litmus-rt.git, branch wip-master-2.6.33-rt The LITMUS^RT kernel. Avoid deadlock when switching task policy to BACKGROUND (ugly) 2010-06-10T17:24:54+00:00 Andrea Bastoni bastoni@cs.unc.edu 2010-06-10T17:24:54+00:00 53d9688562a712a9b3e0265b51f2e60fec103799 When (re)setting Litmus task policy to BACKGROUND, kfree is called while in atomic context. This cannot be done in PreemptRT as it will deadlock (this commit fixes the below trace). Properly freeing rt-task structures while not holding proper locks breaks various assumptions in the code and therefore these operations cannot be easily postponed (to a moment when we don't hold the locks). The solution is a bad hack and if the policy is reset to BACKGROUND task we leak some memory. Better solutions are very welcomed. [ 52.850018] ======================================================= [ 52.850018] [ INFO: possible circular locking dependency detected ] [ 52.850018] 2.6.33.5-rt22-litmus2010 #441 [ 52.850018] ------------------------------------------------------- [ 52.850018] longtest_g/1637 is trying to acquire lock: [ 52.850018] (per_cpu__lock_slab_locked){......}, at: [<ffffffff8142b783>] rt_spin_lock_slowlock+0x33/0x360 [ 52.850018] [ 52.850018] but task is already holding lock: [ 52.850018] (&rq->lock){-...-.}, at: [<ffffffff8102ee52>] __sched_setscheduler+0x112/0x4f0 [ 52.850018] [ 52.850018] which lock already depends on the new lock. [ 52.850018] [ 52.850018] [ 52.850018] the existing dependency chain (in reverse order) is: [ 52.850018] [ 52.850018] -> #2 (&rq->lock){-...-.}: [ 52.850018] [<ffffffff81060954>] __lock_acquire+0x13c4/0x1cd0 [ 52.850018] [<ffffffff810612bc>] lock_acquire+0x5c/0x80 [ 52.850018] [<ffffffff8142cc76>] _raw_spin_lock+0x36/0x50 [ 52.850018] [<ffffffff8102551e>] task_rq_lock+0x5e/0xb0 [ 52.850018] [<ffffffff8102fa44>] try_to_wake_up+0x64/0x420 [ 52.850018] [<ffffffff8102fe65>] wake_up_process_mutex+0x15/0x20 [ 52.850018] [<ffffffff8106708e>] wakeup_next_waiter+0x9e/0x1b0 [ 52.850018] [<ffffffff8142b70f>] rt_spin_lock_slowunlock+0x4f/0x90 [ 52.850018] [<ffffffff8142c419>] rt_spin_unlock+0x49/0x50 [ 52.850018] [<ffffffff8102ceb4>] complete+0x44/0x50 [ 52.850018] [<ffffffff8104d07c>] kthread+0x7c/0xc0 [ 52.850018] [<ffffffff81003214>] kernel_thread_helper+0x4/0x10 [ 52.850018] [ 52.850018] -> #1 (&p->pi_lock){......}: [ 52.850018] [<ffffffff81060954>] __lock_acquire+0x13c4/0x1cd0 [ 52.850018] [<ffffffff810612bc>] lock_acquire+0x5c/0x80 [ 52.850018] [<ffffffff8142cc76>] _raw_spin_lock+0x36/0x50 [ 52.850018] [<ffffffff81066859>] task_blocks_on_rt_mutex+0x39/0x210 [ 52.850018] [<ffffffff8142b9c3>] rt_spin_lock_slowlock+0x273/0x360 [ 52.850018] [<ffffffff8142c383>] rt_spin_lock+0x43/0x90 [ 52.850018] [<ffffffff810ab23e>] _slab_irq_disable+0x4e/0x70 [ 52.850018] [<ffffffff810ab93f>] kmem_cache_free+0x1f/0xf0 [ 52.850018] [<ffffffff810b34a1>] file_free_rcu+0x31/0x40 [ 52.850018] [<ffffffff81074a48>] __rcu_process_callbacks+0x128/0x3a0 [ 52.850018] [<ffffffff81074d3b>] rcu_process_callbacks+0x7b/0x90 [ 52.850018] [<ffffffff8103a96f>] run_ksoftirqd+0x14f/0x310 [ 52.850018] [<ffffffff8104d0a6>] kthread+0xa6/0xc0 [ 52.850018] [<ffffffff81003214>] kernel_thread_helper+0x4/0x10 [ 52.850018] [ 52.850018] -> #0 (per_cpu__lock_slab_locked){......