Eric Lee / smarc-ti-linux-kernel

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Commit 01f8fa4f01d8362358eb90e412bd7ae18a3ec1ad

Authored by Thomas Gleixner
1 parent 81cef0fe19
Exists in master and in 13 other branches dlt-processor-sdk-linux-03.00.00.04, processor-sdk-linux-02.00.01, smarc-ti-linux-3.15.y, smarc-ti-lsk-linux-4.1.y, smarct3x-processor-sdk-04.01.00.06, smarct3x-processor-sdk-linux-02.00.01, smarct3x-processor-sdk-linux-03.00.00.04, smarct4x-800-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-04.01.00.06, smarct4x-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-linux-03.00.00.04, ti-linux-3.15.y, ti-lsk-linux-4.1.y

genirq: Allow forcing cpu affinity of interrupts 

The current implementation of irq_set_affinity() refuses rightfully to
route an interrupt to an offline cpu.

But there is a special case, where this is actually desired. Some of
the ARM SoCs have per cpu timers which require setting the affinity
during cpu startup where the cpu is not yet in the online mask.

If we can't do that, then the local timer interrupt for the about to
become online cpu is routed to some random online cpu.

The developers of the affected machines tried to work around that
issue, but that results in a massive mess in that timer code.

We have a yet unused argument in the set_affinity callbacks of the irq
chips, which I added back then for a similar reason. It was never
required so it got not used. But I'm happy that I never removed it.

That allows us to implement a sane handling of the above scenario. So
the affected SoC drivers can add the required force handling to their
interrupt chip, switch the timer code to irq_force_affinity() and
things just work.

This does not affect any existing user of irq_set_affinity().

Tagged for stable to allow a simple fix of the affected SoC clock
event drivers.

Reported-and-tested-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Tomasz Figa <t.figa@samsung.com>,
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>,
Cc: Kukjin Kim <kgene.kim@samsung.com>
Cc: linux-arm-kernel@lists.infradead.org,
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20140416143315.717251504@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Showing 4 changed files with 43 additions and 14 deletions Side-by-side Diff

arch/mips/cavium-octeon/octeon-irq.c
Diff comments   View file @ 01f8fa4
... ... @@ -635,7 +635,7 @@
635 635 cpumask_clear(&new_affinity);
636 636 cpumask_set_cpu(cpumask_first(cpu_online_mask), &new_affinity);
637 637 }
638   - __irq_set_affinity_locked(data, &new_affinity);
  638 + irq_set_affinity_locked(data, &new_affinity, false);
639 639 }
640 640  
641 641 static int octeon_irq_ciu_set_affinity(struct irq_data *data,
include/linux/interrupt.h
Diff comments   View file @ 01f8fa4
... ... @@ -203,7 +203,40 @@
203 203  
204 204 extern cpumask_var_t irq_default_affinity;
205 205  
206   -extern int irq_set_affinity(unsigned int irq, const struct cpumask *cpumask);
  206 +/* Internal implementation. Use the helpers below */
  207 +extern int __irq_set_affinity(unsigned int irq, const struct cpumask *cpumask,
  208 + bool force);
  209 +
  210 +/**
  211 + * irq_set_affinity - Set the irq affinity of a given irq
  212 + * @irq: Interrupt to set affinity
  213 + * @mask: cpumask
  214 + *
  215 + * Fails if cpumask does not contain an online CPU
  216 + */
  217 +static inline int
  218 +irq_set_affinity(unsigned int irq, const struct cpumask *cpumask)
  219 +{
  220 + return __irq_set_affinity(irq, cpumask, false);
  221 +}
  222 +
  223 +/**
  224 + * irq_force_affinity - Force the irq affinity of a given irq
  225 + * @irq: Interrupt to set affinity
  226 + * @mask: cpumask
  227 + *
  228 + * Same as irq_set_affinity, but without checking the mask against
  229 + * online cpus.
  230 + *
  231 + * Solely for low level cpu hotplug code, where we need to make per
  232 + * cpu interrupts affine before the cpu becomes online.
  233 + */
  234 +static inline int
  235 +irq_force_affinity(unsigned int irq, const struct cpumask *cpumask)
  236 +{
  237 + return __irq_set_affinity(irq, cpumask, true);
  238 +}
  239 +
207 240 extern int irq_can_set_affinity(unsigned int irq);
208 241 extern int irq_select_affinity(unsigned int irq);
209 242  
... ... @@ -394,7 +394,8 @@
394 394  
395 395 extern void irq_cpu_online(void);
396 396 extern void irq_cpu_offline(void);
397   -extern int __irq_set_affinity_locked(struct irq_data *data, const struct cpumask *cpumask);
  397 +extern int irq_set_affinity_locked(struct irq_data *data,
  398 + const struct cpumask *cpumask, bool force);
398 399  
399 400 #if defined(CONFIG_SMP) && defined(CONFIG_GENERIC_PENDING_IRQ)
400 401 void irq_move_irq(struct irq_data *data);
... ... @@ -180,7 +180,7 @@
180 180 struct irq_chip *chip = irq_data_get_irq_chip(data);
181 181 int ret;
182 182  
183   - ret = chip->irq_set_affinity(data, mask, false);
  183 + ret = chip->irq_set_affinity(data, mask, force);
184 184 switch (ret) {
185 185 case IRQ_SET_MASK_OK:
186 186 cpumask_copy(data->affinity, mask);
... ... @@ -192,7 +192,8 @@
192 192 return ret;
193 193 }
194 194  
195   -int __irq_set_affinity_locked(struct irq_data *data, const struct cpumask *mask)
  195 +int irq_set_affinity_locked(struct irq_data *data, const struct cpumask *mask,
  196 + bool force)
196 197 {
197 198 struct irq_chip *chip = irq_data_get_irq_chip(data);
198 199 struct irq_desc *desc = irq_data_to_desc(data);
... ... @@ -202,7 +203,7 @@
202 203 return -EINVAL;
203 204  
204 205 if (irq_can_move_pcntxt(data)) {
205   - ret = irq_do_set_affinity(data, mask, false);
  206 + ret = irq_do_set_affinity(data, mask, force);
206 207 } else {
207 208 irqd_set_move_pending(data);
208 209 irq_copy_pending(desc, mask);
... ... @@ -217,13 +218,7 @@
217 218 return ret;
218 219 }
219 220  
220   -/**
221   - * irq_set_affinity - Set the irq affinity of a given irq
222   - * @irq: Interrupt to set affinity
223   - * @mask: cpumask
224   - *
225   - */
226   -int irq_set_affinity(unsigned int irq, const struct cpumask *mask)
  221 +int __irq_set_affinity(unsigned int irq, const struct cpumask *mask, bool force)
227 222 {
228 223 struct irq_desc *desc = irq_to_desc(irq);
229 224 unsigned long flags;
... ... @@ -233,7 +228,7 @@
233 228 return -EINVAL;
234 229  
235 230 raw_spin_lock_irqsave(&desc->lock, flags);
236   - ret = __irq_set_affinity_locked(irq_desc_get_irq_data(desc), mask);
  231 + ret = irq_set_affinity_locked(irq_desc_get_irq_data(desc), mask, force);
237 232 raw_spin_unlock_irqrestore(&desc->lock, flags);
238 233 return ret;
239 234 }