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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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39
Documentation/hwspinlock.txt
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@ -151,6 +151,22 @@ notably -ETIMEDOUT if the hwspinlock is still busy after timeout msecs).
The function will never sleep.
::
int hwspin_lock_timeout_in_atomic(struct hwspinlock *hwlock, unsigned int to);
Lock a previously-assigned hwspinlock with a timeout limit (specified in
msecs). If the hwspinlock is already taken, the function will busy loop
waiting for it to be released, but give up when the timeout elapses.
This function shall be called only from an atomic context and the timeout
value shall not exceed a few msecs.
Returns 0 when successful and an appropriate error code otherwise (most
notably -ETIMEDOUT if the hwspinlock is still busy after timeout msecs).
The function will never sleep.
::
int hwspin_trylock(struct hwspinlock *hwlock);
@ -216,6 +232,19 @@ Returns 0 on success and an appropriate error code otherwise (most
notably -EBUSY if the hwspinlock was already taken).
The function will never sleep.
::
int hwspin_trylock_in_atomic(struct hwspinlock *hwlock);
Attempt to lock a previously-assigned hwspinlock, but immediately fail if
it is already taken.
This function shall be called only from an atomic context.
Returns 0 on success and an appropriate error code otherwise (most
notably -EBUSY if the hwspinlock was already taken).
The function will never sleep.
::
void hwspin_unlock(struct hwspinlock *hwlock);
@ -262,6 +291,16 @@ The caller should **never** unlock an hwspinlock which is already unlocked.
Doing so is considered a bug (there is no protection against this).
This function will never sleep.
::
void hwspin_unlock_in_atomic(struct hwspinlock *hwlock);
Unlock a previously-locked hwspinlock.
The caller should **never** unlock an hwspinlock which is already unlocked.
Doing so is considered a bug (there is no protection against this).
This function will never sleep.
::
int hwspin_lock_get_id(struct hwspinlock *hwlock);