[ Upstream commit 014077044e ]
When QMAN_FQ_FLAG_DYNAMIC_FQID is set, there's a race condition between
fq_table[fq->idx] state and freeing/allocating from the pool and
WARN_ON(fq_table[fq->idx]) in qman_create_fq() gets triggered.
Indeed, we can have:
Thread A Thread B
qman_destroy_fq() qman_create_fq()
qman_release_fqid()
qman_shutdown_fq()
gen_pool_free()
-- At this point, the fqid is available again --
qman_alloc_fqid()
-- so, we can get the just-freed fqid in thread B --
fq->fqid = fqid;
fq->idx = fqid * 2;
WARN_ON(fq_table[fq->idx]);
fq_table[fq->idx] = fq;
fq_table[fq->idx] = NULL;
And adding some logs between qman_release_fqid() and
fq_table[fq->idx] = NULL makes the WARN_ON() trigger a lot more.
To prevent that, ensure that fq_table[fq->idx] is set to NULL before
gen_pool_free() is called by using smp_wmb().
Fixes: c535e923bb ("soc/fsl: Introduce DPAA 1.x QMan device driver")
Signed-off-by: Richard Genoud <richard.genoud@bootlin.com>
Tested-by: CHAMPSEIX Thomas <thomas.champseix@alstomgroup.com>
Link: https://lore.kernel.org/r/20251223072549.397625-1-richard.genoud@bootlin.com
Signed-off-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
d288fbe652