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hwspinlock: add the 'in_atomic' API

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Add the 'in_atomic' mode which can be called from an atomic context.
This mode relies on the existing 'raw' mode (no lock, no preemption/irq
disabling) with the difference that the timeout is not based on jiffies
(jiffies won't increase when irq are disabled) but handled with
busy-waiting udelay() calls.

Signed-off-by: Fabien Dessenne <[email protected]>
Signed-off-by: Bjorn Andersson <[email protected]>
This commit is contained in:
Fabien Dessenne 2019-03-07 16:58:23 +01:00 • committed by Bjorn Andersson
commit 360aa640a5
3 changed files with 127 additions and 16 deletions
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43
drivers/hwspinlock/hwspinlock_core.c
View file

@ -9,6 +9,7 @@
#define pr_fmt(fmt) "%s: " fmt, __func__
#include <linux/delay.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/spinlock.h>
@ -23,6 +24,9 @@
#include "hwspinlock_internal.h"
/* retry delay used in atomic context */
#define HWSPINLOCK_RETRY_DELAY_US 100
/* radix tree tags */
#define HWSPINLOCK_UNUSED (0) /* tags an hwspinlock as unused */
@ -68,11 +72,11 @@ static DEFINE_MUTEX(hwspinlock_tree_lock);
* user need some time-consuming or sleepable operations under the hardware
* lock, they need one sleepable lock (like mutex) to protect the operations.
*
* If the mode is not HWLOCK_RAW, upon a successful return from this function,
* preemption (and possibly interrupts) is disabled, so the caller must not
* sleep, and is advised to release the hwspinlock as soon as possible. This is
* required in order to minimize remote cores polling on the hardware
* interconnect.
* If the mode is neither HWLOCK_IN_ATOMIC nor HWLOCK_RAW, upon a successful
* return from this function, preemption (and possibly interrupts) is disabled,
* so the caller must not sleep, and is advised to release the hwspinlock as
* soon as possible. This is required in order to minimize remote cores polling
* on the hardware interconnect.
*
* The user decides whether local interrupts are disabled or not, and if yes,
* whether he wants their previous state to be saved. It is up to the user
@ -112,6 +116,7 @@ int __hwspin_trylock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
ret = spin_trylock_irq(&hwlock->lock);
break;
case HWLOCK_RAW:
case HWLOCK_IN_ATOMIC:
ret = 1;
break;
default:
@ -136,6 +141,7 @@ int __hwspin_trylock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
spin_unlock_irq(&hwlock->lock);
break;
case HWLOCK_RAW:
case HWLOCK_IN_ATOMIC:
/* Nothing to do */
break;
default:
@ -179,11 +185,14 @@ EXPORT_SYMBOL_GPL(__hwspin_trylock);
* user need some time-consuming or sleepable operations under the hardware
* lock, they need one sleepable lock (like mutex) to protect the operations.
*
* If the mode is not HWLOCK_RAW, upon a successful return from this function,
* preemption is disabled (and possibly local interrupts, too), so the caller
* must not sleep, and is advised to release the hwspinlock as soon as possible.
* This is required in order to minimize remote cores polling on the
* hardware interconnect.
* If the mode is HWLOCK_IN_ATOMIC (called from an atomic context) the timeout
* is handled with busy-waiting delays, hence shall not exceed few msecs.
*
* If the mode is neither HWLOCK_IN_ATOMIC nor HWLOCK_RAW, upon a successful
* return from this function, preemption (and possibly interrupts) is disabled,
* so the caller must not sleep, and is advised to release the hwspinlock as
* soon as possible. This is required in order to minimize remote cores polling
* on the hardware interconnect.
*
* The user decides whether local interrupts are disabled or not, and if yes,
* whether he wants their previous state to be saved. It is up to the user
@ -198,7 +207,7 @@ int __hwspin_lock_timeout(struct hwspinlock *hwlock, unsigned int to,
int mode, unsigned long *flags)
{
int ret;
unsigned long expire;
unsigned long expire, atomic_delay = 0;
expire = msecs_to_jiffies(to) + jiffies;
@ -212,8 +221,15 @@ int __hwspin_lock_timeout(struct hwspinlock *hwlock, unsigned int to,
* The lock is already taken, let's check if the user wants
* us to try again
*/
if (time_is_before_eq_jiffies(expire))
return -ETIMEDOUT;
if (mode == HWLOCK_IN_ATOMIC) {
udelay(HWSPINLOCK_RETRY_DELAY_US);
atomic_delay += HWSPINLOCK_RETRY_DELAY_US;
if (atomic_delay > to * 1000)
return -ETIMEDOUT;
} else {
if (time_is_before_eq_jiffies(expire))
return -ETIMEDOUT;
}
/*
* Allow platform-specific relax handlers to prevent
@ -276,6 +292,7 @@ void __hwspin_unlock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
spin_unlock_irq(&hwlock->lock);
break;
case HWLOCK_RAW:
case HWLOCK_IN_ATOMIC:
/* Nothing to do */
break;
default: