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Commit 71261956973ba9e0637848a5adb4a5819b4bae83

Authored by Paolo Valente
Committed by David S. Miller
1 parent 15c041759b
Exists in smarc-l5.0.0_1.0.0-ga and in 5 other branches imx_3.10.17_1.0.1_ga, imx_3.10.53_1.1.0_ga, imx_3.14.28_1.0.0_ga, smarc-imx_3.10.53_1.1.0_ga, smarc-imx_3.14.28_1.0.0_ga

pkt_sched: fix virtual-start-time update in QFQ 

If the old timestamps of a class, say cl, are stale when the class
becomes active, then QFQ may assign to cl a much higher start time
than the maximum value allowed. This may happen when QFQ assigns to
the start time of cl the finish time of a group whose classes are
characterized by a higher value of the ratio
max_class_pkt/weight_of_the_class with respect to that of
cl. Inserting a class with a too high start time into the bucket list
corrupts the data structure and may eventually lead to crashes.
This patch limits the maximum start time assigned to a class.

Signed-off-by: Paolo Valente <paolo.valente@unimore.it>
Signed-off-by: David S. Miller <davem@davemloft.net>

Showing 1 changed file with 4 additions and 1 deletions Side-by-side Diff

... ... @@ -865,7 +865,10 @@
865 865 if (mask) {
866 866 struct qfq_group *next = qfq_ffs(q, mask);
867 867 if (qfq_gt(roundedF, next->F)) {
868   - cl->S = next->F;
  868 + if (qfq_gt(limit, next->F))
  869 + cl->S = next->F;
  870 + else /* preserve timestamp correctness */
  871 + cl->S = limit;
869 872 return;
870 873 }
871 874 }