}: [ 52.850018] [<ffffffff8106120c>] __lock_acquire+0x1c7c/0x1cd0 [ 52.850018] [<ffffffff810612bc>] lock_acquire+0x5c/0x80 [ 52.850018] [<ffffffff8142cd91>] _raw_spin_lock_irqsave+0x41/0x60 [ 52.850018] [<ffffffff8142b783>] rt_spin_lock_slowlock+0x33/0x360 [ 52.850018] [<ffffffff8142c383>] rt_spin_lock+0x43/0x90 [ 52.850018] [<ffffffff810ab23e>] _slab_irq_disable+0x4e/0x70 [ 52.850018] [<ffffffff810ab93f>] kmem_cache_free+0x1f/0xf0 [ 52.850018] [<ffffffff811d1374>] litmus_exit_task+0x84/0x130 [ 52.850018] [<ffffffff8102f11f>] __sched_setscheduler+0x3df/0x4f0 [ 52.850018] [<ffffffff8102f24e>] sched_setscheduler+0xe/0x10 [ 52.850018] [<ffffffff8102f30d>] do_sched_setscheduler+0xbd/0x100 [ 52.850018] [<ffffffff8102f384>] sys_sched_setscheduler+0x14/0x20 [ 52.850018] [<ffffffff8100246b>] system_call_fastpath+0x16/0x1b [ 52.850018] [ 52.850018] other info that might help us debug this: [ 52.850018] [ 52.850018] 3 locks held by longtest_g/1637: [ 52.850018] #0: (rcu_read_lock){.+.+..}, at: [<ffffffff8102f2bf>] do_sched_setscheduler+0x6f/0x100 [ 52.850018] #1: (&p->pi_lock){......}, at: [<ffffffff8102ee0e>] __sched_setscheduler+0xce/0x4f0 [ 52.850018] #2: (&rq->lock){-...-.}, at: [<ffffffff8102ee52>] __sched_setscheduler+0x112/0x4f0 [ 52.850018] [ 52.850018] stack backtrace: [ 52.850018] Pid: 1637, comm: longtest_g Tainted: G W 2.6.33.5-rt22-litmus2010 #441 [ 52.850018] Call Trace: [ 52.850018] [<ffffffff8105ef10>] print_circular_bug+0x100/0x110 [ 52.850018] [<ffffffff8106120c>] __lock_acquire+0x1c7c/0x1cd0 [ 52.850018] [<ffffffff81429659>] ? printk+0x67/0x69 [ 52.850018] [<ffffffff8100246b>] ? system_call_fastpath+0x16/0x1b [ 52.850018] [<ffffffff8100246b>] ? system_call_fastpath+0x16/0x1b [ 52.850018] [<ffffffff810612bc>] lock_acquire+0x5c/0x80 [ 52.850018] [<ffffffff8142b783>] ? rt_spin_lock_slowlock+0x33/0x360 [ 52.850018] [<ffffffff8142cd91>] _raw_spin_lock_irqsave+0x41/0x60 [ 52.850018] [<ffffffff8142b783>] ? rt_spin_lock_slowlock+0x33/0x360 [ 52.850018] [<ffffffff81005649>] ? dump_trace+0x129/0x330 [ 52.850018] [<ffffffff8142b783>] rt_spin_lock_slowlock+0x33/0x360 [ 52.850018] [<ffffffff8142c383>] rt_spin_lock+0x43/0x90 [ 52.850018] [<ffffffff810ab23e>] _slab_irq_disable+0x4e/0x70 [ 52.850018] [<ffffffff810ab93f>] kmem_cache_free+0x1f/0xf0 [ 52.850018] [<ffffffff811d1374>] litmus_exit_task+0x84/0x130 [ 52.850018] [<ffffffff810242d8>] ? dequeue_task+0x48/0x90 [ 52.850018] [<ffffffff8102f11f>] __sched_setscheduler+0x3df/0x4f0 [ 52.850018] [<ffffffff8102f24e>] sched_setscheduler+0xe/0x10 [ 52.850018] [<ffffffff8102f30d>] do_sched_setscheduler+0xbd/0x100 [ 52.850018] [<ffffffff8102f2bf>] ? do_sched_setscheduler+0x6f/0x100 [ 52.850018] [<ffffffff8142bf02>] ? trace_hardirqs_on_thunk+0x3a/0x3f [ 52.850018] [<ffffffff8102f384>] sys_sched_setscheduler+0x14/0x20 [ 52.850018] [<ffffffff8100246b>] system_call_fastpath+0x16/0x1b 
When (re)setting Litmus task policy to BACKGROUND, kfree is called while
in atomic context. This cannot be done in PreemptRT as it will deadlock
(this commit fixes the below trace).

