Andrew Morton wrote:
On Tue, 18 Sep 2007 13:17:28 +0400 Alexey Dobriyan <[email protected]> wrote:
I'm getting tons of this, and X fails to start
CONFIG_SYSVIPC=y
CONFIG_SYSVIPC_SYSCTL=y
# CONFIG_PREEMPT_NONE is not set
# CONFIG_PREEMPT_VOLUNTARY is not set
CONFIG_PREEMPT=y
CONFIG_PREEMPT_BKL=y
CONFIG_DEBUG_PREEMPT=y
BUG: sleeping function called from invalid context at kernel/rwsem.c:47
in_atomic():1, irqs_disabled():0
OK, this fixes the locking here:
--- a/ipc/util.c~ipc-integrate-ipc_checkid-into-ipc_lock-fix-2
+++ a/ipc/util.c
@@ -295,7 +295,6 @@ int ipc_addid(struct ipc_ids* ids, struc
spin_lock_init(&new->lock);
new->deleted = 0;
- rcu_read_lock();
spin_lock(&new->lock);
return id;
}
@@ -691,7 +690,7 @@ struct kern_ipc_perm *ipc_lock(struct ip
rcu_read_unlock();
return ERR_PTR(-EINVAL);
}
-
+ rcu_read_unlock();
return out;
}
Well, reviewing the code I found another place where the
rcu_read_unlock() was missing.
I'm so sorry for the inconvenience. It's true that I should have tested
with CONFIG_PREEMPT=y :-(
Now, the ltp tests pass even with this option set...
In attachment you'll find a patch thhat
1) adds the missing rcu_read_unlock()
2) replaces Andrew's fix with a new one: the rcu_read_lock() is now
taken in ipc_lock() / ipc_lock_by_ptr() and released in ipc_unlock(),
exactly as it was done in the ref code.
Regards,
Nadia
This patch fixes the missing rcu_read_(un)lock in the ipc code
Signed-off-by: Nadia Derbey <[email protected]>
---
ipc/util.c | 3 ++-
ipc/util.h | 4 +++-
2 files changed, 5 insertions(+), 2 deletions(-)
Index: linux-2.6.23-rc6-mm1/ipc/util.c
===================================================================
--- linux-2.6.23-rc6-mm1.orig/ipc/util.c 2007-09-18 16:39:43.000000000 +0200
+++ linux-2.6.23-rc6-mm1/ipc/util.c 2007-09-18 16:40:53.000000000 +0200
@@ -295,6 +295,7 @@ int ipc_addid(struct ipc_ids* ids, struc
spin_lock_init(&new->lock);
new->deleted = 0;
+ rcu_read_lock();
spin_lock(&new->lock);
return id;
}
@@ -690,7 +691,7 @@ struct kern_ipc_perm *ipc_lock(struct ip
rcu_read_unlock();
return ERR_PTR(-EINVAL);
}
- rcu_read_unlock();
+
return out;
}
Index: linux-2.6.23-rc6-mm1/ipc/util.h
===================================================================
--- linux-2.6.23-rc6-mm1.orig/ipc/util.h 2007-09-18 14:55:31.000000000 +0200
+++ linux-2.6.23-rc6-mm1/ipc/util.h 2007-09-18 16:41:37.000000000 +0200
@@ -141,12 +141,14 @@ static inline int ipc_checkid(struct ipc
static inline void ipc_lock_by_ptr(struct kern_ipc_perm *perm)
{
+ rcu_read_lock();
spin_lock(&perm->lock);
}
static inline void ipc_unlock(struct kern_ipc_perm *perm)
{
spin_unlock(&perm->lock);
+ rcu_read_unlock();
}
static inline struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids,
@@ -159,7 +161,7 @@ static inline struct kern_ipc_perm *ipc_
return out;
if (ipc_checkid(ids, out, id)) {
- spin_unlock(&out->lock);
+ ipc_unlock(out);
return ERR_PTR(-EIDRM);
}
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