From: Jesse Brandeburg <jesse.brandeburg@intel.com> To: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org>, linux-kernel@vger.kernel.org, intel-wired-lan@lists.osuosl.org, jbrandeb@kernel.org, "frederic@kernel.org" <frederic@kernel.org>, "juri.lelli@redhat.com" <juri.lelli@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>, abelits@marvell.com, Robin Murphy <robin.murphy@arm.com>, "linux-api@vger.kernel.org" <linux-api@vger.kernel.org>, "bhelgaas@google.com" <bhelgaas@google.com>, "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>, "rostedt@goodmis.org" <rostedt@goodmis.org>, "peterz@infradead.org" <peterz@infradead.org>, "davem@davemloft.net" <davem@davemloft.net>, "akpm@linux-foundation.org" <akpm@linux-foundation.org>, "sfr@canb.auug.org.au" <sfr@canb.auug.org.au>, "stephen@networkplumber.org" <stephen@networkplumber.org>, "rppt@linux.vnet.ibm.com" <rppt@linux.vnet.ibm.com>, "jinyuqi@huawei.com" <jinyuqi@huawei.com>, "zhangshaokun@hisilicon.com" <zhangshaokun@hisilicon.com>, netdev@vger.kernel.org, chris.friesen@windriver.com, Jesse Brandeburg <jesse.brandeburg@intel.com>, Nitesh Lal <nilal@redhat.com> Subject: [PATCH tip:irq/core v1] genirq: remove auto-set of the mask when setting the hint Date: Fri, 30 Apr 2021 19:18:32 -0700 [thread overview] Message-ID: <20210501021832.743094-1-jesse.brandeburg@intel.com> (raw) It was pointed out by Nitesh that the original work I did in 2014 to automatically set the interrupt affinity when requesting a mask is no longer necessary. The kernel has moved on and no longer has the original problem, BUT the original patch introduced a subtle bug when booting a system with reserved or excluded CPUs. Drivers calling this function with a mask value that included a CPU that was currently or in the future unavailable would generally not update the hint. I'm sure there are a million ways to solve this, but the simplest one is to just remove a little code that tries to force the affinity, as Nitesh has shown it fixes the bug and doesn't seem to introduce immediate side effects. While I'm here, introduce a kernel-doc for the hint function. Ref: https://lore.kernel.org/lkml/CAFki+L=_dd+JgAR12_eBPX0kZO2_6=1dGdgkwHE=u=K6chMeLQ@mail.gmail.com/ Cc: netdev@vger.kernel.org Fixes: 4fe7ffb7e17c ("genirq: Fix null pointer reference in irq_set_affinity_hint()") Fixes: e2e64a932556 ("genirq: Set initial affinity in irq_set_affinity_hint()") Reported-by: Nitesh Lal <nilal@redhat.com> Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com> --- !!! NOTE: Compile tested only, would appreciate feedback --- kernel/irq/manage.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c index e976c4927b25..a31df64662d5 100644 --- a/kernel/irq/manage.c +++ b/kernel/irq/manage.c @@ -456,6 +456,16 @@ int __irq_set_affinity(unsigned int irq, const struct cpumask *mask, bool force) return ret; } +/** + * irq_set_affinity_hint - set the hint for an irq + * @irq: Interrupt for which to set the hint + * @m: Mask to indicate which CPUs to suggest for the interrupt, use + * NULL here to indicate to clear the value. + * + * Use this function to recommend which CPU should handle the + * interrupt to any userspace that uses /proc/irq/nn/smp_affinity_hint + * in order to align interrupts. Pass NULL as the mask to clear the hint. + */ int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m) { unsigned long flags; @@ -465,9 +475,6 @@ int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m) return -EINVAL; desc->affinity_hint = m; irq_put_desc_unlock(desc, flags); - /* set the initial affinity to prevent every interrupt being on CPU0 */ - if (m) - __irq_set_affinity(irq, m, false); return 0; } EXPORT_SYMBOL_GPL(irq_set_affinity_hint); base-commit: 765822e1569a37aab5e69736c52d4ad4a289eba6 -- 2.30.2
