it is best to get rid > of the existing locks and stray code for now. This should > solve the problem reported by Marc. > > [1] https://git.kernel.org/torvalds/c/4bd2c03be7 > [2] https://patchwork.ozlabs.org/patch/1189139/ > > Fixes: 4bd2c03be707 ("net: hns: remove ndo_poll_controller") > Reported-by: Marc Zyngier <maz@kernel.org> > Acked-by: Marc Zyngier <maz@kernel.org> > Tested-by: Marc Zyngier <maz@kernel.org> > Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
Applied and queued up for -stable, thanks.
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