netdev - Re: [PATCH net 1/1] tipc: make macro tipc_wait_for

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Message-Id: <20170511.222006.1297917220396086411.davem@davemloft.net>
Date:   Thu, 11 May 2017 22:20:06 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     jon.maloy@...csson.com
Cc:     netdev@...r.kernel.org, parthasarathy.bhuvaragan@...csson.com,
        ying.xue@...driver.com, tipc-discussion@...ts.sourceforge.net
Subject: Re: [PATCH net 1/1] tipc: make macro tipc_wait_for_cond() smp safe

From: Jon Maloy <jon.maloy@...csson.com>
Date: Thu, 11 May 2017 20:28:15 +0200

> The macro tipc_wait_for_cond() is embedding the macro sk_wait_event()
> to fulfil its task. The latter, in turn, is evaluating the stated
> condition outside the socket lock context. This is problematic if
> the condition is accessing non-trivial data structures which may be
> altered by incoming interrupts, as is the case with the cong_links()
> linked list, used by socket to keep track of the current set of
> congested links. We sometimes see crashes when this list is accessed
> by a condition function at the same time as a SOCK_WAKEUP interrupt
> is removing an element from the list.
> 
> We fix this by expanding selected parts of sk_wait_event() into the
> outer macro, while ensuring that all evaluations of a given condition
> are performed under socket lock protection.
> 
> Fixes: commit 365ad353c256 ("tipc: reduce risk of user starvation
> during link congestion")
> 
> Reviewed-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@...csson.com>
> Signed-off-by: Jon Maloy <jon.maloy@...csson.com>

Applied and queued up for -stable, thanks Jon.