From: Frederic Weisbecker <frederic@kernel.org>
To: Yair Podemsky <ypodemsk@redhat.com>
Cc: linux@armlinux.org.uk, mpe@ellerman.id.au, npiggin@gmail.com,
christophe.leroy@csgroup.eu, hca@linux.ibm.com,
gor@linux.ibm.com, agordeev@linux.ibm.com,
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davem@davemloft.net, tglx@linutronix.de, mingo@redhat.com,
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akpm@linux-foundation.org, peterz@infradead.org, arnd@arndb.de,
keescook@chromium.org, paulmck@kernel.org, jpoimboe@kernel.org,
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juerg.haefliger@canonical.com, rmk+kernel@armlinux.org.uk,
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linux-mm@kvack.org, mtosatti@redhat.com, vschneid@redhat.com,
dhildenb@redhat.com, alougovs@redhat.com
Subject: Re: [PATCH 3/3] mm/mmu_gather: send tlb_remove_table_smp_sync IPI only to CPUs in kernel mode
Date: Wed, 5 Apr 2023 13:10:07 +0200 [thread overview]
Message-ID: <ZC1XD/sEJY+zRujE@lothringen> (raw)
In-Reply-To: <ZC1Q7uX4rNLg3vEg@lothringen>
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...
next prev parent reply other threads:[~2023-04-05 11:10 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-04 13:42 [PATCH 0/3] send tlb_remove_table_smp_sync IPI only to necessary CPUs Yair Podemsky
2023-04-04 13:42 ` [PATCH 1/3] arch: Introduce ARCH_HAS_CPUMASK_BITS Yair Podemsky
2023-04-04 13:47 ` David Hildenbrand
2023-04-04 13:42 ` [PATCH 2/3] mm/mmu_gather: send tlb_remove_table_smp_sync IPI only to MM CPUs Yair Podemsky
2023-04-04 14:57 ` Peter Zijlstra
2023-04-04 13:42 ` [PATCH 3/3] mm/mmu_gather: send tlb_remove_table_smp_sync IPI only to CPUs in kernel mode Yair Podemsky
2023-04-04 14:03 ` David Hildenbrand
2023-04-04 15:12 ` Peter Zijlstra
2023-04-04 16:00 ` Peter Zijlstra
2023-04-05 10:43 ` Frederic Weisbecker
2023-04-05 11:10 ` Frederic Weisbecker [this message]
2023-04-05 11:41 ` Peter Zijlstra
2023-04-05 12:00 ` David Hildenbrand
2023-04-05 12:05 ` Frederic Weisbecker
2023-04-05 12:31 ` Frederic Weisbecker
2023-04-05 12:45 ` Valentin Schneider
2023-04-06 13:38 ` Peter Zijlstra
2023-04-06 14:11 ` Valentin Schneider
2023-04-06 14:39 ` Peter Zijlstra
2023-04-05 19:45 ` Marcelo Tosatti
2023-04-05 19:52 ` Peter Zijlstra
2023-04-06 12:38 ` Marcelo Tosatti
2023-04-06 13:29 ` Peter Zijlstra
2023-04-06 14:04 ` Peter Zijlstra
2023-04-06 14:42 ` David Hildenbrand
2023-04-06 15:06 ` Peter Zijlstra
2023-04-06 15:02 ` Peter Zijlstra
2023-04-06 15:51 ` David Hildenbrand
2023-04-06 18:27 ` Peter Zijlstra
2023-04-19 11:30 ` David Hildenbrand
2023-04-19 11:39 ` Marcelo Tosatti
2023-04-05 19:43 ` Marcelo Tosatti
2023-04-05 19:54 ` Peter Zijlstra
2023-04-06 12:49 ` Marcelo Tosatti
2023-04-06 13:32 ` Peter Zijlstra
2023-04-19 11:01 ` Marcelo Tosatti
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