Properly freeing rt-task structures while not holding proper locks
breaks various assumptions in the code and therefore these operations
cannot be easily postponed (to a moment when we don't hold the locks).
The solution is a bad hack and if the policy is reset to BACKGROUND task
we leak some memory.
Better solutions are very welcomed.

[   52.850018] =======================================================
[   52.850018] [ INFO: possible circular locking dependency detected ]
[   52.850018] 2.6.33.5-rt22-litmus2010 #441
[   52.850018] -------------------------------------------------------
[   52.850018] longtest_g/1637 is trying to acquire lock:
[   52.850018]  (per_cpu__lock_slab_locked){......}, at: [<ffffffff8142b783>] rt_spin_lock_slowlock+0x33/0x360
[   52.850018]
[   52.850018] but task is already holding lock:
[   52.850018]  (&rq->lock){-...-.}, at: [<ffffffff8102ee52>] __sched_setscheduler+0x112/0x4f0
[   52.850018]
[   52.850018] which lock already depends on the new lock.
[   52.850018]
[   52.850018]
[   52.850018] the existing dependency chain (in reverse order) is:
[   52.850018]
[   52.850018] -> #2 (&rq->lock){-...-.}:
[   52.850018]        [<ffffffff81060954>] __lock_acquire+0x13c4/0x1cd0
[   52.850018]        [<ffffffff810612bc>] lock_acquire+0x5c/0x80
[   52.850018]        [<ffffffff8142cc76>] _raw_spin_lock+0x36/0x50
[   52.850018]        [<ffffffff8102551e>] task_rq_lock+0x5e/0xb0
[   52.850018]        [<ffffffff8102fa44>] try_to_wake_up+0x64/0x420
[   52.850018]        [<ffffffff8102fe65>] wake_up_process_mutex+0x15/0x20
[   52.850018]        [<ffffffff8106708e>] wakeup_next_waiter+0x9e/0x1b0
[   52.850018]        [<ffffffff8142b70f>] rt_spin_lock_slowunlock+0x4f/0x90
[   52.850018]        [<ffffffff8142c419>] rt_spin_unlock+0x49/0x50
[   52.850018]        [<ffffffff8102ceb4>] complete+0x44/0x50
[   52.850018]        [<ffffffff8104d07c>] kthread+0x7c/0xc0
[   52.850018]        [<ffffffff81003214>] kernel_thread_helper+0x4/0x10
[   52.850018]
[   52.850018] -> #1 (&p->pi_lock){......}:
[   52.850018]        [<ffffffff81060954>] __lock_acquire+0x13c4/0x1cd0
[   52.850018]        [<ffffffff810612bc>] lock_acquire+0x5c/0x80
[   52.850018]        [<ffffffff8142cc76>] _raw_spin_lock+0x36/0x50
[   52.850018]        [<ffffffff81066859>] task_blocks_on_rt_mutex+0x39/0x210
[   52.850018]        [<ffffffff8142b9c3>] rt_spin_lock_slowlock+0x273/0x360
[   52.850018]        [<ffffffff8142c383>] rt_spin_lock+0x43/0x90
[   52.850018]        [<ffffffff810ab23e>] _slab_irq_disable+0x4e/0x70
[   52.850018]        [<ffffffff810ab93f>] kmem_cache_free+0x1f/0xf0
[   52.850018]        [<ffffffff810b34a1>] file_free_rcu+0x31/0x40
[   52.850018]        [<ffffffff81074a48>] __rcu_process_callbacks+0x128/0x3a0
[   52.850018]        [<ffffffff81074d3b>] rcu_process_callbacks+0x7b/0x90
[   52.850018]        [<ffffffff8103a96f>] run_ksoftirqd+0x14f/0x310
