From: Steven Rostedt <rostedt@goodmis.org>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Ankur Arora <ankur.a.arora@oracle.com>,
linux-kernel@vger.kernel.org, tglx@linutronix.de,
peterz@infradead.org, torvalds@linux-foundation.org,
akpm@linux-foundation.org, luto@kernel.org, bp@alien8.de,
dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com,
juri.lelli@redhat.com, vincent.guittot@linaro.org,
willy@infradead.org, mgorman@suse.de, jpoimboe@kernel.org,
mark.rutland@arm.com, jgross@suse.com, andrew.cooper3@citrix.com,
bristot@kernel.org, mathieu.desnoyers@efficios.com,
glaubitz@physik.fu-berlin.de, anton.ivanov@cambridgegreys.com,
mattst88@gmail.com, krypton@ulrich-teichert.org,
David.Laight@aculab.com, richard@nod.at, jon.grimm@amd.com,
bharata@amd.com, boris.ostrovsky@oracle.com,
konrad.wilk@oracle.com
Subject: Re: [PATCH 00/30] PREEMPT_AUTO: support lazy rescheduling
Date: Wed, 21 Feb 2024 15:11:57 -0500 [thread overview]
Message-ID: <20240221151157.042c3291@gandalf.local.home> (raw)
In-Reply-To: <8f30ecd8-629b-414e-b6ea-b526b265b592@paulmck-laptop>
On Wed, 21 Feb 2024 11:41:47 -0800
"Paul E. McKenney" <paulmck@kernel.org> wrote:
> > I wonder if we can just see if the instruction pointer at preemption is at
> > something that was allocated? That is, if it __is_kernel(addr) returns
> > false, then we need to do more work. Of course that means modules will also
> > trigger this. We could check __is_module_text() but that does a bit more
> > work and may cause too much overhead. But who knows, if the module check is
> > only done if the __is_kernel() check fails, maybe it's not that bad.
>
> I do like very much that idea, but it requires that we be able to identify
> this instruction pointer perfectly, no matter what. It might also require
> that we be able to perfectly identify any IRQ return addresses as well,
> for example, if the preemption was triggered within an interrupt handler.
> And interrupts from softirq environments might require identifying an
> additional level of IRQ return address. The original IRQ might have
> interrupted a trampoline, and then after transitioning into softirq,
> another IRQ might also interrupt a trampoline, and this last IRQ handler
> might have instigated a preemption.
Note, softirqs still require a real interrupt to happen in order to preempt
executing code. Otherwise it should never be running from a trampoline.
>
> Are there additional levels or mechanisms requiring identifying
> return addresses?
Hmm, could we add to irq_enter_rcu()
__this_cpu_write(__rcu_ip, instruction_pointer(get_irq_regs()));
That is to save off were the ip was when it was interrupted.
Hmm, but it looks like the get_irq_regs() is set up outside of
irq_enter_rcu() :-(
I wonder how hard it would be to change all the architectures to pass in
pt_regs to irq_enter_rcu()? All the places it is called, the regs should be
available.
Either way, it looks like it will be a bit of work around the trampoline or
around RCU to get this efficiently done.
-- Steve
next prev parent reply other threads:[~2024-02-21 20:10 UTC|newest]
Thread overview: 157+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-13 5:55 [PATCH 00/30] PREEMPT_AUTO: support lazy rescheduling Ankur Arora
2024-02-13 5:55 ` [PATCH 01/30] preempt: introduce CONFIG_PREEMPT_AUTO Ankur Arora
2024-02-13 5:55 ` [PATCH 02/30] thread_info: selector for TIF_NEED_RESCHED[_LAZY] Ankur Arora
2024-02-19 15:16 ` Thomas Gleixner
2024-02-20 22:50 ` Ankur Arora
