diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/livepatch/shadow-vars.txt | 31 |
1 files changed, 22 insertions, 9 deletions
diff --git a/Documentation/livepatch/shadow-vars.txt b/Documentation/livepatch/shadow-vars.txt index 89c66634d600..9c7ae191641c 100644 --- a/Documentation/livepatch/shadow-vars.txt +++ b/Documentation/livepatch/shadow-vars.txt @@ -34,9 +34,13 @@ meta-data and shadow-data: - data[] - storage for shadow data It is important to note that the klp_shadow_alloc() and -klp_shadow_get_or_alloc() calls, described below, store a *copy* of the -data that the functions are provided. Callers should provide whatever -mutual exclusion is required of the shadow data. +klp_shadow_get_or_alloc() are zeroing the variable by default. +They also allow to call a custom constructor function when a non-zero +value is needed. Callers should provide whatever mutual exclusion +is required. + +Note that the constructor is called under klp_shadow_lock spinlock. It allows +to do actions that can be done only once when a new variable is allocated. * klp_shadow_get() - retrieve a shadow variable data pointer - search hashtable for <obj, id> pair @@ -47,7 +51,7 @@ mutual exclusion is required of the shadow data. - WARN and return NULL - if <obj, id> doesn't already exist - allocate a new shadow variable - - copy data into the new shadow variable + - initialize the variable using a custom constructor and data when provided - add <obj, id> to the global hashtable * klp_shadow_get_or_alloc() - get existing or alloc a new shadow variable @@ -56,7 +60,7 @@ mutual exclusion is required of the shadow data. - return existing shadow variable - if <obj, id> doesn't already exist - allocate a new shadow variable - - copy data into the new shadow variable + - initialize the variable using a custom constructor and data when provided - add <obj, id> pair to the global hashtable * klp_shadow_free() - detach and free a <obj, id> shadow variable @@ -107,7 +111,8 @@ struct sta_info *sta_info_alloc(struct ieee80211_sub_if_data *sdata, sta = kzalloc(sizeof(*sta) + hw->sta_data_size, gfp); /* Attach a corresponding shadow variable, then initialize it */ - ps_lock = klp_shadow_alloc(sta, PS_LOCK, NULL, sizeof(*ps_lock), gfp); + ps_lock = klp_shadow_alloc(sta, PS_LOCK, sizeof(*ps_lock), gfp, + NULL, NULL); if (!ps_lock) goto shadow_fail; spin_lock_init(ps_lock); @@ -148,16 +153,24 @@ shadow variables to parents already in-flight. For commit 1d147bfa6429, a good spot to allocate a shadow spinlock is inside ieee80211_sta_ps_deliver_wakeup(): +int ps_lock_shadow_ctor(void *obj, void *shadow_data, void *ctor_data) +{ + spinlock_t *lock = shadow_data; + + spin_lock_init(lock); + return 0; +} + #define PS_LOCK 1 void ieee80211_sta_ps_deliver_wakeup(struct sta_info *sta) { - DEFINE_SPINLOCK(ps_lock_fallback); spinlock_t *ps_lock; /* sync with ieee80211_tx_h_unicast_ps_buf */ ps_lock = klp_shadow_get_or_alloc(sta, PS_LOCK, - &ps_lock_fallback, sizeof(ps_lock_fallback), - GFP_ATOMIC); + sizeof(*ps_lock), GFP_ATOMIC, + ps_lock_shadow_ctor, NULL); + if (ps_lock) spin_lock(ps_lock); ... |