diff options
| author | Leo Yan <leo.yan@arm.com> | 2025-11-11 18:58:35 +0000 |
|---|---|---|
| committer | Suzuki K Poulose <suzuki.poulose@arm.com> | 2025-11-11 21:47:57 +0000 |
| commit | 693d1eaca940f277af24c74873ef2313816ff444 (patch) | |
| tree | b22b875c3f7ec205b1ccc9543feb32e79a67836d /include | |
| parent | b139702a889692ec30702534ebb1ae2b11ed1cbf (diff) | |
coresight: Change device mode to atomic type
The device mode is defined as local type. This type cannot promise
SMP-safe access.
Change to atomic type and impose relax ordering, which ensures the
SMP-safe synchronisation and the ordering between the mode setting and
relevant operations.
Fixes: 22fd532eaa0c ("coresight: etm3x: adding operation mode for etm_enable()")
Reviewed-by: Mike Leach <mike.leach@linaro.org>
Tested-by: James Clark <james.clark@linaro.org>
Signed-off-by: Leo Yan <leo.yan@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20251111-arm_coresight_power_management_fix-v6-1-f55553b6c8b3@arm.com
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/coresight.h | 25 |
1 files changed, 11 insertions, 14 deletions
diff --git a/include/linux/coresight.h b/include/linux/coresight.h index 56d0108658db..2b48be97fcd0 100644 --- a/include/linux/coresight.h +++ b/include/linux/coresight.h @@ -251,15 +251,11 @@ struct coresight_trace_id_map { * by @coresight_ops. * @access: Device i/o access abstraction for this device. * @dev: The device entity associated to this component. - * @mode: This tracer's mode, i.e sysFS, Perf or disabled. This is - * actually an 'enum cs_mode', but is stored in an atomic type. - * This is always accessed through local_read() and local_set(), - * but wherever it's done from within the Coresight device's lock, - * a non-atomic read would also work. This is the main point of - * synchronisation between code happening inside the sysfs mode's - * coresight_mutex and outside when running in Perf mode. A compare - * and exchange swap is done to atomically claim one mode or the - * other. + * @mode: The device mode, i.e sysFS, Perf or disabled. This is actually + * an 'enum cs_mode' but stored in an atomic type. Access is always + * through atomic APIs, ensuring SMP-safe synchronisation between + * racing from sysFS and Perf mode. A compare-and-exchange + * operation is done to atomically claim one mode or the other. * @refcnt: keep track of what is in use. Only access this outside of the * device's spinlock when the coresight_mutex held and mode == * CS_MODE_SYSFS. Otherwise it must be accessed from inside the @@ -288,7 +284,7 @@ struct coresight_device { const struct coresight_ops *ops; struct csdev_access access; struct device dev; - local_t mode; + atomic_t mode; int refcnt; bool orphan; /* sink specific fields */ @@ -624,13 +620,14 @@ static inline bool coresight_is_percpu_sink(struct coresight_device *csdev) static inline bool coresight_take_mode(struct coresight_device *csdev, enum cs_mode new_mode) { - return local_cmpxchg(&csdev->mode, CS_MODE_DISABLED, new_mode) == - CS_MODE_DISABLED; + int curr = CS_MODE_DISABLED; + + return atomic_try_cmpxchg_acquire(&csdev->mode, &curr, new_mode); } static inline enum cs_mode coresight_get_mode(struct coresight_device *csdev) { - return local_read(&csdev->mode); + return atomic_read_acquire(&csdev->mode); } static inline void coresight_set_mode(struct coresight_device *csdev, @@ -646,7 +643,7 @@ static inline void coresight_set_mode(struct coresight_device *csdev, WARN(new_mode != CS_MODE_DISABLED && current_mode != CS_MODE_DISABLED && current_mode != new_mode, "Device already in use\n"); - local_set(&csdev->mode, new_mode); + atomic_set_release(&csdev->mode, new_mode); } struct coresight_device *coresight_register(struct coresight_desc *desc); |