2024-02-21 17:05 ` Thomas Gleixner
2024-02-21 18:26 ` Steven Rostedt
2024-02-21 20:03 ` Thomas Gleixner
2024-02-13 5:55 ` [PATCH 03/30] thread_info: tif_need_resched() now takes resched_t as param Ankur Arora
2024-02-14 3:17 ` kernel test robot
2024-02-14 14:08 ` Mark Rutland
2024-02-15 4:08 ` Ankur Arora
2024-02-19 12:30 ` Mark Rutland
2024-02-20 22:09 ` Ankur Arora
2024-02-19 15:21 ` Thomas Gleixner
2024-02-20 22:21 ` Ankur Arora
2024-02-21 17:07 ` Thomas Gleixner
2024-02-21 21:22 ` Ankur Arora
2024-02-13 5:55 ` [PATCH 04/30] sched: make test_*_tsk_thread_flag() return bool Ankur Arora
2024-02-14 14:12 ` Mark Rutland
2024-02-15 2:04 ` Ankur Arora
2024-02-13 5:55 ` [PATCH 05/30] sched: *_tsk_need_resched() now takes resched_t as param Ankur Arora
2024-02-19 15:26 ` Thomas Gleixner
2024-02-20 22:37 ` Ankur Arora
2024-02-21 17:10 ` Thomas Gleixner
2024-02-13 5:55 ` [PATCH 06/30] entry: handle lazy rescheduling at user-exit Ankur Arora
2024-02-19 15:29 ` Thomas Gleixner
2024-02-20 22:38 ` Ankur Arora
2024-02-13 5:55 ` [PATCH 07/30] entry/kvm: handle lazy rescheduling at guest-entry Ankur Arora
2024-02-13 5:55 ` [PATCH 08/30] entry: irqentry_exit only preempts for TIF_NEED_RESCHED Ankur Arora
2024-02-13 5:55 ` [PATCH 09/30] sched: __schedule_loop() doesn't need to check for need_resched_lazy() Ankur Arora
2024-02-13 5:55 ` [PATCH 10/30] sched: separate PREEMPT_DYNAMIC config logic Ankur Arora
2024-02-13 5:55 ` [PATCH 11/30] sched: runtime preemption config under PREEMPT_AUTO Ankur Arora
2024-02-13 5:55 ` [PATCH 12/30] rcu: limit PREEMPT_RCU to full preemption " Ankur Arora
2024-02-13 5:55 ` [PATCH 13/30] rcu: fix header guard for rcu_all_qs() Ankur Arora
2024-02-13 5:55 ` [PATCH 14/30] preempt,rcu: warn on PREEMPT_RCU=n, preempt=full Ankur Arora
2024-02-13 5:55 ` [PATCH 15/30] rcu: handle quiescent states for PREEMPT_RCU=n, PREEMPT_COUNT=y Ankur Arora
2024-03-10 10:03 ` Joel Fernandes
2024-03-10 18:56 ` Paul E. McKenney
2024-03-11 0:48 ` Joel Fernandes
2024-03-11 3:56 ` Paul E. McKenney
2024-03-11 15:01 ` Joel Fernandes
2024-03-11 20:51 ` Ankur Arora
2024-03-11 22:12 ` Thomas Gleixner
2024-03-11 5:18 ` Ankur Arora
2024-03-11 15:25 ` Joel Fernandes
2024-03-11 19:12 ` Thomas Gleixner
2024-03-11 19:53 ` Paul E. McKenney
2024-03-11 20:29 ` Thomas Gleixner
2024-03-12 0:01 ` Paul E. McKenney
2024-03-12 0:08 ` Joel Fernandes
2024-03-12 3:16 ` Ankur Arora
2024-03-12 3:24 ` Joel Fernandes
2024-03-12 5:23 ` Ankur Arora
2024-02-13 5:55 ` [PATCH 16/30] rcu: force context-switch " Ankur Arora
2024-02-13 5:55 ` [PATCH 17/30] x86/thread_info: define TIF_NEED_RESCHED_LAZY Ankur Arora
2024-02-14 13:25 ` Mark Rutland
2024-02-14 20:31 ` Ankur Arora
2024-02-19 12:32 ` Mark Rutland
2024-02-13 5:55 ` [PATCH 18/30] sched: prepare for lazy rescheduling in resched_curr() Ankur Arora
2024-02-13 5:55 ` [PATCH 19/30] sched: default preemption policy for PREEMPT_AUTO Ankur Arora
2024-02-13 5:55 ` [PATCH 20/30] sched: handle idle preemption " Ankur Arora
2024-02-13 5:55 ` [PATCH 21/30] sched: schedule eagerly in resched_cpu() Ankur Arora
2024-02-13 5:55 ` [PATCH 22/30] sched/fair: refactor update_curr(), entity_tick() Ankur Arora
2024-02-13 5:55 ` [PATCH 23/30] sched/fair: handle tick expiry under lazy preemption Ankur Arora
2024-02-21 21:38 ` Steven Rostedt
2024-02-28 13:47 ` Juri Lelli
2024-02-29 6:43 ` Ankur Arora
2024-02-29 9:33 ` Juri Lelli
2024-02-29 23:54 ` Ankur Arora
2024-03-01 0:28 ` Paul E. McKenney
2024-02-13 5:55 ` [PATCH 24/30] sched: support preempt=none under PREEMPT_AUTO Ankur Arora
