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2014-05-14softirq: make migrate disable/enable conditioned on softirq_nestcnt transitionNicholas Mc Guire
This patch removes the recursive calls to migrate_disable/enable in local_bh_disable/enable the softirq-local-lock.patch introduces local_bh_disable/enable wich decrements/increments the current->softirq_nestcnt and disable/enables migration as well. as softirq_nestcnt (include/linux/sched.h conditioned on CONFIG_PREEMPT_RT_BASE) already is tracking the nesting level of the recursive calls to local_bh_disable/enable (all in kernel/softirq.c) - no need to do it twice. migrate_disable/enable thus can be conditionsed on softirq_nestcnt making a transition from 0-1 to disable migration and 1-0 to re-enable it. No change of functional behavior, this does noticably reduce the observed nesting level of migrate_disable/enable Signed-off-by: Nicholas Mc Guire <der.herr@hofr.at> Reviewed-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
2014-05-14softirq: Adapt NOHZ softirq pending check to new RT schemeThomas Gleixner
We can't rely on ksoftirqd anymore and we need to check the tasks which run a particular softirq and if such a task is pi blocked ignore the other pending bits of that task as well. Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14API cleanup - use local_lock not __local_lock for softNicholas Mc Guire
trivial API cleanup - kernel/softirq.c was mimiking local_lock. No change of functional behavior Signed-off-by: Nicholas Mc Guire <der.herr@hofr.at> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
2014-05-14softirq: Split softirq locksThomas Gleixner
The 3.x RT series removed the split softirq implementation in favour of pushing softirq processing into the context of the thread which raised it. Though this prevents us from handling the various softirqs at different priorities. Now instead of reintroducing the split softirq threads we split the locks which serialize the softirq processing. If a softirq is raised in context of a thread, then the softirq is noted on a per thread field, if the thread is in a bh disabled region. If the softirq is raised from hard interrupt context, then the bit is set in the flag field of ksoftirqd and ksoftirqd is invoked. When a thread leaves a bh disabled region, then it tries to execute the softirqs which have been raised in its own context. It acquires the per softirq / per cpu lock for the softirq and then checks, whether the softirq is still pending in the per cpu local_softirq_pending() field. If yes, it runs the softirq. If no, then some other task executed it already. This allows for zero config softirq elevation in the context of user space tasks or interrupt threads. Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14softirq: Split handling functionThomas Gleixner
Split out the inner handling function, so RT can reuse it. Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14softirq: Make serving softirqs a task flagThomas Gleixner
Avoid the percpu softirq_runner pointer magic by using a task flag. Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14softirq: Init softirq local lock after per cpu section is set upSteven Rostedt
I discovered this bug when booting 3.4-rt on my powerpc box. It crashed with the following report: ------------[ cut here ]------------ kernel BUG at /work/rt/stable-rt.git/kernel/rtmutex_common.h:75! Oops: Exception in kernel mode, sig: 5 [#1] PREEMPT SMP NR_CPUS=64 NUMA PA Semi PWRficient Modules linked in: NIP: c0000000004aa03c LR: c0000000004aa01c CTR: c00000000009b2ac REGS: c00000003e8d7950 TRAP: 0700 Not tainted (3.4.11-test-rt19) MSR: 9000000000029032 <SF,HV,EE,ME,IR,DR,RI> CR: 24000082 XER: 20000000 SOFTE: 0 TASK = c00000003e8fdcd0[11] 'ksoftirqd/1' THREAD: c00000003e8d4000 CPU: 1 GPR00: 0000000000000001 c00000003e8d7bd0 c000000000d6cbb0 0000000000000000 GPR04: c00000003e8fdcd0 0000000000000000 0000000024004082 c000000000011454 GPR08: 0000000000000000 0000000080000001 c00000003e8fdcd1 0000000000000000 GPR12: 0000000024000084 c00000000fff0280 ffffffffffffffff 000000003ffffad8 GPR16: ffffffffffffffff 000000000072c798 0000000000000060 0000000000000000 GPR20: 0000000000642741 000000000072c858 000000003ffffaf0 0000000000000417 GPR24: 000000000072dcd0 c00000003e7ff990 0000000000000000 0000000000000001 GPR28: 0000000000000000 c000000000792340 c000000000ccec78 c000000001182338 NIP [c0000000004aa03c] .wakeup_next_waiter+0x44/0xb8 LR [c0000000004aa01c] .wakeup_next_waiter+0x24/0xb8 Call Trace: [c00000003e8d7bd0] [c0000000004aa01c] .wakeup_next_waiter+0x24/0xb8 (unreliable) [c00000003e8d7c60] [c0000000004a0320] .rt_spin_lock_slowunlock+0x8c/0xe4 [c00000003e8d7ce0] [c0000000004a07cc] .rt_spin_unlock+0x54/0x64 [c00000003e8d7d60] [c0000000000636bc] .