[   52.850018]        [<ffffffff8104d0a6>] kthread+0xa6/0xc0
[   52.850018]        [<ffffffff81003214>] kernel_thread_helper+0x4/0x10
[   52.850018]
[   52.850018] -> #0 (per_cpu__lock_slab_locked){......}:
[   52.850018]        [<ffffffff8106120c>] __lock_acquire+0x1c7c/0x1cd0
[   52.850018]        [<ffffffff810612bc>] lock_acquire+0x5c/0x80
[   52.850018]        [<ffffffff8142cd91>] _raw_spin_lock_irqsave+0x41/0x60
[   52.850018]        [<ffffffff8142b783>] rt_spin_lock_slowlock+0x33/0x360
[   52.850018]        [<ffffffff8142c383>] rt_spin_lock+0x43/0x90
[   52.850018]        [<ffffffff810ab23e>] _slab_irq_disable+0x4e/0x70
[   52.850018]        [<ffffffff810ab93f>] kmem_cache_free+0x1f/0xf0
[   52.850018]        [<ffffffff811d1374>] litmus_exit_task+0x84/0x130
[   52.850018]        [<ffffffff8102f11f>] __sched_setscheduler+0x3df/0x4f0
[   52.850018]        [<ffffffff8102f24e>] sched_setscheduler+0xe/0x10
[   52.850018]        [<ffffffff8102f30d>] do_sched_setscheduler+0xbd/0x100
[   52.850018]        [<ffffffff8102f384>] sys_sched_setscheduler+0x14/0x20
[   52.850018]        [<ffffffff8100246b>] system_call_fastpath+0x16/0x1b
[   52.850018]
[   52.850018] other info that might help us debug this:
[   52.850018]
[   52.850018] 3 locks held by longtest_g/1637:
[   52.850018]  #0:  (rcu_read_lock){.+.+..}, at: [<ffffffff8102f2bf>] do_sched_setscheduler+0x6f/0x100
[   52.850018]  #1:  (&p->pi_lock){......}, at: [<ffffffff8102ee0e>] __sched_setscheduler+0xce/0x4f0
[   52.850018]  #2:  (&rq->lock){-...-.}, at: [<ffffffff8102ee52>] __sched_setscheduler+0x112/0x4f0
[   52.850018]
[   52.850018] stack backtrace:
[   52.850018] Pid: 1637, comm: longtest_g Tainted: G        W 2.6.33.5-rt22-litmus2010 #441
[   52.850018] Call Trace:
[   52.850018]  [<ffffffff8105ef10>] print_circular_bug+0x100/0x110
[   52.850018]  [<ffffffff8106120c>] __lock_acquire+0x1c7c/0x1cd0
[   52.850018]  [<ffffffff81429659>] ? printk+0x67/0x69
[   52.850018]  [<ffffffff8100246b>] ? system_call_fastpath+0x16/0x1b
[   52.850018]  [<ffffffff8100246b>] ? system_call_fastpath+0x16/0x1b
[   52.850018]  [<ffffffff810612bc>] lock_acquire+0x5c/0x80
[   52.850018]  [<ffffffff8142b783>] ? rt_spin_lock_slowlock+0x33/0x360
[   52.850018]  [<ffffffff8142cd91>] _raw_spin_lock_irqsave+0x41/0x60
[   52.850018]  [<ffffffff8142b783>] ? rt_spin_lock_slowlock+0x33/0x360
[   52.850018]  [<ffffffff81005649>] ? dump_trace+0x129/0x330
[   52.850018]  [<ffffffff8142b783>] rt_spin_lock_slowlock+0x33/0x360
[   52.850018]  [<ffffffff8142c383>] rt_spin_lock+0x43/0x90
[   52.850018]  [<ffffffff810ab23e>] _slab_irq_disable+0x4e/0x70
[   52.850018]  [<ffffffff810ab93f>] kmem_cache_free+0x1f/0xf0
[   52.850018]  [<ffffffff811d1374>] litmus_exit_task+0x84/0x130
[   52.850018]  [<ffffffff810242d8>] ? dequeue_task+0x48/0x90
[   52.850018]  [<ffffffff8102f11f>] __sched_setscheduler+0x3df/0x4f0
