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tipc: make macro tipc_wait_for_cond() smp safe

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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 365ad353c2 ("tipc: reduce risk of user starvation during link congestion")
Reviewed-by: Parthasarathy Bhuvaragan <parthasarathy.bhuvaragan@ericsson.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jon Paul Maloy 2017-05-11 20:28:15 +02:00 committed by David S. Miller
parent ad990dbe6d
commit 844cf763fb
1 changed files with 19 additions and 19 deletions
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38
net/tipc/socket.c
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@ -362,25 +362,25 @@ static int tipc_sk_sock_err(struct socket *sock, long *timeout)
return 0;
}
#define tipc_wait_for_cond(sock_, timeout_, condition_) \
({ \
int rc_ = 0; \
int done_ = 0; \
\
while (!(condition_) && !done_) { \
struct sock *sk_ = sock->sk; \
DEFINE_WAIT_FUNC(wait_, woken_wake_function); \
\
rc_ = tipc_sk_sock_err(sock_, timeout_); \
if (rc_) \
break; \
prepare_to_wait(sk_sleep(sk_), &wait_, \
TASK_INTERRUPTIBLE); \
done_ = sk_wait_event(sk_, timeout_, \
(condition_), &wait_); \
remove_wait_queue(sk_sleep(sk_), &wait_); \
} \
rc_; \
#define tipc_wait_for_cond(sock_, timeo_, condition_) \
({ \
struct sock *sk_; \
int rc_; \
\
while ((rc_ = !(condition_))) { \
DEFINE_WAIT_FUNC(wait_, woken_wake_function); \
sk_ = (sock_)->sk; \
rc_ = tipc_sk_sock_err((sock_), timeo_); \
if (rc_) \
break; \
prepare_to_wait(sk_sleep(sk_), &wait_, TASK_INTERRUPTIBLE); \
release_sock(sk_); \
*(timeo_) = wait_woken(&wait_, TASK_INTERRUPTIBLE, *(timeo_)); \
sched_annotate_sleep(); \
lock_sock(sk_); \
remove_wait_queue(sk_sleep(sk_), &wait_); \
} \
rc_; \
})
/**