Both __hwspin_trylock and __hwspin_unlock use hwlock->lock,
with a special annotation:
function will never sleep.
However, this requirement is not fulfilled on PREEMPT_RT.
Bjorn said:
: "will never sleep" comment expresses that the function can be called
: in atomic or irq context, not necessarily that it must not sleep.
This patch fixes these comments.
Suggested-by: Bjorn Andersson <andersson@xxxxxxxxxx>
Signed-off-by: Wen Yang <wen.yang@xxxxxxxxx>
Cc: Bjorn Andersson <andersson@xxxxxxxxxx>
Cc: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
Cc: Dave Young <dyoung@xxxxxxxxxx>
Cc: linux-remoteproc@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
Documentation/locking/hwspinlock.rst | 64 ++++++++++++++--------------
drivers/hwspinlock/hwspinlock_core.c | 25 +++++------
2 files changed, 46 insertions(+), 43 deletions(-)
diff --git a/Documentation/locking/hwspinlock.rst b/Documentation/locking/hwspinlock.rst
index 2ffaa3cbd63f..9d20823a21e7 100644
--- a/Documentation/locking/hwspinlock.rst
+++ b/Documentation/locking/hwspinlock.rst
@@ -103,14 +103,14 @@ Should be called from a process context (might sleep).
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.
-Upon a successful return from this function, preemption is disabled so
-the caller must not sleep, and is advised to release the hwspinlock as
-soon as possible, in order to minimize remote cores polling on the
-hardware interconnect.
+Upon a successful return from this function, preemption is disabled on
+non-PREEMPT_RT kernels, so the caller must not sleep, and is advised to
+release the hwspinlock as soon as possible, in order to minimize remote
+cores polling on the hardware interconnect.
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.
+The function will never sleep on a non-PREEMPT_RT kernel.
::
@@ -120,12 +120,12 @@ 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.
Upon a successful return from this function, preemption and the local
-interrupts are disabled, so the caller must not sleep, and is advised to
-release the hwspinlock as soon as possible.
+interrupts are disabled on non-PREEMPT_RT kernels, so the caller must not
+sleep, and is advised to release the hwspinlock as soon as possible.
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.
+The function will never sleep on a non-PREEMPT_RT kernel.
::
@@ -137,13 +137,13 @@ 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.
Upon a successful return from this function, preemption is disabled,
local interrupts are disabled and their previous state is saved at the
-given flags placeholder. The caller must not sleep, and is advised to
-release the hwspinlock as soon as possible.
+given flags placeholder on non-PREEMPT_RT kernels. The caller must not sleep,
+and is advised to release the hwspinlock as soon as possible.
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.
+The function will never sleep on a non-PREEMPT_RT kernel.
::
@@ -160,7 +160,7 @@ or sleepable operations under the hardware lock.
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.
+The function will never sleep on a non-PREEMPT_RT kernel.
::
@@ -176,7 +176,7 @@ 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.
+The function will never sleep on a non-PREEMPT_RT kernel.
::
@@ -186,14 +186,14 @@ The function will never sleep.
Attempt to lock a previously-assigned hwspinlock, but immediately fail if
it is already taken.
-Upon a successful return from this function, preemption is disabled so
-caller must not sleep, and is advised to release the hwspinlock as soon as
-possible, in order to minimize remote cores polling on the hardware
-interconnect.
+Upon a successful return from this function, preemption is disabled on
+non-PREEMPT_RT kernels so caller must not sleep and is advised to release
+the hwspinlock as soon as possible, in order to minimize remote cores polling
+on the hardware interconnect.
Returns 0 on success and an appropriate error code otherwise (most
notably -EBUSY if the hwspinlock was already taken).
-The function will never sleep.
+The function will never sleep on a non-PREEMPT_RT kernel.
::
@@ -204,13 +204,13 @@ Attempt to lock a previously-assigned hwspinlock, but immediately fail if
it is already taken.
Upon a successful return from this function, preemption and the local
-interrupts are disabled so caller must not sleep, and is advised to
-release the hwspinlock as soon as possible.
+interrupts are disabled on non-PREEMPT_RT kernels so caller must not sleep,
+and is advised to release the hwspinlock as soon as possible.
Returns 0 on success and an appropriate error code otherwise (most
notably -EBUSY if the hwspinlock was already taken).
-The function will never sleep.
+The function will never sleep on a non-PREEMPT_RT kernel.
::
@@ -221,12 +221,12 @@ it is already taken.
Upon a successful return from this function, preemption is disabled,
the local interrupts are disabled and their previous state is saved
-at the given flags placeholder. The caller must not sleep, and is advised
-to release the hwspinlock as soon as possible.