[   52.850018]  [<ffffffff8102f24e>] sched_setscheduler+0xe/0x10
[   52.850018]  [<ffffffff8102f30d>] do_sched_setscheduler+0xbd/0x100
[   52.850018]  [<ffffffff8102f2bf>] ? do_sched_setscheduler+0x6f/0x100
[   52.850018]  [<ffffffff8142bf02>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[   52.850018]  [<ffffffff8102f384>] sys_sched_setscheduler+0x14/0x20
[   52.850018]  [<ffffffff8100246b>] system_call_fastpath+0x16/0x1b
Use a non-sleeping lock to protect fmlp locking operations 2010-06-10T17:02:23+00:00 Andrea Bastoni bastoni@cs.unc.edu 2010-06-10T17:02:23+00:00 5980b2330359d002e4e2278327ff80307504b848 The wait_queue_t lock used to protect fmlp_down and fmlp_up operations in vanilla kernel is a sleeping lock in PreemptRT. We call fmlp operations from atomic contexts. This commit replaces the wait_queue lock with a raw_spin_lock. 
The wait_queue_t lock used to protect fmlp_down and fmlp_up operations
in vanilla kernel is a sleeping lock in PreemptRT. We call fmlp
operations from atomic contexts. This commit replaces the wait_queue
lock with a raw_spin_lock.
Make platform-specific Feather-Trace depend on !CONFIG_DEBUG_RODATA 2010-06-09T20:57:12+00:00 Bjoern B. Brandenburg bbb@cs.unc.edu 2010-05-31T16:52:35+00:00 b7723f10b088450c82a84275371d48020309e5f7 Feather-Trace rewrites instructions in the kernel's .text segment. This segment may be write-protected if CONFIG_DEBUG_RODATA is selected. In this case, fall back to the default flag-based Feather-Trace implementation. In the future, we could either adopt the ftrace method of rewriting .text addresses using non-.text mappings or we could consider replacing Feather-Trace with ftrace altogether. For now, this patch avoids unexpected runtime errors. 
Feather-Trace rewrites instructions in the kernel's .text segment.
This segment may be write-protected if CONFIG_DEBUG_RODATA is selected.
In this case, fall back to the default flag-based Feather-Trace
implementation. In the future, we could either adopt the ftrace method
of rewriting .text addresses using non-.text mappings or we could
consider replacing Feather-Trace with ftrace altogether.

For now, this patch avoids unexpected runtime errors.
Make PFAIR optional to prevent build and runtime failures. 2010-06-09T20:56:50+00:00 Bjoern B. Brandenburg bbb@cs.unc.edu 2010-05-31T16:15:51+00:00 e677158a7f913bd010909d013b04c98c3834ece5 The PFAIR plugin always implicitly assumed !NO_HZ (the schedule is wrong if NO_HZ is enabled) and does not built if hrtimers are absent: > litmus/built-in.o: In function `pfair_activate_plugin': > sched_pfair.c:(.text+0x7f07): undefined reference to `cpu_stagger_offset' > litmus/built-in.o: In function `init_pfair': > sched_pfair.c:(.init.text+0x487): undefined reference to `cpu_stagger_offset' cpu_stagger_offset() is only available if hrtimers are enabled. This patch makes these dependencies explicit. 