__thread_do_softirq+0x130/0x174 [c00000003e8d7df0] [c00000000006379c] .run_ksoftirqd+0x9c/0x1a4 [c00000003e8d7ea0] [c000000000080b68] .kthread+0xa8/0xb4 [c00000003e8d7f90] [c00000000001c2f8] .kernel_thread+0x54/0x70 Instruction dump: 60000000 e86d01c8 38630730 4bff7061 60000000 ebbf0008 7c7c1b78 e81d0040 7fe00278 7c000074 7800d182 68000001 <0b000000> e88d01c8 387d0010 38840738 The rtmutex_common.h:75 is: rt_mutex_top_waiter(struct rt_mutex *lock) { struct rt_mutex_waiter *w; w = plist_first_entry(&lock->wait_list, struct rt_mutex_waiter, list_entry); BUG_ON(w->lock != lock); return w; } Where the waiter->lock is corrupted. I saw various other random bugs that all had to with the softirq lock and plist. As plist needs to be initialized before it is used I investigated how this lock is initialized. It's initialized with: void __init softirq_early_init(void) { local_irq_lock_init(local_softirq_lock); } Where: #define local_irq_lock_init(lvar) \ do { \ int __cpu; \ for_each_possible_cpu(__cpu) \ spin_lock_init(&per_cpu(lvar, __cpu).lock); \ } while (0) As the softirq lock is a local_irq_lock, which is a per_cpu lock, the initialization is done to all per_cpu versions of the lock. But lets look at where the softirq_early_init() is called from. In init/main.c: start_kernel() /* * Interrupts are still disabled. Do necessary setups, then * enable them */ softirq_early_init(); tick_init(); boot_cpu_init(); page_address_init(); printk(KERN_NOTICE "%s", linux_banner); setup_arch(&command_line); mm_init_owner(&init_mm, &init_task); mm_init_cpumask(&init_mm); setup_command_line(command_line); setup_nr_cpu_ids(); setup_per_cpu_areas(); smp_prepare_boot_cpu(); /* arch-specific boot-cpu hooks */ One of the first things that is called is the initialization of the softirq lock. But if you look further down, we see the per_cpu areas have not been set up yet. Thus initializing a local_irq_lock() before the per_cpu section is set up, may not work as it is initializing the per cpu locks before the per cpu exists. By moving the softirq_early_init() right after setup_per_cpu_areas(), the kernel boots fine. Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Cc: Clark Williams <clark@redhat.com> Cc: John Kacur <jkacur@redhat.com> Cc: Carsten Emde <cbe@osadl.org> Cc: vomlehn@texas.net Link: http://lkml.kernel.org/r/1349362924.6755.18.camel@gandalf.local.home Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14softirq: Check preemption after reenabling interruptsThomas Gleixner
raise_softirq_irqoff() disables interrupts and wakes the softirq daemon, but after reenabling interrupts there is no preemption check, so the execution of the softirq thread might be delayed arbitrarily. In principle we could add that check to local_irq_enable/restore, but that's overkill as the rasie_softirq_irqoff() sections are the only ones which show this behaviour. Reported-by: Carsten Emde <cbe@osadl.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable-rt@vger.kernel.org
2014-05-14perf: Make swevent hrtimer run in irq instead of softirqYong Zhang
Otherwise we get a deadlock like below: [ 1044.042749] BUG: scheduling while atomic: ksoftirqd/21/141/0x00010003 [ 1044.042752] INFO: lockdep is turned off. [ 1044.042754] Modules linked in: [ 1044.042757] Pid: 141, comm: ksoftirqd/21 Tainted: G W 3.4.0-rc2-rt3-23676-ga723175-dirty #29 [ 1044.042759] Call Trace: [ 1044.042761] <IRQ> [<ffffffff8107d8e5>] __schedule_bug+0x65/0x80 [ 1044.042770] [<ffffffff8168978c>] __schedule+0x83c/0xa70 [ 1044.042775] [<ffffffff8106bdd2>] ? prepare_to_wait+0x32/0xb0 [ 1044.042779] [<ffffffff81689a5e>] schedule+0x2e/0xa0 [ 1044.042782] [<ffffffff81071ebd>] hrtimer_wait_for_timer+0x6d/0xb0 [ 1044.042786] [<ffffffff8106bb30>] ? wake_up_bit+0x40/0x40 [ 1044.042790] [<ffffffff81071f20>] hrtimer_cancel+0x20/0x40 [ 1044.042794] [<ffffffff8111da0c>] perf_swevent_cancel_hrtimer+0x3c/0x50 [ 1044.042798] [<ffffffff8111da31>] task_clock_event_stop+0x11/0x40 [ 1044.042802] [<ffffffff8111da6e>] task_clock_event_del+0xe/0x10 [ 1044.042805] [<ffffffff8111c568>] event_sched_out+0x118/0x1d0 [ 1044.042809] [<ffffffff8111c649>] group_sched_out+0x29/0x90 [ 1044.042813] [<ffffffff8111ed7e>] __perf_event_disable+0x18e/0x200 [ 1044.042817] [<ffffffff8111c343>] remote_function+0x63/0x70 [ 1044.042821] [<ffffffff810b0aae>] generic_smp_call_function_single_interrupt+0xce/0x120 [ 1044.042826] [<ffffffff81022bc7>] smp_call_function_single_interrupt+0x27/0x40 [ 1044.042831] [<ffffffff8168d50c>] call_function_single_interrupt+0x6c/0x80 [ 1044.042833] <EOI> [<ffffffff811275b0>] ? perf_event_overflow+0x20/0x20 [ 1044.042840] [<ffffffff8168b970>] ? _raw_spin_unlock_irq+0x30/0x70 [ 1044.042844] [<ffffffff8168b976>] ? _raw_spin_unlock_irq+0x36/0x70 [ 1044.042848] [<ffffffff810702e2>] run_hrtimer_softirq+0xc2/0x200 [ 1044.042853] [<ffffffff811275b0>] ? perf_event_overflow+0x20/0x20 [ 1044.042857] [<ffffffff81045265>] __do_softirq_common+0xf5/0x3a0 [ 1044.042862] [<ffffffff81045c3d>] __thread_do_softirq+0x15d/0x200 [ 1044.042865] [<ffffffff81045dda>] run_ksoftirqd+0xfa/0x210 [ 1044.042869] [<ffffffff81045ce0>] ? __thread_do_softirq+0x200/0x200 [ 1044.042873] [<ffffffff81045ce0>] ? __thread_do_softirq+0x200/0x200 [ 1044.042877] [<ffffffff8106b596>] kthread+0xb6/0xc0 [ 1044.042881] [<ffffffff8168b97b>] ? _raw_spin_unlock_irq+0x3b/0x70 [ 1044.042886] [<ffffffff8168d994>] kernel_thread_helper+0x4/0x10 [ 1044.042889] [<ffffffff8107d98c>] ? finish_task_switch+0x8c/0x110 [ 1044.042894] [<ffffffff8168b97b>] ? _raw_spin_unlock_irq+0x3b/0x70 [ 1044.042897] [<ffffffff8168bd5d>] ? retint_restore_args+0xe/0xe [ 1044.042900] [<ffffffff8106b4e0>] ? kthreadd+0x1e0/0x1e0 [ 1044.042902] [<ffffffff8168d990>] ? gs_change+0xb/0xb Signed-off-by: Yong Zhang <yong.zhang0@gmail.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Steven Rostedt <rostedt@goodmis.org> Link: http://lkml.kernel.org/r/1341476476-5666-1-git-send-email-yong.zhang0@gmail.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2014-05-14rt: rwsem/rwlock: lockdep annotationsThomas Gleixner
rwlocks and rwsems on RT do not allow multiple readers. Annotate the lockdep acquire functions accordingly. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable-rt@vger.kernel.org
2014-05-14lockdep: Selftest: Only do hardirq context test for raw spinlockYong Zhang
