diff options
Diffstat (limited to 'include/linux/coresight.h')
| -rw-r--r-- | include/linux/coresight.h | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/include/linux/coresight.h b/include/linux/coresight.h index 365b28022c5b..74bcec526aa9 100644 --- a/include/linux/coresight.h +++ b/include/linux/coresight.h @@ -230,8 +230,15 @@ struct coresight_sysfs_link { * 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. - * @refcnt: keep track of what is in use. + * 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. + * @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 + * spinlock. * @orphan: true if the component has connections that haven't been linked. * @sysfs_sink_activated: 'true' when a sink has been selected for use via sysfs * by writing a 1 to the 'enable_sink' file. A sink can be @@ -257,7 +264,7 @@ struct coresight_device { struct csdev_access access; struct device dev; local_t mode; - atomic_t refcnt; + int refcnt; bool orphan; /* sink specific fields */ bool sysfs_sink_activated; |