user/sven/linux.git/kernel, branch v4.4.10

tracing: Don't display trigger file for events that can't be enabled

2016-05-11T09:21:13Z

commit 854145e0a8e9a05f7366d240e2f99d9c1ca6d6dd upstream. Currently register functions for events will be called through the 'reg' field of event class directly without any check when seting up triggers. Triggers for events that don't support register through debug fs (events under events/ftrace are for trace-cmd to read event format, and most of them don't have a register function except events/ftrace/functionx) can't be enabled at all, and an oops will be hit when setting up trigger for those events, so just not creating them is an easy way to avoid the oops. Link: http://lkml.kernel.org/r/1462275274-3911-1-git-send-email-chuhu@redhat.com Fixes: 85f2b08268c01 ("tracing: Add basic event trigger framework") Signed-off-by: Chunyu Hu Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman

locking/mcs: Fix mcs_spin_lock() ordering

2016-05-04T21:48:50Z

commit 920c720aa5aa3900a7f1689228fdfc2580a91e7e upstream. Similar to commit b4b29f94856a ("locking/osq: Fix ordering of node initialisation in osq_lock") the use of xchg_acquire() is fundamentally broken with MCS like constructs. Furthermore, it turns out we rely on the global transitivity of this operation because the unlock path observes the pointer with a READ_ONCE(), not an smp_load_acquire(). This is non-critical because the MCS code isn't actually used and mostly serves as documentation, a stepping stone to the more complex things we've build on top of the idea. Reported-by: Andrea Parri Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Will Deacon Fixes: 3552a07a9c4a ("locking/mcs: Use acquire/release semantics") Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

cgroup: make sure a parent css isn't freed before its children

2016-05-04T21:48:49Z

commit 8bb5ef79bc0f4016ecf79e8dce6096a3c63603e4 upstream. There are three subsystem callbacks in css shutdown path - css_offline(), css_released() and css_free(). Except for css_released(), cgroup core didn't guarantee the order of invocation. css_offline() or css_free() could be called on a parent css before its children. This behavior is unexpected and led to bugs in cpu and memory controller. The previous patch updated ordering for css_offline() which fixes the cpu controller issue. While there currently isn't a known bug caused by misordering of css_free() invocations, let's fix it too for consistency. css_free() ordering can be trivially fixed by moving putting of the parent css below css_free() invocation. Signed-off-by: Tejun Heo Cc: Peter Zijlstra Signed-off-by: Greg Kroah-Hartman

cgroup, cpuset: replace cpuset_post_attach_flush() with cgroup_subsys->post_attach callback

2016-05-04T21:48:49Z

commit 5cf1cacb49aee39c3e02ae87068fc3c6430659b0 upstream. Since e93ad19d0564 ("cpuset: make mm migration asynchronous"), cpuset kicks off asynchronous NUMA node migration if necessary during task migration and flushes it from cpuset_post_attach_flush() which is called at the end of __cgroup_procs_write(). This is to avoid performing migration with cgroup_threadgroup_rwsem write-locked which can lead to deadlock through dependency on kworker creation. memcg has a similar issue with charge moving, so let's convert it to an official callback rather than the current one-off cpuset specific function. This patch adds cgroup_subsys->post_attach callback and makes cpuset register cpuset_post_attach_flush() as its ->post_attach. The conversion is mostly one-to-one except that the new callback is called under cgroup_mutex. This is to guarantee that no other migration operations are started before ->post_attach callbacks are finished. cgroup_mutex is one of the outermost mutex in the system and has never been and shouldn't be a problem. We can add specialized synchronization around __cgroup_procs_write() but I don't think there's any noticeable benefit. Signed-off-by: Tejun Heo Cc: Li Zefan Cc: Johannes Weiner Cc: Michal Hocko Signed-off-by: Greg Kroah-Hartman