On -rt there is no softirq context any more and rwlock is sleepable, disable softirq context test and rwlock+irq test. Signed-off-by: Yong Zhang <yong.zhang0@gmail.com> Cc: Yong Zhang <yong.zhang@windriver.com> Link: http://lkml.kernel.org/r/1334559716-18447-3-git-send-email-yong.zhang0@gmail.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14crypto: Convert crypto notifier chain to SRCUPeter Zijlstra
The crypto notifier deadlocks on RT. Though this can be a real deadlock on mainline as well due to fifo fair rwsems. The involved parties here are: [ 82.172678] swapper/0 S 0000000000000001 0 1 0 0x00000000 [ 82.172682] ffff88042f18fcf0 0000000000000046 ffff88042f18fc80 ffffffff81491238 [ 82.172685] 0000000000011cc0 0000000000011cc0 ffff88042f18c040 ffff88042f18ffd8 [ 82.172688] 0000000000011cc0 0000000000011cc0 ffff88042f18ffd8 0000000000011cc0 [ 82.172689] Call Trace: [ 82.172697] [<ffffffff81491238>] ? _raw_spin_unlock_irqrestore+0x6c/0x7a [ 82.172701] [<ffffffff8148fd3f>] schedule+0x64/0x66 [ 82.172704] [<ffffffff8148ec6b>] schedule_timeout+0x27/0xd0 [ 82.172708] [<ffffffff81043c0c>] ? unpin_current_cpu+0x1a/0x6c [ 82.172713] [<ffffffff8106e491>] ? migrate_enable+0x12f/0x141 [ 82.172716] [<ffffffff8148fbbd>] wait_for_common+0xbb/0x11f [ 82.172719] [<ffffffff810709f2>] ? try_to_wake_up+0x182/0x182 [ 82.172722] [<ffffffff8148fc96>] wait_for_completion_interruptible+0x1d/0x2e [ 82.172726] [<ffffffff811debfd>] crypto_wait_for_test+0x49/0x6b [ 82.172728] [<ffffffff811ded32>] crypto_register_alg+0x53/0x5a [ 82.172730] [<ffffffff811ded6c>] crypto_register_algs+0x33/0x72 [ 82.172734] [<ffffffff81ad7686>] ? aes_init+0x12/0x12 [ 82.172737] [<ffffffff81ad76ea>] aesni_init+0x64/0x66 [ 82.172741] [<ffffffff81000318>] do_one_initcall+0x7f/0x13b [ 82.172744] [<ffffffff81ac4d34>] kernel_init+0x199/0x22c [ 82.172747] [<ffffffff81ac44ef>] ? loglevel+0x31/0x31 [ 82.172752] [<ffffffff814987c4>] kernel_thread_helper+0x4/0x10 [ 82.172755] [<ffffffff81491574>] ? retint_restore_args+0x13/0x13 [ 82.172759] [<ffffffff81ac4b9b>] ? start_kernel+0x3ca/0x3ca [ 82.172761] [<ffffffff814987c0>] ? gs_change+0x13/0x13 [ 82.174186] cryptomgr_test S 0000000000000001 0 41 2 0x00000000 [ 82.174189] ffff88042c971980 0000000000000046 ffffffff81d74830 0000000000000292 [ 82.174192] 0000000000011cc0 0000000000011cc0 ffff88042c96eb80 ffff88042c971fd8 [ 82.174195] 0000000000011cc0 0000000000011cc0 ffff88042c971fd8 0000000000011cc0 [ 82.174195] Call Trace: [ 82.174198] [<ffffffff8148fd3f>] schedule+0x64/0x66 [ 82.174201] [<ffffffff8148ec6b>] schedule_timeout+0x27/0xd0 [ 82.174204] [<ffffffff81043c0c>] ? unpin_current_cpu+0x1a/0x6c [ 82.174206] [<ffffffff8106e491>] ? migrate_enable+0x12f/0x141 [ 82.174209] [<ffffffff8148fbbd>] wait_for_common+0xbb/0x11f [ 82.174212] [<ffffffff810709f2>] ? try_to_wake_up+0x182/0x182 [ 82.174215] [<ffffffff8148fc96>] wait_for_completion_interruptible+0x1d/0x2e [ 82.174218] [<ffffffff811e4883>] cryptomgr_notify+0x280/0x385 [ 82.174221] [<ffffffff814943de>] notifier_call_chain+0x6b/0x98 [ 82.174224] [<ffffffff8108a11c>] ? rt_down_read+0x10/0x12 [ 82.174227] [<ffffffff810677cd>] __blocking_notifier_call_chain+0x70/0x8d [ 82.174230] [<ffffffff810677fe>] blocking_notifier_call_chain+0x14/0x16 [ 82.174234] [<ffffffff811dd272>] crypto_probing_notify+0x24/0x50 [ 82.174236] [<ffffffff811dd7a1>] crypto_alg_mod_lookup+0x3e/0x74 [ 82.174238] [<ffffffff811dd949>] crypto_alloc_base+0x36/0x8f [ 82.174241] [<ffffffff811e9408>] cryptd_alloc_ablkcipher+0x6e/0xb5 [ 82.174243] [<ffffffff811dd591>] ? kzalloc.clone.5+0xe/0x10 [ 82.174246] [<ffffffff8103085d>] ablk_init_common+0x1d/0x38 [ 82.174249] [<ffffffff8103852a>] ablk_ecb_init+0x15/0x17 [ 82.174251] [<ffffffff811dd8c6>] __crypto_alloc_tfm+0xc7/0x114 [ 82.174254] [<ffffffff811e0caa>] ? crypto_lookup_skcipher+0x1f/0xe4 [ 82.174256] [<ffffffff811e0dcf>] crypto_alloc_ablkcipher+0x60/0xa5 [ 82.174258] [<ffffffff811e5bde>] alg_test_skcipher+0x24/0x9b [ 82.174261] [<ffffffff8106d96d>] ? finish_task_switch+0x3f/0xfa [ 82.174263] [<ffffffff811e6b8e>] alg_test+0x16f/0x1d7 [ 82.174267] [<ffffffff811e45ac>] ? cryptomgr_probe+0xac/0xac [ 82.174269] [<ffffffff811e45d8>] cryptomgr_test+0x2c/0x47 [ 82.174272] [<ffffffff81061161>] kthread+0x7e/0x86 [ 82.174275] [<ffffffff8106d9dd>] ? finish_task_switch+0xaf/0xfa [ 82.174278] [<ffffffff814987c4>] kernel_thread_helper+0x4/0x10 [ 82.174281] [<ffffffff81491574>] ? retint_restore_args+0x13/0x13 [ 82.174284] [<ffffffff810610e3>] ? __init_kthread_worker+0x8c/0x8c [ 82.174287] [<ffffffff814987c0>] ? gs_change+0x13/0x13 [ 82.174329] cryptomgr_probe D 0000000000000002 0 47 2 0x00000000 [ 82.174332] ffff88042c991b70 0000000000000046 ffff88042c991bb0 0000000000000006 [ 82.174335] 0000000000011cc0 0000000000011cc0 ffff88042c98ed00 ffff88042c991fd8 [ 82.174338] 0000000000011cc0 0000000000011cc0 ffff88042c991fd8 0000000000011cc0 [ 82.174338] Call Trace: [ 82.174342] [<ffffffff8148fd3f>] schedule+0x64/0x66 [ 82.174344] [<ffffffff814901ad>] __rt_mutex_slowlock+0x85/0xbe [ 82.174347] [<ffffffff814902d2>] rt_mutex_slowlock+0xec/0x159 [ 82.174351] [<ffffffff81089c4d>] rt_mutex_fastlock.clone.8+0x29/0x2f [ 82.174353] [<ffffffff81490372>] rt_mutex_lock+0x33/0x37 [ 82.174356] [<ffffffff8108a0f2>] __rt_down_read+0x50/0x5a [ 82.174358] [<ffffffff8108a11c>] ? rt_down_read+0x10/0x12 [ 82.174360] [<ffffffff8108a11c>] rt_down_read+0x10/0x12 [ 82.174363] [<ffffffff810677b5>] __blocking_notifier_call_chain+0x58/0x8d [ 82.174366] [<ffffffff810677fe>] blocking_notifier_call_chain+0x14/0x16 [ 82.174369] [<ffffffff811dd272>] crypto_probing_notify+0x24/0x50 [ 82.174372] [<ffffffff811debd6>] crypto_wait_for_test+0x22/0x6b [ 82.174374] [<ffffffff811decd3>] crypto_register_instance+0xb4/0xc0 [ 82.174377] [<ffffffff811e9b76>] cryptd_create+0x378/0x3b6 [ 82.174379] [<ffffffff811de512>] ? __crypto_lookup_template+0x5b/0x63 [ 82.174382] [<ffffffff811e4545>] cryptomgr_probe+0x45/0xac [ 82.174385] [<ffffffff811e4500>] ? crypto_alloc_pcomp+0x1b/0x1b [ 82.174388] [<ffffffff81061161>] kthread+0x7e/0x86 [ 82.174391] [<ffffffff8106d9dd>] ? finish_task_switch+0xaf/0xfa [ 82.174394] [<ffffffff814987c4>] kernel_thread_helper+0x4/0x10 [ 82.174398] [<ffffffff81491574>] ? retint_restore_args+0x13/0x13 [ 82.174401] [<ffffffff810610e3>] ? __init_kthread_worker+0x8c/0x8c [ 82.174403] [<ffffffff814987c0>] ? gs_change+0x13/0x13 cryptomgr_test spawns the cryptomgr_probe thread from the notifier call. The probe thread fires the same notifier as the test thread and deadlocks on the rwsem on RT. Now this is a potential deadlock in mainline as well, because we have fifo fair rwsems. If another thread blocks with a down_write() on the notifier chain before the probe thread issues the down_read() it will block the probe thread and the whole party is dead locked. Signed-off-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14net: Add a mutex around devnet_rename_seqSebastian Andrzej Siewior
On RT write_seqcount_begin() disables preemption and device_rename() allocates memory with GFP_KERNEL and grabs later the sysfs_mutex mutex. Serialize with a mutex and add use the non preemption disabling __write_seqcount_begin(). To avoid writer starvation, let the reader grab the mutex and release it when it detects a writer in progress. This keeps the normal case (no reader on the fly) fast. [ tglx: Instead of replacing the seqcount by a mutex, add the mutex ] Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14net: Use local_bh_disable in netif_rx_ni()Thomas Gleixner
This code triggers the new WARN in __raise_softirq_irqsoff() though it actually looks at the softirq pending bit and calls into the softirq code, but that fits not well with the context related softirq model of RT. It's correct on mainline though, but going through local_bh_disable/enable here is not going to hurt badly. Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14net: netfilter: Serialize xt_write_recseq sections on RTThomas Gleixner
The netfilter code relies only on the implicit semantics of local_bh_disable() for serializing wt_write_recseq sections. RT breaks that and needs explicit serialization here. Reported-by: Peter LaDow <petela@gocougs.wsu.edu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable-rt@vger.kernel.org
2014-05-14net: ip_send_unicast_reply: add missing local serializationNicholas Mc Guire
in response to the oops in ip_output.c:ip_send_unicast_reply under high network load with CONFIG_PREEMPT_RT_FULL=y, reported by Sami Pietikainen <Sami.Pietikainen@wapice.com>, this patch adds local serialization in ip_send_unicast_reply. from ip_output.c: /* * Generic function to send a packet as reply to another packet. * Used to send some TCP resets/acks so far. * * Use a fake percpu inet socket to avoid false sharing and contention. */ static DEFINE_PER_CPU(struct inet_sock, unicast_sock) = { ... which was added in commit be9f4a44 in linux-stable. The git log, wich introduced the PER_CPU unicast_sock, states: <snip> commit be9f4a44e7d41cee50ddb5f038fc2391cbbb4046 Author: Eric Dumazet <edumazet@google.com> Date: Thu Jul 19 07:34:03 2012 +0000 ipv4: tcp: remove per net tcp_sock tcp_v4_send_reset() and tcp_v4_send_ack() use a single socket per network namespace. This leads to bad behavior on multiqueue NICS, because many cpus contend for the socket lock and once socket lock is acquired, extra false sharing on various socket fields slow down the operations. To better resist to attacks, we use a percpu socket. Each cpu can run without contention, using appropriate memory (local node) <snip> The per-cpu here thus is assuming exclusivity serializing per cpu - so the use of get_cpu_ligh introduced in net-use-cpu-light-in-ip-send-unicast-reply.patch, which droped the preempt_disable in favor of a migrate_disable is probably wrong as this only handles the referencial consistency but not the serialization. To evade a preempt_disable here a local lock would be needed. Therapie: * add local lock: * and re-introduce local serialization: Tested on x86 with high network load using the testcase from Sami Pietikainen while : ; do wget -O - ftp://LOCAL_SERVER/empty_file > /dev/null 2>&1; done Link: http://www.spinics.net/lists/linux-rt-users/msg11007.html Cc: stable-rt@vger.kernel.org Signed-off-by: Nicholas Mc Guire <der.herr@hofr.at> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
2014-05-14net: Use get_cpu_light() in ip_send_unicast_reply()Thomas Gleixner
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14net: Another local_irq_disable/kmalloc headacheThomas Gleixner
Replace it by a local lock. Though that's pretty inefficient :( Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14net,RT:REmove preemption disabling in netif_rx()Priyanka Jain