+at the given flags placeholder on non-PREEMPT_RT kernels. The caller must
+not sleep, and is advised to release the hwspinlock as soon as possible.
Returns 0 on success and an appropriate error code otherwise (most
notably -EBUSY if the hwspinlock was already taken).
-The function will never sleep.
+The function will never sleep on a non-PREEMPT_RT kernel.
::
@@ -241,7 +241,7 @@ or sleepable operations under the hardware lock.
Returns 0 on success and an appropriate error code otherwise (most
notably -EBUSY if the hwspinlock was already taken).
-The function will never sleep.
+The function will never sleep on a non-PREEMPT_RT kernel.
::
@@ -254,14 +254,14 @@ 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.
+The function will never sleep on a non-PREEMPT_RT kernel.
::
void hwspin_unlock(struct hwspinlock *hwlock);
Unlock a previously-locked hwspinlock. Always succeed, and can be called
-from any context (the function never sleeps).
+from any context (the function never sleeps on a non-PREEMPT_RT kernel).
.. note::
@@ -277,7 +277,8 @@ The caller should **never** unlock an hwspinlock which is already unlocked.
Doing so is considered a bug (there is no protection against this).
Upon a successful return from this function, preemption and local
-interrupts are enabled. This function will never sleep.
+interrupts are enabled on non-PREEMPT_RT kernels.
+This function will never sleep on a non-PREEMPT_RT kernel.
::
@@ -290,7 +291,8 @@ The caller should **never** unlock an hwspinlock which is already unlocked.
Doing so is considered a bug (there is no protection against this).
Upon a successful return from this function, preemption is reenabled,
and the state of the local interrupts is restored to the state saved at
-the given flags. This function will never sleep.
+the given flags on non-PREEMPT_RT kernels.
+This function will never sleep on a non-PREEMPT_RT kernel.
::
@@ -300,7 +302,7 @@ 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.
+This function will never sleep on a non-PREEMPT_RT kernel.
::
@@ -310,7 +312,7 @@ 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.
+This function will never sleep on a non-PREEMPT_RT kernel.
::
diff --git a/drivers/hwspinlock/hwspinlock_core.c b/drivers/hwspinlock/hwspinlock_core.c
index 6505261e6068..b602d6cf5e1b 100644
--- a/drivers/hwspinlock/hwspinlock_core.c
+++ b/drivers/hwspinlock/hwspinlock_core.c
@@ -73,10 +73,10 @@ static DEFINE_MUTEX(hwspinlock_tree_lock);
* lock, they need one sleepable lock (like mutex) to protect the operations.
*
* 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.
+ * return from this function, preemption (and possibly interrupts) is disabled
+ * on non-PREEMPT_RT kernels, 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
@@ -87,7 +87,7 @@ static DEFINE_MUTEX(hwspinlock_tree_lock);
* Returns: %0 if we successfully locked the hwspinlock or -EBUSY if
* the hwspinlock was already taken.
*
- * This function will never sleep.
+ * This function will never sleep on a non-PREEMPT_RT kernel.
*/
int __hwspin_trylock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
{
@@ -190,10 +190,10 @@ EXPORT_SYMBOL_GPL(__hwspin_trylock);
* 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.
+ * return from this function, preemption (and possibly interrupts) is disabled
+ * on non-PREEMPT_RT kernels, 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
@@ -204,7 +204,7 @@ EXPORT_SYMBOL_GPL(__hwspin_trylock);
* error code otherwise (most notably -ETIMEDOUT if the @hwlock is still
* busy after @timeout msecs).
*
- * The function will never sleep.
+ * The function will never sleep on a non-PREEMPT_RT kernel.
*/
int __hwspin_lock_timeout(struct hwspinlock *hwlock, unsigned int to,
int mode, unsigned long *flags)
@@ -253,7 +253,8 @@ EXPORT_SYMBOL_GPL(__hwspin_lock_timeout);
* @flags: previous caller's interrupt state to restore (if requested)
*
* This function will unlock a specific hwspinlock, enable preemption and
- * (possibly) enable interrupts or restore their previous state.
+ * (possibly) enable interrupts or restore their previous state on
+ * non-PREEMPT_RT kernels.
* @hwlock must be already locked before calling this function: it is a bug
* to call unlock on a @hwlock that is already unlocked.
*
@@ -263,7 +264,7 @@ EXPORT_SYMBOL_GPL(__hwspin_lock_timeout);
* same way users decide between spin_unlock, spin_unlock_irq and
* spin_unlock_irqrestore.
*
- * The function will never sleep.
+ * The function will never sleep on a non-PREEMPT_RT kernel.
*/
void __hwspin_unlock(struct hwspinlock *hwlock, int mode, unsigned long *flags)
{
--
2.25.1