WARNING: multiple messages have this Message-ID (diff)
From: Jesse Brandeburg <jesse.brandeburg@intel.com> To: intel-wired-lan@osuosl.org Subject: [Intel-wired-lan] [PATCH tip:irq/core v1] genirq: remove auto-set of the mask when setting the hint Date: Fri, 30 Apr 2021 19:18:32 -0700 [thread overview] Message-ID: <20210501021832.743094-1-jesse.brandeburg@intel.com> (raw) It was pointed out by Nitesh that the original work I did in 2014 to automatically set the interrupt affinity when requesting a mask is no longer necessary. The kernel has moved on and no longer has the original problem, BUT the original patch introduced a subtle bug when booting a system with reserved or excluded CPUs. Drivers calling this function with a mask value that included a CPU that was currently or in the future unavailable would generally not update the hint. I'm sure there are a million ways to solve this, but the simplest one is to just remove a little code that tries to force the affinity, as Nitesh has shown it fixes the bug and doesn't seem to introduce immediate side effects. While I'm here, introduce a kernel-doc for the hint function. Ref: https://lore.kernel.org/lkml/CAFki+L=_dd+JgAR12_eBPX0kZO2_6=1dGdgkwHE=u=K6chMeLQ at mail.gmail.com/ Cc: netdev at vger.kernel.org Fixes: 4fe7ffb7e17c ("genirq: Fix null pointer reference in irq_set_affinity_hint()") Fixes: e2e64a932556 ("genirq: Set initial affinity in irq_set_affinity_hint()") Reported-by: Nitesh Lal <nilal@redhat.com> Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com> --- !!! NOTE: Compile tested only, would appreciate feedback --- kernel/irq/manage.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c index e976c4927b25..a31df64662d5 100644 --- a/kernel/irq/manage.c +++ b/kernel/irq/manage.c @@ -456,6 +456,16 @@ int __irq_set_affinity(unsigned int irq, const struct cpumask *mask, bool force) return ret; } +/** + * irq_set_affinity_hint - set the hint for an irq + * @irq: Interrupt for which to set the hint + * @m: Mask to indicate which CPUs to suggest for the interrupt, use + * NULL here to indicate to clear the value. + * + * Use this function to recommend which CPU should handle the + * interrupt to any userspace that uses /proc/irq/nn/smp_affinity_hint + * in order to align interrupts. Pass NULL as the mask to clear the hint. + */ int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m) { unsigned long flags; @@ -465,9 +475,6 @@ int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m) return -EINVAL; desc->affinity_hint = m; irq_put_desc_unlock(desc, flags); - /* set the initial affinity to prevent every interrupt being on CPU0 */ - if (m) - __irq_set_affinity(irq, m, false); return 0; } EXPORT_SYMBOL_GPL(irq_set_affinity_hint); base-commit: 765822e1569a37aab5e69736c52d4ad4a289eba6 -- 2.30.2