2024-02-13 5:55 ` [PATCH 25/30] sched: support preempt=full " Ankur Arora
2024-02-13 5:55 ` [PATCH 26/30] sched: handle preempt=voluntary " Ankur Arora
2024-03-03 1:08 ` Joel Fernandes
2024-03-05 8:11 ` Ankur Arora
2024-03-06 20:42 ` Joel Fernandes
2024-03-07 19:01 ` Paul E. McKenney
2024-03-08 0:15 ` Joel Fernandes
2024-03-08 0:42 ` Paul E. McKenney
2024-03-08 4:22 ` Ankur Arora
2024-03-08 21:33 ` Paul E. McKenney
2024-03-11 4:50 ` Ankur Arora
2024-03-11 19:26 ` Paul E. McKenney
2024-03-11 20:09 ` Ankur Arora
2024-03-11 20:23 ` Linus Torvalds
2024-03-11 21:03 ` Ankur Arora
2024-03-12 0:03 ` Paul E. McKenney
2024-03-12 12:14 ` Thomas Gleixner
2024-03-12 19:40 ` Paul E. McKenney
2024-03-08 3:49 ` Ankur Arora
2024-03-08 5:29 ` Joel Fernandes
2024-03-08 6:54 ` Juri Lelli
2024-03-11 5:34 ` Ankur Arora
2024-02-13 5:55 ` [PATCH 27/30] sched: latency warn for TIF_NEED_RESCHED_LAZY Ankur Arora
2024-02-13 5:55 ` [PATCH 28/30] tracing: support lazy resched Ankur Arora
2024-02-13 5:55 ` [PATCH 29/30] Documentation: tracing: add TIF_NEED_RESCHED_LAZY Ankur Arora
2024-02-21 21:43 ` Steven Rostedt
2024-02-21 23:22 ` Ankur Arora
2024-02-21 23:53 ` Steven Rostedt
2024-03-01 23:33 ` Joel Fernandes
2024-03-02 3:09 ` Ankur Arora
2024-03-03 19:32 ` Joel Fernandes
2024-02-13 5:55 ` [PATCH 30/30] osnoise: handle quiescent states for PREEMPT_RCU=n, PREEMPTION=y Ankur Arora
2024-02-13 9:47 ` [PATCH 00/30] PREEMPT_AUTO: support lazy rescheduling Geert Uytterhoeven
2024-02-13 21:46 ` Ankur Arora
2024-02-14 23:57 ` Paul E. McKenney
2024-02-15 2:03 ` Ankur Arora
2024-02-15 3:45 ` Paul E. McKenney
2024-02-15 19:28 ` Paul E. McKenney
2024-02-15 20:04 ` Thomas Gleixner
2024-02-15 20:54 ` Paul E. McKenney
2024-02-15 20:53 ` Ankur Arora
2024-02-15 20:55 ` Paul E. McKenney
2024-02-15 21:24 ` Ankur Arora
2024-02-15 22:54 ` Paul E. McKenney
2024-02-15 22:56 ` Paul E. McKenney
2024-02-16 0:45 ` Ankur Arora
2024-02-16 2:59 ` Paul E. McKenney
2024-02-17 0:55 ` Paul E. McKenney
2024-02-17 3:59 ` Ankur Arora
2024-02-18 18:17 ` Paul E. McKenney
2024-02-19 16:48 ` Paul E. McKenney
2024-02-21 18:19 ` Steven Rostedt
2024-02-21 19:41 ` Paul E. McKenney
2024-02-21 20:11 ` Steven Rostedt [this message]
2024-02-21 20:22 ` Paul E. McKenney
2024-02-22 15:50 ` Mark Rutland
2024-02-22 19:11 ` Paul E. McKenney
2024-02-23 11:05 ` Mark Rutland
2024-02-23 15:31 ` Paul E. McKenney
2024-03-02 1:16 ` Paul E. McKenney
2024-03-19 11:45 ` Tasks RCU, ftrace, and trampolines (was: Re: [PATCH 00/30] PREEMPT_AUTO: support lazy rescheduling) Mark Rutland
2024-03-19 23:33 ` Paul E. McKenney
2024-02-21 6:48 ` [PATCH 00/30] PREEMPT_AUTO: support lazy rescheduling Ankur Arora
2024-02-21 17:44 ` Paul E. McKenney
2024-02-16 0:45 ` Ankur Arora
2024-02-21 12:23 ` Raghavendra K T
2024-02-21 17:15 ` Thomas Gleixner
2024-02-21 17:27 ` Raghavendra K T
2024-02-21 21:16 ` Ankur Arora
2024-02-22 4:05 ` Raghavendra K T
2024-02-22 21:23 ` Thomas Gleixner
2024-02-23 3:14 ` Ankur Arora
2024-02-23 6:28 ` Raghavendra K T
2024-02-24 3:15 ` Raghavendra K T
2024-02-27 17:45 ` Ankur Arora
2024-02-22 13:04 ` Raghavendra K T
2024-04-23 15:21 ` Shrikanth Hegde
2024-04-23 16:13 ` Linus Torvalds
2024-04-26 7:46 ` Shrikanth Hegde
2024-04-26 19:00 ` Ankur Arora
2024-05-07 11:16 ` Shrikanth Hegde
2024-05-08 5:18 ` Ankur Arora
2024-05-15 14:31 ` Shrikanth Hegde
[not found] <draft-87a5o4go5i.ffs@tglx>
2024-02-19 15:54 ` Thomas Gleixner
2024-02-21 6:48 ` Ankur Arora
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