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| author | David Howells <dhowells@redhat.com> | 2016-09-24 23:00:54 +0100 |
|---|---|---|
| committer | David Howells <dhowells@redhat.com> | 2016-09-24 23:49:46 +0100 |
| commit | df0562a72dba13ab49c7dd7cb15170697b9848ee (patch) | |
| tree | f486a25fd8590a0ea2b873ea4f0e31dee637ed7e /net/rxrpc | |
| parent | dd7c1ee59a90ca8a75bce72c721851d5550f3c59 (diff) | |
| download | talos-obmc-linux-df0562a72dba13ab49c7dd7cb15170697b9848ee.tar.gz talos-obmc-linux-df0562a72dba13ab49c7dd7cb15170697b9848ee.zip | |
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.c | 10 |
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 |
