On Tue, 18 Sep 2007 12:30:52 +0200 Nadia Derbey <[EMAIL PROTECTED]> wrote:
> 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 > >>no locks held by X/5879. > >> [<c012bcb1>] down_write+0x15/0x50 > >> [<c01b53af>] do_shmat+0x235/0x3a0 > >> [<c0106be2>] sys_ipc+0x146/0x263 > >> [<c0102892>] sysenter_past_esp+0xa7/0xb5 > >> [<c0102856>] sysenter_past_esp+0x6b/0xb5 > >> ======================= > > > > > > Here's a bug: > > > > --- a/ipc/util.c~ipc-integrate-ipc_checkid-into-ipc_lock-fix-2 > > +++ a/ipc/util.c > > @@ -691,7 +691,7 @@ struct kern_ipc_perm *ipc_lock(struct ip > > rcu_read_unlock(); > > return ERR_PTR(-EINVAL); > > } > > - > > + rcu_read_unlock(); > > return out; > > } > > > > Andrew, > > Actually the rcu_read_lock is released in ipc_unlock(). I agree it should be, but it isn't. > So I think we > shouldn't add an rcu_read_unlock() before leaving ipc_lock(). > This is a part that has not changed since the ref code. > Well, it was an optimisation. spin_lock() implies rcu_read_lock(). That's a bit dirty and we might choose to not do that. Would be interested in knowing the locking rules in there. For example, this: /** * ipc_findkey - find a key in an ipc identifier set * @ids: Identifier set * @key: The key to find * * Requires ipc_ids.mutex locked. * Returns the LOCKED pointer to the ipc structure if found or NULL * if not. * If key is found ipc contains its ipc structure */ appears to be hopelessly out of date? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