1)enqueue_to_backlog() (called from netif_rx) should be bind to a particluar CPU. This can be achieved by disabling migration. No need to disable preemption 2)Fixes crash "BUG: scheduling while atomic: ksoftirqd" in case of RT. If preemption is disabled, enqueue_to_backog() is called in atomic context. And if backlog exceeds its count, kfree_skb() is called. But in RT, kfree_skb() might gets scheduled out, so it expects non atomic context. 3)When CONFIG_PREEMPT_RT_FULL is not defined, migrate_enable(), migrate_disable() maps to preempt_enable() and preempt_disable(), so no change in functionality in case of non-RT. -Replace preempt_enable(), preempt_disable() with migrate_enable(), migrate_disable() respectively -Replace get_cpu(), put_cpu() with get_cpu_light(), put_cpu_light() respectively Signed-off-by: Priyanka Jain <Priyanka.Jain@freescale.com> Acked-by: Rajan Srivastava <Rajan.Srivastava@freescale.com> Cc: <rostedt@goodmis.orgn> Link: http://lkml.kernel.org/r/1337227511-2271-1-git-send-email-Priyanka.Jain@freescale.com Cc: stable-rt@vger.kernel.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14scsi: qla2xxx: Use local_irq_save_nort() in qla2x00_pollJohn Kacur
RT triggers the following: [ 11.307652] [<ffffffff81077b27>] __might_sleep+0xe7/0x110 [ 11.307663] [<ffffffff8150e524>] rt_spin_lock+0x24/0x60 [ 11.307670] [<ffffffff8150da78>] ? rt_spin_lock_slowunlock+0x78/0x90 [ 11.307703] [<ffffffffa0272d83>] qla24xx_intr_handler+0x63/0x2d0 [qla2xxx] [ 11.307736] [<ffffffffa0262307>] qla2x00_poll+0x67/0x90 [qla2xxx] Function qla2x00_poll does local_irq_save() before calling qla24xx_intr_handler which has a spinlock. Since spinlocks are sleepable on rt, it is not allowed to call them with interrupts disabled. Therefore we use local_irq_save_nort() instead which saves flags without disabling interrupts. This fix needs to be applied to v3.0-rt, v3.2-rt and v3.4-rt Suggested-by: Thomas Gleixner Signed-off-by: John Kacur <jkacur@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: David Sommerseth <davids@redhat.com> Link: http://lkml.kernel.org/r/1335523726-10024-1-git-send-email-jkacur@redhat.com Cc: stable-rt@vger.kernel.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14cpu_down: move migrate_enable() backTiejun Chen
Commit 08c1ab68, "hotplug-use-migrate-disable.patch", intends to use migrate_enable()/migrate_disable() to replace that combination of preempt_enable() and preempt_disable(), but actually in !CONFIG_PREEMPT_RT_FULL case, migrate_enable()/migrate_disable() are still equal to preempt_enable()/preempt_disable(). So that followed cpu_hotplug_begin()/cpu_unplug_begin(cpu) would go schedule() to trigger schedule_debug() like this: _cpu_down() | + migrate_disable() = preempt_disable() | + cpu_hotplug_begin() or cpu_unplug_begin() | + schedule() | + __schedule() | + preempt_disable(); | + __schedule_bug() is true! So we should move migrate_enable() as the original scheme. Cc: stable-rt@vger.kernel.org Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
2014-05-14kernel/hotplug: restore original cpu mask oncpu/downSebastian Andrzej Siewior
If a task which is allowed to run only on CPU X puts CPU Y down then it will be allowed on all CPUs but the on CPU Y after it comes back from kernel. This patch ensures that we don't lose the initial setting unless the CPU the task is running is going down. Cc: stable-rt@vger.kernel.org Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
2014-05-14kernel/cpu: fix cpu down problem if kthread's cpu is going downSebastian Andrzej Siewior
If kthread is pinned to CPUx and CPUx is going down then we get into trouble: - first the unplug thread is created - it will set itself to hp->unplug. As a result, every task that is going to take a lock, has to leave the CPU. - the CPU_DOWN_PREPARE notifier are started. The worker thread will start a new process for the "high priority worker". Now kthread would like to take a lock but since it can't leave the CPU it will never complete its task. We could fire the unplug thread after the notifier but then the cpu is no longer marked "online" and the unplug thread will run on CPU0 which was fixed before :) So instead the unplug thread is started and kept waiting until the notfier complete their work. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
2014-05-14cpu hotplug: Document why PREEMPT_RT uses a spinlockSteven Rostedt
The patch: cpu: Make hotplug.lock a "sleeping" spinlock on RT Tasks can block on hotplug.lock in pin_current_cpu(), but their state might be != RUNNING. So the mutex wakeup will set the state unconditionally to RUNNING. That might cause spurious unexpected wakeups. We could provide a state preserving mutex_lock() function, but this is semantically backwards. So instead we convert the hotplug.lock() to a spinlock for RT, which has the state preserving semantics already. Fixed a bug where the hotplug lock on PREEMPT_RT can be called after a task set its state to TASK_UNINTERRUPTIBLE and before it called schedule. If the hotplug_lock used a mutex, and there was contention, the current task's state would be turned to TASK_RUNNABLE and the schedule call will not sleep. This caused unexpected results. Although the patch had a description of the change, the code had no comments about it. This causes confusion to those that review the code, and as PREEMPT_RT is held in a quilt queue and not git, it's not as easy to see why a change was made. Even if it was in git, the code should still have a comment for something as subtle as this. Document the rational for using a spinlock on PREEMPT_RT in the hotplug lock code. Reported-by: Nicholas Mc Guire <der.herr@hofr.at> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
2014-05-14cpu/rt: Rework cpu down for PREEMPT_RTSteven Rostedt
Bringing a CPU down is a pain with the PREEMPT_RT kernel because tasks can be preempted in many more places than in non-RT. In order to handle per_cpu variables, tasks may be pinned to a CPU for a while, and even sleep. But these tasks need to be off the CPU if that CPU is going down. Several synchronization methods have been tried, but when stressed they failed. This is a new approach. A sync_tsk thread is still created and tasks may still block on a lock when the CPU is going down, but how that works is a bit different. When cpu_down() starts, it will create the sync_tsk and wait on it to inform that current tasks that are pinned on the CPU are no longer pinned. But new tasks that are about to be pinned will still be allowed to do so at this time. Then the notifiers are called. Several notifiers will bring down tasks that will enter these locations. Some of these tasks will take locks of other tasks that are on the CPU. If we don't let those other tasks continue, but make them block until CPU down is done, the tasks that the notifiers are waiting on will never complete as they are waiting for the locks held by the tasks that are blocked. Thus we still let the task pin the CPU until the notifiers are done. After the notifiers run, we then make new tasks entering the pinned CPU sections grab a mutex and wait. This mutex is now a per CPU mutex in the hotplug_pcp descriptor. To help things along, a new function in the scheduler code is created called migrate_me(). This function will try to migrate the current task off the CPU this is going down if possible. When the sync_tsk is created, all tasks will then try to migrate off the CPU going down. There are several cases that this wont work, but it helps in most cases. After the notifiers are called and if a task can't migrate off but enters the pin CPU sections, it will be forced to wait on the hotplug_pcp mutex until the CPU down is complete. Then the scheduler will force the migration anyway. Also, I found that THREAD_BOUND need to also be accounted for in the pinned CPU, and the migrate_disable no longer treats them special. This helps fix issues with ksoftirqd and workqueue that unbind on CPU down. Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14cpu: Make hotplug.lock a "sleeping" spinlock on RTSteven Rostedt
Tasks can block on hotplug.lock in pin_current_cpu(), but their state might be != RUNNING. So the mutex wakeup will set the state unconditionally to RUNNING. That might cause spurious unexpected wakeups. We could provide a state preserving mutex_lock() function, but this is semantically backwards. So instead we convert the hotplug.lock() to a spinlock for RT, which has the state preserving semantics already. Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Cc: Carsten Emde <C.Emde@osadl.org> Cc: John Kacur <jkacur@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Clark Williams <clark.williams@gmail.com> Cc: stable-rt@vger.kernel.org Link: http://lkml.kernel.org/r/1330702617.25686.265.camel@gandalf.stny.rr.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14seqlock: consolidate spin_lock/unlock waiting with spin_unlock_waitNicholas Mc Guire
since c2f21ce ("locking: Implement new raw_spinlock") include/linux/spinlock.h includes spin_unlock_wait() to wait for a concurren holder of a lock. this patch just moves over to that API. spin_unlock_wait covers both raw_spinlock_t and spinlock_t so it should be safe here as well. the added rt-variant of read_seqbegin in include/linux/seqlock.h that is being modified, was introduced by patch: seqlock-prevent-rt-starvation.patch behavior should be unchanged. Signed-off-by: Nicholas Mc Guire <der.herr@hofr.at> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
2014-05-14seqlock: Prevent rt starvationThomas Gleixner
If a low prio writer gets preempted while holding the seqlock write locked, a high prio reader spins forever on RT. To prevent this let the reader grab the spinlock, so it blocks and eventually boosts the writer. This way the writer can proceed and endless spinning is prevented. For seqcount writers we disable preemption over the update code path. Thaanks to Al Viro for distangling some VFS code to make that possible. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable-rt@vger.kernel.org
2014-05-14random: Make it work on rtThomas Gleixner
Delegate the random insertion to the forced threaded interrupt handler. Store the return IP of the hard interrupt handler in the irq descriptor and feed it into the random generator as a source of entropy. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: stable-rt@vger.kernel.org
2014-05-14cpumask: Disable CONFIG_CPUMASK_OFFSTACK for RTThomas Gleixner
We can't deal with the cpumask allocations which happen in atomic context (see arch/x86/kernel/apic/io_apic.c) on RT right now. Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14acpi/rt: Convert acpi_gbl_hardware lock back to a raw_spinlock_tSteven Rostedt
We hit the following bug with 3.6-rt: [ 5.898990] BUG: scheduling while atomic: swapper/3/0/0x00000002 [ 5.898991] no locks held by swapper/3/0. [ 5.898993] Modules linked in: [ 5.898996] Pid: 0, comm: swapper/3 Not tainted 3.6.11-rt28.19.el6rt.x86_64.debug #1 [ 5.898997] Call Trace: [ 5.899011] [<ffffffff810804e7>] __schedule_bug+0x67/0x90 [ 5.899028] [<ffffffff81577923>] __schedule+0x793/0x7a0 [ 5.899032] [<ffffffff810b4e40>] ? debug_rt_mutex_print_deadlock+0x50/0x200 [ 5.899034] [<ffffffff81577b89>] schedule+0x29/0x70 [ 5.899036] BUG: scheduling while atomic: swapper/7/0/0x00000002 [ 5.899037] no locks held by swapper/7/0. [ 5.899039] [<ffffffff81578525>] rt_spin_lock_slowlock+0xe5/0x2f0 [ 5.899040] Modules linked in: [ 5.899041] [ 5.899045] [<ffffffff81579a58>] ? _raw_spin_unlock_irqrestore+0x38/0x90 [ 5.899046] Pid: 0, comm: swapper/7 Not tainted 3.6.11-rt28.19.el6rt.x86_64.debug #1 [ 5.899047] Call Trace: [ 5.899049] [<ffffffff81578bc6>] rt_spin_lock+0x16/0x40 [ 5.899052] [<ffffffff810804e7>] __schedule_bug+0x67/0x90 [ 5.899054] [<ffffffff8157d3f0>] ? notifier_call_chain+0x80/0x80 [ 5.899056] [<ffffffff81577923>] __schedule+0x793/0x7a0 [ 5.899059] [<ffffffff812f2034>] acpi_os_acquire_lock+0x1f/0x23 [ 5.899062] [<ffffffff810b4e40>] ? debug_rt_mutex_print_deadlock+0x50/0x200 [ 5.899068] [<ffffffff8130be64>] acpi_write_bit_register+0x33/0xb0 [ 5.899071] [<ffffffff81577b89>] schedule+0x29/0x70 [ 5.899072] [<ffffffff8130be13>] ? acpi_read_bit_register+0x33/0x51 [ 5.899074] [<ffffffff81578525>] rt_spin_lock_slowlock+0xe5/0x2f0 [ 5.899077] [<ffffffff8131d1fc>] acpi_idle_enter_bm+0x8a/0x28e [ 5.899079] [<ffffffff81579a58>] ? _raw_spin_unlock_irqrestore+0x38/0x90 [ 5.899081] [<ffffffff8107e5da>] ? this_cpu_load+0x1a/0x30 [ 5.899083] [<ffffffff81578bc6>] rt_spin_lock+0x16/0x40 [ 5.899087] [<ffffffff8144c759>] cpuidle_enter+0x19/0x20 [ 5.899088] [<ffffffff8157d3f0>] ? notifier_call_chain+0x80/0x80 [ 5.899090] [<ffffffff8144c777>] cpuidle_enter_state+0x17/0x50 [ 5.899092] [<ffffffff812f2034>] acpi_os_acquire_lock+0x1f/0x23 [ 5.899094] [<ffffffff8144d1a1>] cpuidle899101] [<ffffffff8130be13>] ? As the acpi code disables interrupts in acpi_idle_enter_bm, and calls code that grabs the acpi lock, it causes issues as the lock is currently in RT a sleeping lock. The lock was converted from a raw to a sleeping lock due to some previous issues, and tests that showed it didn't seem to matter. Unfortunately, it did matter for one of our boxes. This patch converts the lock back to a raw lock. I've run this code on a few of my own machines, one being my laptop that uses the acpi quite extensively. I've been able to suspend and resume without issues. [ tglx: Made the change exclusive for acpi_gbl_hardware_lock ] Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Cc: John Kacur <jkacur@gmail.com> Cc: Clark Williams <clark@redhat.com> Link: http://lkml.kernel.org/r/1360765565.23152.5.camel@gandalf.local.home Cc: stable-rt@vger.kernel.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
2014-05-14dm: Make rt awareThomas Gleixner
Use the BUG_ON_NORT variant for the irq_disabled() checks. RT has interrupts legitimately enabled here as we cant deadlock against the irq thread due to the "sleeping spinlocks" conversion. Reported-by: Luis Claudio R. Goncalves <lclaudio@uudg.org> Cc: stable-rt@vger.kernel.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14crypto: Reduce preempt disabled regions, more algosSebastian Andrzej Siewior
Don Estabrook reported | kernel: WARNING: CPU: 2 PID: 858 at kernel/sched/core.c:2428 migrate_disable+0xed/0x100() | kernel: WARNING: CPU: 2 PID: 858 at kernel/sched/core.c:2462 migrate_enable+0x17b/0x200() | kernel: WARNING: CPU: 3 PID: 865 at kernel/sched/core.c:2428 migrate_disable+0xed/0x100() and his backtrace showed some crypto functions which looked fine. The problem is the following sequence: glue_xts_crypt_128bit() { blkcipher_walk_virt(); /* normal migrate_disable() */ glue_fpu_begin(); /* get atomic */ while (nbytes) { __glue_xts_crypt_128bit(); blkcipher_walk_done(); /* with nbytes = 0, migrate_enable() * while we are atomic */ }; glue_fpu_end() /* no longer atomic */ } and this is why the counter get out of sync and the warning is printed. The other problem is that we are non-preemptible between glue_fpu_begin() and glue_fpu_end() and the latency grows. To fix this, I shorten the FPU off region and ensure blkcipher_walk_done() is called with preemption enabled. This might hurt the performance because we now enable/disable the FPU state more often but we gain lower latency and the bug is gone. Cc: stable-rt@vger.kernel.org Reported-by: Don Estabrook <don.estabrook@gmail.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
2014-05-14x86: crypto: Reduce preempt disabled regionsPeter Zijlstra
Restrict the preempt disabled regions to the actual floating point operations and enable preemption for the administrative actions. This is necessary on RT to avoid that kfree and other operations are called with preemption disabled. Reported-and-tested-by: Carsten Emde <cbe@osadl.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: stable-rt@vger.kernel.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14scsi-fcoe-rt-aware.patchThomas Gleixner
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14x86-kvm-require-const-tsc-for-rt.patchThomas Gleixner
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14ipc/sem: Rework semaphore wakeupsPeter Zijlstra
Current sysv sems have a weird ass wakeup scheme that involves keeping preemption disabled over a potential O(n^2) loop and busy waiting on that on other CPUs. Kill this and simply wake the task directly from under the sem_lock. This was discovered by a migrate_disable() debug feature that disallows: spin_lock(); preempt_disable(); spin_unlock() preempt_enable(); Cc: Manfred Spraul <manfred@colorfullife.com> Suggested-by: Thomas Gleixner <tglx@linutronix.de> Reported-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Manfred Spraul <manfred@colorfullife.com> Link: http://lkml.kernel.org/r/1315994224.5040.1.camel@twins Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14arm-enable-highmem-for-rt.patchThomas Gleixner
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14arm/highmem: flush tlb on unmapSebastian Andrzej Siewior
