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From: Johannes Berg To: Ben Greear , linux-wireless Cc: "Korenblit, Miriam Rachel" , linux-mm@kvack.org Date: Mon, 02 Mar 2026 09:07:04 +0100 In-Reply-To: References: <18c4bfed-caca-bef3-a139-63d7fa48940a@candelatech.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.3 (3.58.3-1.fc43) MIME-Version: 1.0 X-malware-bazaar: not-scanned X-Rspam-User: X-Rspamd-Queue-Id: 2F97D40004 X-Rspamd-Server: rspam08 X-Stat-Signature: ea49gd6ojpt3offre7eddpnhyoqo7noc X-HE-Tag: 1772438829-110641 X-HE-Meta: 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 Qh9tQujX G+y3W/RYTfeeXTLHHi1xRWm7c8H/xtmBgLh+smXIwU0+xmbyrhXJAj7dVB/nmlq8AQ4XXMRNm9NwLbvGhMy+f+h5+RdgXSs3YfMnpleWmEDu9sxFYNKv/E4fuuTX9DXgD04zff4UuXSKUeOtIVe1Q+R68pHbeq/8bturnJW2Xsp0usMvjoKdSkUD30pzd3O7FFquQUi2oHLQdb76jlonzqmXl+10Za35XpitKBHkxhovOdxM0WmOb2KCjWA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, 2026-03-01 at 07:38 -0800, Ben Greear wrote: > On 2/27/26 08:31, Ben Greear wrote: > > On 2/23/26 14:36, Ben Greear wrote: > > > Hello, > > >=20 > > > I hit a deadlock related to CMA mem allocation attempting to flush al= l work > > > while holding some wifi related mutex, and with a work-queue attempti= ng to process a wifi regdomain > > > work item.=C2=A0 I really don't see any good way to fix this, > > > it would seem that any code that was holding a mutex that could block= a work-queue > > > cannot safely allocate CMA memory?=C2=A0 Hopefully someone else has a= better idea. > >=20 > > I tried using a kthread to do the regulatory domain processing instead = of worker item, > > and that seems to have solved the problem.=C2=A0 If that seems reasonab= le approach to > > wifi stack folks, I can post a patch. >=20 > The other net/wireless work-item 'disconnect_work' also needs to be moved= to the kthread > for the same reason.... I don't think we want to use a kthread for this, it doesn't really make sense. Was this with lockdep? If so, it complain about anything? I'm having a hard time seeing why it would deadlock at all when wifi uses schedule_work() and therefore the system_percpu_wq, and __lru_add_drain_all() flushes lru_add_drain_work on mm_percpu_wq, and lru_add_and_bh_lrus_drain() doesn't really _seem_ to do anything related to RTNL etc.? I think we need a real explanation here rather than "if I randomly change this, it no longer appears". johannes