workqueue: fix ghost PENDING flag while doing MQ IO

2016-05-04T21:48:49Z

commit 346c09f80459a3ad97df1816d6d606169a51001a upstream. The bug in a workqueue leads to a stalled IO request in MQ ctx->rq_list with the following backtrace: [ 601.347452] INFO: task kworker/u129:5:1636 blocked for more than 120 seconds. [ 601.347574] Tainted: G O 4.4.5-1-storage+ #6 [ 601.347651] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 601.348142] kworker/u129:5 D ffff880803077988 0 1636 2 0x00000000 [ 601.348519] Workqueue: ibnbd_server_fileio_wq ibnbd_dev_file_submit_io_worker [ibnbd_server] [ 601.348999] ffff880803077988 ffff88080466b900 ffff8808033f9c80 ffff880803078000 [ 601.349662] ffff880807c95000 7fffffffffffffff ffffffff815b0920 ffff880803077ad0 [ 601.350333] ffff8808030779a0 ffffffff815b01d5 0000000000000000 ffff880803077a38 [ 601.350965] Call Trace: [ 601.351203] [] ? bit_wait+0x60/0x60 [ 601.351444] [] schedule+0x35/0x80 [ 601.351709] [] schedule_timeout+0x192/0x230 [ 601.351958] [] ? blk_flush_plug_list+0xc7/0x220 [ 601.352208] [] ? ktime_get+0x37/0xa0 [ 601.352446] [] ? bit_wait+0x60/0x60 [ 601.352688] [] io_schedule_timeout+0xa4/0x110 [ 601.352951] [] ? _raw_spin_unlock_irqrestore+0xe/0x10 [ 601.353196] [] bit_wait_io+0x1b/0x70 [ 601.353440] [] __wait_on_bit+0x5d/0x90 [ 601.353689] [] wait_on_page_bit+0xc0/0xd0 [ 601.353958] [] ? autoremove_wake_function+0x40/0x40 [ 601.354200] [] __filemap_fdatawait_range+0xe4/0x140 [ 601.354441] [] filemap_fdatawait_range+0x14/0x30 [ 601.354688] [] filemap_write_and_wait_range+0x3f/0x70 [ 601.354932] [] blkdev_fsync+0x1b/0x50 [ 601.355193] [] vfs_fsync_range+0x49/0xa0 [ 601.355432] [] blkdev_write_iter+0xca/0x100 [ 601.355679] [] __vfs_write+0xaa/0xe0 [ 601.355925] [] vfs_write+0xa9/0x1a0 [ 601.356164] [] kernel_write+0x38/0x50 The underlying device is a null_blk, with default parameters: queue_mode = MQ submit_queues = 1 Verification that nullb0 has something inflight: root@pserver8:~# cat /sys/block/nullb0/inflight 0 1 root@pserver8:~# find /sys/block/nullb0/mq/0/cpu* -name rq_list -print -exec cat {} \; ... /sys/block/nullb0/mq/0/cpu2/rq_list CTX pending: ffff8838038e2400 ... During debug it became clear that stalled request is always inserted in the rq_list from the following path: save_stack_trace_tsk + 34 blk_mq_insert_requests + 231 blk_mq_flush_plug_list + 281 blk_flush_plug_list + 199 wait_on_page_bit + 192 __filemap_fdatawait_range + 228 filemap_fdatawait_range + 20 filemap_write_and_wait_range + 63 blkdev_fsync + 27 vfs_fsync_range + 73 blkdev_write_iter + 202 __vfs_write + 170 vfs_write + 169 kernel_write + 56 So blk_flush_plug_list() was called with from_schedule == true. If from_schedule is true, that means that finally blk_mq_insert_requests() offloads execution of __blk_mq_run_hw_queue() and uses kblockd workqueue, i.e. it calls kblockd_schedule_delayed_work_on(). That means, that we race with another CPU, which is about to execute __blk_mq_run_hw_queue() work. Further debugging shows the following traces from different CPUs: CPU#0 CPU#1 ---------------------------------- ------------------------------- reqeust A inserted STORE hctx->ctx_map[0] bit marked kblockd_schedule...() returns 1 request B inserted STORE hctx->ctx_map[1] bit marked kblockd_schedule...() returns 0 *** WORK PENDING bit is cleared *** flush_busy_ctxs() is executed, but bit 1, set by CPU#1, is not observed As a result request B pended forever. This behaviour can be explained by speculative LOAD of hctx->ctx_map on CPU#0, which is reordered with clear of PENDING bit and executed _before_ actual STORE of bit 1 on CPU#1. The proper fix is an explicit full barrier , which guarantees that clear of PENDING bit is to be executed before all possible speculative LOADS or STORES inside actual work function. Signed-off-by: Roman Pen Cc: Gioh Kim Cc: Michael Wang Cc: Tejun Heo Cc: Jens Axboe Cc: linux-block@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman

futex: Acknowledge a new waiter in counter before plist

2016-05-04T21:48:43Z

commit fe1bce9e2107ba3a8faffe572483b6974201a0e6 upstream. Otherwise an incoming waker on the dest hash bucket can miss the waiter adding itself to the plist during the lockless check optimization (small window but still the correct way of doing this); similarly to the decrement counterpart. Suggested-by: Peter Zijlstra Signed-off-by: Davidlohr Bueso Cc: Davidlohr Bueso Cc: bigeasy@linutronix.de Cc: dvhart@infradead.org Link: http://lkml.kernel.org/r/1461208164-29150-1-git-send-email-dave@stgolabs.net Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

futex: Handle unlock_pi race gracefully

2016-05-04T21:48:43Z

commit 89e9e66ba1b3bde9d8ea90566c2aee20697ad681 upstream. If userspace calls UNLOCK_PI unconditionally without trying the TID -> 0 transition in user space first then the user space value might not have the waiters bit set. This opens the following race: CPU0 CPU1 uval = get_user(futex) lock(hb) lock(hb) futex |= FUTEX_WAITERS .... unlock(hb) cmpxchg(futex, uval, newval) So the cmpxchg fails and returns -EINVAL to user space, which is wrong because the futex value is valid. To handle this (yes, yet another) corner case gracefully, check for a flag change and retry. [ tglx: Massaged changelog and slightly reworked implementation ] Fixes: ccf9e6a80d9e ("futex: Make unlock_pi more robust") Signed-off-by: Sebastian Andrzej Siewior Cc: Davidlohr Bueso Cc: Darren Hart Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1460723739-5195-1-git-send-email-bigeasy@linutronix.de Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

sched/cgroup: Fix/cleanup cgroup teardown/init

2016-05-04T21:48:42Z

commit 2f5177f0fd7e531b26d54633be62d1d4cb94621c upstream. The CPU controller hasn't kept up with the various changes in the whole cgroup initialization / destruction sequence, and commit: 2e91fa7f6d45 ("cgroup: keep zombies associated with their original cgroups") caused it to explode. The reason for this is that zombies do not inhibit css_offline() from being called, but do stall css_released(). Now we tear down the cfs_rq structures on css_offline() but zombies can run after that, leading to use-after-free issues. The solution is to move the tear-down to css_released(), which guarantees nobody (including no zombies) is still using our cgroup. Furthermore, a few simple cleanups are possible too. There doesn't appear to be any point to us using css_online() (anymore?) so fold that in css_alloc(). And since cgroup code guarantees an RCU grace period between css_released() and css_free() we can forgo using call_rcu() and free the stuff immediately. Suggested-by: Tejun Heo Reported-by: Kazuki Yamaguchi Reported-by: Niklas Cassel Tested-by: Niklas Cassel Signed-off-by: Peter Zijlstra (Intel) Acked-by: Tejun Heo Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Fixes: 2e91fa7f6d45 ("cgroup: keep zombies associated with their original cgroups") Link: http://lkml.kernel.org/r/20160316152245.GY6344@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

perf: Cure event->pending_disable race

2016-04-20T06:42:14Z

commit 28a967c3a2f99fa3b5f762f25cb2a319d933571b upstream. Because event_sched_out() checks event->pending_disable _before_ actually disabling the event, it can happen that the event fires after it checks but before it gets disabled. This would leave event->pending_disable set and the queued irq_work will try and process it. However, if the event trigger was during schedule(), the event might have been de-scheduled by the time the irq_work runs, and perf_event_disable_local() will fail. Fix this by checking event->pending_disable _after_ we call event->pmu->del(). This depends on the latter being a compiler barrier, such that the compiler does not lift the load and re-creates the problem. Tested-by: Alexander Shishkin Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: dvyukov@google.com Cc: eranian@google.com Cc: oleg@redhat.com Cc: panand@redhat.com Cc: sasha.levin@oracle.com Cc: vince@deater.net Link: http://lkml.kernel.org/r/20160224174948.040469884@infradead.org Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman

perf: Do not double free

2016-04-20T06:42:14Z

commit 130056275ade730e7a79c110212c8815202773ee upstream. In case of: err_file: fput(event_file), we'll end up calling perf_release() which in turn will free the event. Do not then free the event _again_. Tested-by: Alexander Shishkin Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: dvyukov@google.com Cc: eranian@google.com Cc: oleg@redhat.com Cc: panand@redhat.com Cc: sasha.levin@oracle.com Cc: vince@deater.net Link: http://lkml.kernel.org/r/20160224174947.697350349@infradead.org Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman