Maneesh Soni wrote: > On Thu, May 17, 2007 at 05:04:23AM -0700, Greg KH wrote: >> On Wed, May 16, 2007 at 08:31:00PM +0200, Tejun Heo wrote: >>> sd->s_dentry updates made by dentry/inode reclamation are racy and can >>> lead to BUG() or oops. This is already fixed in -mm and the fix is >>> scheduled to be merged into upstream for 2.6.23 but the fix >>> reimplements sysfs dentry dropping and is too risky for -stable >>> kernels. >>> > > But was the synchronization fix tested by people facing the race? I still > don't understand the racy code path. The last google problem I saw had > s_dentry field as NULL.
Please take a look at the following message. http://article.gmane.org/gmane.linux.kernel/521729 I could reproduce both races on my test machine fairly reliable with parallel find, cat, mount/mount while repeatedly ins/rmmoding a libata driver. >>> This is an interim solution for -stable kernels. sysfs reclamation is >>> disabled by default and can be enabled by using sysfs.enable_reclaim >>> kernel parameter. Note that dentries are still created on demand, so >>> attribute and symlinks nodes aren't allocated on creation. They're >>> allocated on first lookup and deallocated when the sysfs node is >>> removed. >> Ick, this is going to kill memory on big boxes (s390 and others) and I >> don't really want to apply this it if at all possible. >> > At least not make it default. This might create boot issues with these > boxes. Which makes oopsing the default. Fun! :-) >> Maneesh, any other thoughts? >> > I actually wanted to investigate this oops but left it considering the > rework being done by Tejun. If this still make sense we can have some > more debug code stuffed there or get a crashdump (kdump) to get better > understanding of the race. The above message contains analysis of both races. I just ported the fixes. I have a different test machine now and can't reproduce the races with this one yet so I couldn't verify whether the patches actually fix the problem. I'll post the patches anyway. If anyone can reproduce these races, please verify the posted patches fix the problem. Thanks. -- tejun - 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/
