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net: sched: gred: prevent races when adding offloads to stats

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Naresh reports seeing a warning that gred is calling
u64_stats_update_begin() with preemption enabled.
Arnd points out it's coming from _bstats_update().

We should be holding the qdisc lock when writing
to stats, they are also updated from the datapath.

Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
Link: https://lore.kernel.org/all/CA+G9fYsTr9_r893+62u6UGD3dVaCE-kN9C-Apmb2m=hxjc1Cqg@mail.gmail.com/
Fixes: e49efd5288 ("net: sched: gred: support reporting stats from offloads")
Link: https://lore.kernel.org/r/20230113044137.1383067-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski 2023-01-12 20:41:37 -08:00
parent edb5b63e56
commit 339346d49a
1 changed files with 2 additions and 0 deletions
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2
net/sched/sch_gred.c
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@ -377,6 +377,7 @@ static int gred_offload_dump_stats(struct Qdisc *sch)
/* Even if driver returns failure adjust the stats - in case offload
* ended but driver still wants to adjust the values.
*/
sch_tree_lock(sch);
for (i = 0; i < MAX_DPs; i++) {
if (!table->tab[i])
continue;
@ -393,6 +394,7 @@ static int gred_offload_dump_stats(struct Qdisc *sch)
sch->qstats.overlimits += hw_stats->stats.qstats[i].overlimits;
}
_bstats_update(&sch->bstats, bytes, packets);
sch_tree_unlock(sch);
kfree(hw_stats);
return ret;