Commit 339346d4 authored by Jakub Kicinski's avatar Jakub Kicinski
Browse files

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



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: default avatarLinux Kernel Functional Testing <lkft@linaro.org>
Link: https://lore.kernel.org/all/CA+G9fYsTr9_r893+62u6UGD3dVaCE-kN9C-Apmb2m=hxjc1Cqg@mail.gmail.com/
Fixes: e49efd52 ("net: sched: gred: support reporting stats from offloads")
Link: https://lore.kernel.org/r/20230113044137.1383067-1-kuba@kernel.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent edb5b63e

net/sched/sch_gred.c

+2 −0
Original line number Diff line number Diff line
@@ -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;