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netpoll: allow cleanup to be synchronous

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This fixes a problem introduced by:
commit 2cde6acd49 ("netpoll: Fix __netpoll_rcu_free so that it can hold the rtnl lock")

When using netconsole on a bond, __netpoll_cleanup can asynchronously
recurse multiple times, each __netpoll_free_async call can result in
more __netpoll_free_async's. This means there is now a race between
cleanup_work queues on multiple netpoll_info's on multiple devices and
the configuration of a new netpoll. For example if a netconsole is set
to enable 0, reconfigured, and enable 1 immediately, this netconsole
will likely not work.

Given the reason for __netpoll_free_async is it can be called when rtnl
is not locked, if it is locked, we should be able to execute
synchronously. It appears to be locked everywhere it's called from.

Generalize the design pattern from the teaming driver for current
callers of __netpoll_free_async.

CC: Neil Horman <nhorman@tuxdriver.com>
CC: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Debabrata Banerjee <dbanerje@akamai.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Debabrata Banerjee
2018-10-18 11:18:26 -04:00
committed by David S. Miller
parent 2e2d6f0342
commit c9fbd71f73
8 changed files with 13 additions and 29 deletions
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2
net/dsa/slave.c
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@@ -722,7 +722,7 @@ static void dsa_slave_netpoll_cleanup(struct net_device *dev)
p->netpoll = NULL;
__netpoll_free_async(netpoll);
__netpoll_free(netpoll);
}
static void dsa_slave_poll_controller(struct net_device *dev)