The PFAIR plugin always implicitly assumed !NO_HZ (the schedule
is wrong if NO_HZ is enabled) and does not built if hrtimers are absent:

> litmus/built-in.o: In function `pfair_activate_plugin':
> sched_pfair.c:(.text+0x7f07): undefined reference to `cpu_stagger_offset'
> litmus/built-in.o: In function `init_pfair':
> sched_pfair.c:(.init.text+0x487): undefined reference to `cpu_stagger_offset'

cpu_stagger_offset() is only available if hrtimers are enabled.

This patch makes these dependencies explicit.
Make C-EDF depend on x86 and SYSFS 2010-06-09T20:56:39+00:00 Andrea Bastoni bastoni@cs.unc.edu 2010-05-31T04:54:07+00:00 95388e6e7f1692c08d66a8ca92b7ac776c3c6350 C-EDF depends on intel_cacheinfo.c (for get_shared_cpu_map()) which is only available on x86 architectures. Furthermore, get_shared_cpu_map() is only available if SYSFS filesystem is present. 
C-EDF depends on intel_cacheinfo.c (for get_shared_cpu_map()) which is
only available on x86 architectures. Furthermore, get_shared_cpu_map()
is only available if SYSFS filesystem is present.
Make smp_send_pull_timers() optional. 2010-06-09T20:56:28+00:00 Bjoern B. Brandenburg bbb@cs.unc.edu 2010-05-30T23:50:52+00:00 0fb33c99d964c63f51216db232047924b1d8b489 There is currently no need to implement this in ARM. So let's make it optional instead. 
There is currently no need to implement this in ARM.
So let's make it optional instead.
Make release master support optional 2010-06-09T20:56:19+00:00 Bjoern B. Brandenburg bbb@cs.unc.edu 2010-05-30T23:46:21+00:00 0c527966dd7dd3e377a0cbcb5b25e225f0adb990 Introduces CONFIG_RELEASE_MASTER and makes release master support dependent on the new symbol. This is useful because dedicated interrupt handling only applies to "large" multicore platforms. This will allow us to not implement smp_send_pull_timers() for all platforms. 
Introduces CONFIG_RELEASE_MASTER and makes release
master support dependent on the new symbol. This is
useful because dedicated interrupt handling only applies
to "large" multicore platforms. This will allow us to
not implement smp_send_pull_timers() for all platforms.
Make compilation of C-EDF optional. 2010-06-09T20:56:08+00:00 Bjoern B. Brandenburg bbb@cs.unc.edu 2010-05-30T22:59:30+00:00 a57cd053183702b68fa6a500af4a6770daacfaf9 C-EDF only makes sense on multicore platforms that have shared caches. Make it possible to disable it on other platforms, in particular, on those that do not export get_shared_cpu_map(). 
C-EDF only makes sense on multicore platforms that have shared caches.
Make it possible to disable it on other platforms, in particular,
on those that do not export get_shared_cpu_map().
Make __ARCH_HAS_FEATHER_TRACE a proper CONFIG_ variable. 2010-06-09T20:55:57+00:00 Bjoern B. Brandenburg bbb@cs.unc.edu 2010-05-30T22:41:28+00:00 a9af0235047575d7bfe5922b63c9eb2742a18f43 The idea of the Feather-Trace default implementation is that LITMUS^RT should work without a specialized Feather-Trace implementation present. This was actually broken. Changes litmus/feather_trace.h to only include asm/feather_trace.h if actually promised by the architecture. 
The idea of the Feather-Trace default implementation is that LITMUS^RT should
work without a specialized Feather-Trace implementation present. This was
actually broken.

Changes litmus/feather_trace.h to only include asm/feather_trace.h if actually
promised by the architecture.
Bugfix: re-insert missing TS_PLUGIN_TICK_END tracing point 2010-06-09T20:55:46+00:00 Andrea Bastoni bastoni@cs.unc.edu 2010-05-28T19:45:23+00:00 93ad471f8a5e2ba8d27a29af3589f156f45cc2f1 Insert PLUGIN_TICK_END tracing point in litmus_tick(). It was lost during the porting of 2008.3 to 2010.1. 
Insert PLUGIN_TICK_END tracing point in litmus_tick(). It was lost during
the porting of 2008.3 to 2010.1.