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authorDavid Howells <dhowells@redhat.com>2016-09-24 23:00:54 +0100
committerDavid Howells <dhowells@redhat.com>2016-09-24 23:49:46 +0100
commitdf0562a72dba13ab49c7dd7cb15170697b9848ee (patch)
treef486a25fd8590a0ea2b873ea4f0e31dee637ed7e /net/rxrpc
parentdd7c1ee59a90ca8a75bce72c721851d5550f3c59 (diff)
downloadlinux-df0562a72dba13ab49c7dd7cb15170697b9848ee.tar.bz2
rxrpc: Delay the resend timer to allow for nsec->jiffies conv error
When determining the resend timer value, we have a value in nsec but the timer is in jiffies which may be a million or more times more coarse. nsecs_to_jiffies() rounds down - which means that the resend timeout expressed as jiffies is very likely earlier than the one expressed as nanoseconds from which it was derived. The problem is that rxrpc_resend() gets triggered by the timer, but can't then find anything to resend yet. It sets the timer again - but gets kicked off immediately again and again until the nanosecond-based expiry time is reached and we actually retransmit. Fix this by adding 1 to the jiffies-based resend_at value to counteract the rounding and make sure that the timer happens after the nanosecond-based expiry is passed. Alternatives would be to adjust the timestamp on the packets to align with the jiffie scale or to switch back to using jiffie-timestamps. Signed-off-by: David Howells <dhowells@redhat.com>
Diffstat (limited to 'net/rxrpc')
-rw-r--r--net/rxrpc/call_event.c10
1 files changed, 8 insertions, 2 deletions
diff --git a/net/rxrpc/call_event.c b/net/rxrpc/call_event.c
index a78a92fe5d77..d5bf9ce7ec6f 100644
--- a/net/rxrpc/call_event.c
+++ b/net/rxrpc/call_event.c
@@ -200,8 +200,14 @@ static void rxrpc_resend(struct rxrpc_call *call)
ktime_to_ns(ktime_sub(skb->tstamp, max_age)));
}
- resend_at = ktime_sub(ktime_add_ms(oldest, rxrpc_resend_timeout), now);
- call->resend_at = jiffies + nsecs_to_jiffies(ktime_to_ns(resend_at));
+ resend_at = ktime_add_ms(oldest, rxrpc_resend_timeout);
+ call->resend_at = jiffies +
+ nsecs_to_jiffies(ktime_to_ns(ktime_sub(resend_at, now))) +
+ 1; /* We have to make sure that the calculated jiffies value
+ * falls at or after the nsec value, or we shall loop
+ * ceaselessly because the timer times out, but we haven't
+ * reached the nsec timeout yet.
+ */
/* Now go through the Tx window and perform the retransmissions. We
* have to drop the lock for each send. If an ACK comes in whilst the