On Mon 30-10-17 16:10:09, Peter Zijlstra wrote: > On Mon, Oct 30, 2017 at 07:09:21PM +0900, Byungchul Park wrote: > > On Mon, Oct 30, 2017 at 09:22:03AM +0100, Michal Hocko wrote: > > > [Cc Byungchul. The original full report is > > > http://lkml.kernel.org/r/089e0825eec8955c1f055c83d476@xxxxxxxxxx] > > > > > > Could you have a look please? This smells like a false positive to me. > > > > +cc peterz@xxxxxxxxxxxxx > > > > Hello, > > > > IMHO, the false positive was caused by the lockdep_map of 'cpuhp_state' > > which couldn't distinguish between cpu-up and cpu-down. > > > > And it was solved with the following commit by Peter and Thomas: > > > > 5f4b55e10645b7371322c800a5ec745cab487a6c > > smp/hotplug: Differentiate the AP-work lockdep class between up and down > > > > Therefore, we can avoid the false positive on later than the commit. > > > > Peter and Thomas, could you confirm it? > > I can indeed confirm it's running old code; cpuhp_state is no more. Does this mean the below chain is no longer possible with the current linux-next (tip)? > However, that splat translates like: > > __cpuhp_setup_state() > #0 cpus_read_lock() > __cpuhp_setup_state_cpuslocked() > #1 mutex_lock(&cpuhp_state_mutex) > > > > __cpuhp_state_add_instance() > #2 mutex_lock(&cpuhp_state_mutex) this should be #1 right? > cpuhp_issue_call() > cpuhp_invoke_ap_callback() > #3 wait_for_completion() > > msr_device_create() > ... > #4 filename_create() > #3 complete() > > > > do_splice() > #4 file_start_write() > do_splice_from() > iter_file_splice_write() > #5 pipe_lock() > vfs_iter_write() > ... > #6 inode_lock() > > > > sys_fcntl() > do_fcntl() > shmem_fcntl() > #5 inode_lock() > shmem_wait_for_pins() > if (!scan) > lru_add_drain_all() > #0 cpus_read_lock() > > > > Which is an actual real deadlock, there is no mixing of up and down. thanks a lot, this made it more clear to me. It took a while to actually see 0 -> 1 -> 3 -> 4 -> 5 -> 0 cycle. I have only focused on lru_add_drain_all while it was holding the cpus lock. -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
