* [PATCH] CAPI: Silence lockdep warning on get_capi_appl_by_nr usage
@ 2010-10-16 11:14 Jan Kiszka
2010-10-17 10:25 ` Peter Zijlstra
0 siblings, 1 reply; 4+ messages in thread
From: Jan Kiszka @ 2010-10-16 11:14 UTC (permalink / raw)
To: David S. Miller
Cc: Linux Kernel Mailing List, i4ldeveloper, Linux Netdev List,
Karsten Keil
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
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH] CAPI: Silence lockdep warning on get_capi_appl_by_nr usage
2010-10-16 11:14 [PATCH] CAPI: Silence lockdep warning on get_capi_appl_by_nr usage Jan Kiszka
@ 2010-10-17 10:25 ` Peter Zijlstra
2010-10-17 15:18 ` [PATCH v2] " Jan Kiszka
0 siblings, 1 reply; 4+ messages in thread
From: Peter Zijlstra @ 2010-10-17 10:25 UTC (permalink / raw)
To: Jan Kiszka
Cc: David S. Miller, Linux Kernel Mailing List, i4ldeveloper,
Linux Netdev List, Karsten Keil
On Sat, 2010-10-16 at 13:14 +0200, Jan Kiszka wrote:
> + WARN_ON_ONCE(!mutex_is_locked(&capi_controller_lock));
Note there is also lockdep_assert_held() which will actually validate
that the current task is the owner.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH v2] CAPI: Silence lockdep warning on get_capi_appl_by_nr usage
2010-10-17 10:25 ` Peter Zijlstra
@ 2010-10-17 15:18 ` Jan Kiszka
2010-10-21 11:29 ` David Miller
0 siblings, 1 reply; 4+ messages in thread
From: Jan Kiszka @ 2010-10-17 15:18 UTC (permalink / raw)
To: David S. Miller
Cc: Linux Kernel Mailing List, i4ldeveloper, Linux Netdev List,
Karsten Keil, Peter Zijlstra
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>
---
v2:
- use lockdep_assert_held in favor of WARN_ON_ONCE(!mutex_is_locked)
as suggested by Peter
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..2b33b26 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)
+{
+ lockdep_assert_held(&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
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH v2] CAPI: Silence lockdep warning on get_capi_appl_by_nr usage
2010-10-17 15:18 ` [PATCH v2] " Jan Kiszka
@ 2010-10-21 11:29 ` David Miller
0 siblings, 0 replies; 4+ messages in thread
From: David Miller @ 2010-10-21 11:29 UTC (permalink / raw)
To: jan.kiszka; +Cc: linux-kernel, i4ldeveloper, netdev, isdn, peterz
From: Jan Kiszka <jan.kiszka@web.de>
Date: Sun, 17 Oct 2010 17:18:15 +0200
> 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>
Applied.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2010-10-16 11:14 [PATCH] CAPI: Silence lockdep warning on get_capi_appl_by_nr usage Jan Kiszka
2010-10-17 10:25 ` Peter Zijlstra
2010-10-17 15:18 ` [PATCH v2] " Jan Kiszka
2010-10-21 11:29 ` David Miller
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