next reply other threads:[~2021-05-01 2:18 UTC|newest] Thread overview: 71+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-05-01 2:18 Jesse Brandeburg [this message] 2021-05-01 2:18 ` [Intel-wired-lan] [PATCH tip:irq/core v1] genirq: remove auto-set of the mask when setting the hint Jesse Brandeburg 2021-05-04 12:15 ` Robin Murphy 2021-05-04 12:15 ` [Intel-wired-lan] " Robin Murphy 2021-05-04 14:29 ` Nitesh Lal 2021-05-04 14:29 ` [Intel-wired-lan] " Nitesh Lal 2021-05-04 16:23 ` Jesse Brandeburg 2021-05-04 16:23 ` [Intel-wired-lan] " Jesse Brandeburg 2021-05-17 16:57 ` Nitesh Lal 2021-05-17 16:57 ` [Intel-wired-lan] " Nitesh Lal 2021-05-17 17:26 ` Robin Murphy 2021-05-17 17:26 ` [Intel-wired-lan] " Robin Murphy 2021-05-17 18:08 ` Thomas Gleixner 2021-05-17 18:08 ` [Intel-wired-lan] " Thomas Gleixner 2021-05-17 18:50 ` Robin Murphy 2021-05-17 18:50 ` [Intel-wired-lan] " Robin Murphy 2021-05-17 19:08 ` Thomas Gleixner 2021-05-17 19:08 ` [Intel-wired-lan] " Thomas Gleixner 2021-05-17 19:43 ` Thomas Gleixner 2021-05-17 19:43 ` [Intel-wired-lan] " Thomas Gleixner 2021-05-17 20:18 ` Thomas Gleixner 2021-05-17 20:18 ` [Intel-wired-lan] " Thomas Gleixner 2021-05-17 18:21 ` Nitesh Lal 2021-05-17 18:21 ` [Intel-wired-lan] " Nitesh Lal 2021-05-17 19:47 ` Thomas Gleixner 2021-05-17 19:47 ` [Intel-wired-lan] " Thomas Gleixner 2021-05-17 21:13 ` Nitesh Lal 2021-05-17 21:13 ` [Intel-wired-lan] " Nitesh Lal 2021-05-17 20:48 ` Thomas Gleixner 2021-05-17 20:48 ` [Intel-wired-lan] " Thomas Gleixner 2021-05-17 22:44 ` Nitesh Lal 2021-05-17 22:44 ` [Intel-wired-lan] " Nitesh Lal 2021-05-18 0:03 ` Thomas Gleixner 2021-05-18 0:03 ` [Intel-wired-lan] " Thomas Gleixner 2021-05-18 0:23 ` Nitesh Lal 2021-05-18 0:23 ` [Intel-wired-lan] " Nitesh Lal 2021-05-20 21:57 ` Nitesh Lal 2021-05-20 21:57 ` [Intel-wired-lan] " Nitesh Lal 2021-05-21 0:03 ` Nitesh Lal 2021-05-21 0:03 ` [Intel-wired-lan] " Nitesh Lal 2021-05-21 11:56 ` Thomas Gleixner 2021-05-21 11:56 ` [Intel-wired-lan] " Thomas Gleixner 2021-05-21 12:03 ` [PATCH] genirq: Provide new interfaces for affinity hints Thomas Gleixner 2021-05-21 12:03 ` [Intel-wired-lan] " Thomas Gleixner 2021-05-21 15:45 ` Lijun Pan 2021-05-21 15:45 ` [Intel-wired-lan] " Lijun Pan 2021-05-21 21:45 ` Thomas Gleixner 2021-05-21 21:45 ` [Intel-wired-lan] " Thomas Gleixner 2021-05-21 16:13 ` Nitesh Lal 2021-05-21 16:13 ` [Intel-wired-lan] " Nitesh Lal 2021-05-21 21:48 ` Thomas Gleixner 2021-05-21 21:48 ` [Intel-wired-lan] " Thomas Gleixner 2021-06-04 20:35 ` Nitesh Lal 2021-06-04 20:35 ` [Intel-wired-lan] " Nitesh Lal 2021-05-27 10:03 ` Shung-Hsi Yu 2021-05-27 10:03 ` [Intel-wired-lan] " Shung-Hsi Yu 2021-05-27 10:21 ` Shung-Hsi Yu 2021-05-27 10:21 ` [Intel-wired-lan] " Shung-Hsi Yu 2021-05-27 13:06 ` Nitesh Lal 2021-05-27 13:06 ` [Intel-wired-lan] " Nitesh Lal 2021-05-28 7:20 ` Shung-Hsi Yu 2021-05-28 7:20 ` [Intel-wired-lan] " Shung-Hsi Yu 2021-06-07 17:00 ` Nitesh Lal 2021-06-07 17:00 ` [Intel-wired-lan] " Nitesh Lal 2021-06-14 16:12 ` Nitesh Lal 2021-06-14 16:12 ` [Intel-wired-lan] " Nitesh Lal 2021-05-21 13:46 ` [PATCH tip:irq/core v1] genirq: remove auto-set of the mask when setting the hint Nitesh Lal 2021-05-21 13:46 ` [Intel-wired-lan] " Nitesh Lal 2021-05-21 15:15 ` Thomas Gleixner 2021-05-21 15:15 ` [Intel-wired-lan] " Thomas Gleixner 2021-12-10 19:54 ` [tip: irq/core] genirq: Provide new interfaces for affinity hints tip-bot2 for Thomas Gleixner
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