The tlb should be flushed on unmap and thus make the mapping entry invalid. This is only done in the non-debug case which does not look right. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
2014-05-14x86/highmem: add a "already used pte" checkSebastian Andrzej Siewior
This is a copy from kmap_atomic_prot(). Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
2014-05-14mm, rt: kmap_atomic schedulingPeter Zijlstra
In fact, with migrate_disable() existing one could play games with kmap_atomic. You could save/restore the kmap_atomic slots on context switch (if there are any in use of course), this should be esp easy now that we have a kmap_atomic stack. Something like the below.. it wants replacing all the preempt_disable() stuff with pagefault_disable() && migrate_disable() of course, but then you can flip kmaps around like below. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> [dvhart@linux.intel.com: build fix] Link: http://lkml.kernel.org/r/1311842631.5890.208.camel@twins [tglx@linutronix.de: Get rid of the per cpu variable and store the idx and the pte content right away in the task struct. Shortens the context switch code. ]
2014-05-14add /sys/kernel/realtime entryClark Williams
Add a /sys/kernel entry to indicate that the kernel is a realtime kernel. Clark says that he needs this for udev rules, udev needs to evaluate if its a PREEMPT_RT kernel a few thousand times and parsing uname output is too slow or so. Are there better solutions? Should it exist and return 0 on !-rt? Signed-off-by: Clark Williams <williams@redhat.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
2014-05-14kgdb/serial: Short term workaroundJason Wessel
On 07/27/2011 04:37 PM, Thomas Gleixner wrote: > - KGDB (not yet disabled) is reportedly unusable on -rt right now due > to missing hacks in the console locking which I dropped on purpose. > To work around this in the short term you can use this patch, in addition to the clocksource watchdog patch that Thomas brewed up. Comments are welcome of course. Ultimately the right solution is to change separation between the console and the HW to have a polled mode + work queue so as not to introduce any kind of latency. Thanks, Jason.
2014-05-14net: sysrq via icmpCarsten Emde
There are (probably rare) situations when a system crashed and the system console becomes unresponsive but the network icmp layer still is alive. Wouldn't it be wonderful, if we then could submit a sysreq command via ping? This patch provides this facility. Please consult the updated documentation Documentation/sysrq.txt for details. Signed-off-by: Carsten Emde <C.Emde@osadl.org>
2014-05-14net: Avoid livelock in net_tx_action() on RTSteven Rostedt
qdisc_lock is taken w/o disabling interrupts or bottom halfs. So code holding a qdisc_lock() can be interrupted and softirqs can run on the return of interrupt in !RT. The spin_trylock() in net_tx_action() makes sure, that the softirq does not deadlock. When the lock can't be acquired q is requeued and the NET_TX softirq is raised. That causes the softirq to run over and over. That works in mainline as do_softirq() has a retry loop limit and leaves the softirq processing in the interrupt return path and schedules ksoftirqd. The task which holds qdisc_lock cannot be preempted, so the lock is released and either ksoftirqd or the next softirq in the return from interrupt path can proceed. Though it's a bit strange to actually run MAX_SOFTIRQ_RESTART (10) loops before it decides to bail out even if it's clear in the first iteration :) On RT all softirq processing is done in a FIFO thread and we don't have a loop limit, so ksoftirqd preempts the lock holder forever and unqueues and requeues until the reset button is hit. Due to the forced threading of ksoftirqd on RT we actually cannot deadlock on qdisc_lock because it's a "sleeping lock". So it's safe to replace the spin_trylock() with a spin_lock(). When contended, ksoftirqd is scheduled out and the lock holder can proceed. [ tglx: Massaged changelog and code comments ] Solved-by: Thomas Gleixner <tglx@linuxtronix.de> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Tested-by: Carsten Emde <cbe@osadl.org> Cc: Clark Williams <williams@redhat.com> Cc: John Kacur <jkacur@redhat.com> Cc: Luis Claudio R. Goncalves <lclaudio@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14mips-disable-highmem-on-rt.patchThomas Gleixner
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14arm/unwind: use a raw_spin_lockSebastian Andrzej Siewior
Mostly unwind is done with irqs enabled however SLUB may call it with irqs disabled while creating a new SLUB cache. I had system freeze while loading a module which called kmem_cache_create() on init. That means SLUB's __slab_alloc() disabled interrupts and then ->new_slab_objects() ->new_slab() ->setup_object() ->setup_object_debug() ->init_tracking() ->set_track() ->save_stack_trace() ->save_stack_trace_tsk() ->walk_stackframe() ->unwind_frame() ->unwind_find_idx() =>spin_lock_irqsave(&unwind_lock); Cc: stable-rt@vger.kernel.org Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
2014-05-14ARM: at91: tclib: Default to tclib timer for RTThomas Gleixner
RT is not too happy about the shared timer interrupt in AT91 devices. Default to tclib timer for RT. Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14arm-disable-highmem-on-rt.patchThomas Gleixner
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
2014-05-14power-disable-highmem-on-rt.patchThomas Gleixner
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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