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charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: 4j7r7qg6skw8i56xn857s3i9mcpbghma X-Rspamd-Queue-Id: 33FB24001A X-HE-Tag: 1680724409-541098 X-HE-Meta: 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 51Nr+NAM 5Ra6xV9zffFpd9rXc+eLKEc3zti6TUy2NM11xkYRobOArB++XHpwcBLqTHSV+vePAGfppVgiNsyMnN5QwwwxSZilSnRV/K3j0GWo6rnBUQoy1M0GiFG27X3f5vuOkbIf69mMADsg4p/AT2in4YWWdpeaXAaibM2amu4R0kMc9mhtobA7+jla5z2HsBS4VQgGEQQuWDLQ/Gb/TExMx1BqyT5CTsLDZ0KNTRfxsM1Z1pxcobhKgvxgcqe2EAHTDK384C6Pgp1E25AoaefPvx66g6v+izuTaPyuWejrx X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Apr 05, 2023 at 04:45:32PM -0300, Marcelo Tosatti wrote: > On Wed, Apr 05, 2023 at 01:10:07PM +0200, Frederic Weisbecker wrote: > > On Wed, Apr 05, 2023 at 12:44:04PM +0200, Frederic Weisbecker wrote: > > > On Tue, Apr 04, 2023 at 04:42:24PM +0300, Yair Podemsky wrote: > > > > + int state = atomic_read(&ct->state); > > > > + /* will return true only for cpus in kernel space */ > > > > + return state & CT_STATE_MASK == CONTEXT_KERNEL; > > > > +} > > > > > > Also note that this doesn't stricly prevent userspace from being interrupted. > > > You may well observe the CPU in kernel but it may receive the IPI later after > > > switching to userspace. > > > > > > We could arrange for avoiding that with marking ct->state with a pending work bit > > > to flush upon user entry/exit but that's a bit more overhead so I first need to > > > know about your expectations here, ie: can you tolerate such an occasional > > > interruption or not? > > > > Bah, actually what can we do to prevent from that racy IPI? Not much I fear... > > Use a different mechanism other than an IPI to ensure in progress > __get_free_pages_fast() has finished execution. > > Isnt this codepath slow path enough that it can use > synchronize_rcu_expedited? To actually hit this path you're doing something really dodgy.