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Subject[PATCH] CAPI: Silence lockdep warning on get_capi_appl_by_nr usage
As long as we hold capi_controller_lock, we can safely access
capi_applications without RCU protection as no one can modify the
application list underneath us. Introduce an RCU-free
__get_capi_appl_by_nr for this purpose. This silences lockdep warnings
on suspicious rcu_dereference usage.

Signed-off-by: Jan Kiszka <jan.kiszka@web.de>
---
drivers/isdn/capi/kcapi.c | 19 ++++++++++++++-----
1 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/isdn/capi/kcapi.c b/drivers/isdn/capi/kcapi.c
index 2648d39..2c535d8 100644
--- a/drivers/isdn/capi/kcapi.c
+++ b/drivers/isdn/capi/kcapi.c
@@ -99,6 +99,16 @@ static inline struct capi_ctr *get_capi_ctr_by_nr(u16 contr)
return capi_controller[contr - 1];
}

+static inline struct capi20_appl *__get_capi_appl_by_nr(u16 applid)
+{
+ WARN_ON_ONCE(!mutex_is_locked(&capi_controller_lock));
+
+ if (applid - 1 >= CAPI_MAXAPPL)
+ return NULL;
+
+ return capi_applications[applid - 1];
+}
+
static inline struct capi20_appl *get_capi_appl_by_nr(u16 applid)
{
if (applid - 1 >= CAPI_MAXAPPL)
@@ -186,10 +196,9 @@ static void notify_up(u32 contr)
ctr->state = CAPI_CTR_RUNNING;

for (applid = 1; applid <= CAPI_MAXAPPL; applid++) {
- ap = get_capi_appl_by_nr(applid);
- if (!ap)
- continue;
- register_appl(ctr, applid, &ap->rparam);
+ ap = __get_capi_appl_by_nr(applid);
+ if (ap)
+ register_appl(ctr, applid, &ap->rparam);
}

wake_up_interruptible_all(&ctr->state_wait_queue);
@@ -216,7 +225,7 @@ static void ctr_down(struct capi_ctr *ctr, int new_state)
memset(ctr->serial, 0, sizeof(ctr->serial));

for (applid = 1; applid <= CAPI_MAXAPPL; applid++) {
- ap = get_capi_appl_by_nr(applid);
+ ap = __get_capi_appl_by_nr(applid);
if (ap)
capi_ctr_put(ctr);
}
--
1.7.1

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