linux-toradex.git, branch toradex_4.19.y-rt

Merge tag 'v4.19.59-rt24' into toradex_4.19.y-rt

2019-08-16T14:40:08+00:00

Linux 4.19.59-rt24

Linux 4.19.59-rt24

2019-07-23T18:57:39+00:00

mm/zswap: Do not disable preemption in zswap_frontswap_store()

2019-07-23T18:57:14+00:00

[ Upstream commit 4e4cf4be79635e67144632d9135286381acbc95a ]

Zswap causes "BUG: scheduling while atomic" by blocking on a rt_spin_lock() with
preemption disabled. The preemption is disabled by get_cpu_var() in
zswap_frontswap_store() to protect the access of the zswap_dstmem percpu variable.

Use get_locked_var() to protect the percpu zswap_dstmem variable, making the
code preemptive.

As get_cpu_ptr() also disables preemption, replace it by this_cpu_ptr() and
remove the counterpart put_cpu_ptr().

Steps to Reproduce:

    1. # grubby --args "zswap.enabled=1" --update-kernel DEFAULT
    2. # reboot
    3. Calculate the amount o memory to be used by the test:
       ---> grep MemAvailable /proc/meminfo
       ---> Add 25% ~ 50% to that value
    4. # stress --vm 1 --vm-bytes ${MemAvailable+25%} --timeout 240s

Usually, in less than 5 minutes the backtrace listed below appears, followed
by a kernel panic:

| BUG: scheduling while atomic: kswapd1/181/0x00000002
|
| Preemption disabled at:
| [] zswap_frontswap_store+0x21a/0x6e1
|
| Kernel panic - not syncing: scheduling while atomic
| CPU: 14 PID: 181 Comm: kswapd1 Kdump: loaded Not tainted 5.0.14-rt9 #1
| Hardware name: AMD Pence/Pence, BIOS WPN2321X_Weekly_12_03_21 03/19/2012
| Call Trace:
|  panic+0x106/0x2a7
|  __schedule_bug.cold+0x3f/0x51
|  __schedule+0x5cb/0x6f0
|  schedule+0x43/0xd0
|  rt_spin_lock_slowlock_locked+0x114/0x2b0
|  rt_spin_lock_slowlock+0x51/0x80
|  zbud_alloc+0x1da/0x2d0
|  zswap_frontswap_store+0x31a/0x6e1
|  __frontswap_store+0xab/0x130
|  swap_writepage+0x39/0x70
|  pageout.isra.0+0xe3/0x320
|  shrink_page_list+0xa8e/0xd10
|  shrink_inactive_list+0x251/0x840
|  shrink_node_memcg+0x213/0x770
|  shrink_node+0xd9/0x450
|  balance_pgdat+0x2d5/0x510
|  kswapd+0x218/0x470
|  kthread+0xfb/0x130
|  ret_from_fork+0x27/0x50

Cc: stable-rt@vger.kernel.org
Reported-by: Ping Fang 
Signed-off-by: Luis Claudio R. Goncalves 
Reviewed-by: Daniel Bristot de Oliveira 
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Steven Rostedt (VMware)

futex: Delay deallocation of pi_state

2019-07-23T18:57:13+00:00

[ Upstream commit d7c7cf8cb68b7df17e6e50be1f25f35d83e686c7 ]

On -RT we can't invoke kfree() in a non-preemptible context.

Defer the deallocation of pi_state to preemptible context.

Signed-off-by: Thomas Gleixner 
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Steven Rostedt (VMware)

futex: Make the futex_hash_bucket lock raw

2019-07-23T18:57:13+00:00

[ Upstream commit f646521aadedab78801c9befe193e2e8a0c99298 ]

Since commit 1a1fb985f2e2b ("futex: Handle early deadlock return
correctly") we can deadlock while we attempt to acquire the HB lock if
we fail to acquire the lock.
The RT waiter (for the futex lock) is still enqueued and acquiring the
HB lock may build up a lock chain which leads to a deadlock if the owner
of the lock futex-lock holds the HB lock.

Make the hash bucket lock raw so it does not participate in the
lockchain.

Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Steven Rostedt (VMware)

Revert "futex: workaround migrate_disable/enable in different context"

2019-07-23T18:57:13+00:00

[ Upstream commit a71221d81cc4873891ae44f3aa02df596079b786 ]

Drop the RT fixup, the futex code will be changed to avoid the need for
the workaround.

Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Steven Rostedt (VMware)

Revert "rtmutex: Handle the various new futex race conditions"

2019-07-23T18:57:13+00:00

[ Upstream commit 9e0265c21af4d6388d47dcd5ce20f76ec3a2e468 ]

Drop the RT fixup, the futex code will be changed to avoid the need for
the workaround.

Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Steven Rostedt (VMware)

Revert "futex: Fix bug on when a requeued RT task times out"

2019-07-23T18:57:13+00:00

[ Upstream commit f1a170cb3289a48df26cae3c60d77608f7a988bb ]

Drop the RT fixup, the futex code will be changed to avoid the need for
the workaround.

Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Steven Rostedt (VMware)

Revert "futex: Ensure lock/unlock symetry versus pi_lock and hash bucket lock"

2019-07-23T18:57:13+00:00

[ Upstream commit 6a773b70cf105b46298ed3b44e77c102ce31d9ec ]

Drop the RT fixup, the futex code will be changed to avoid the need for
the workaround.

Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Steven Rostedt (VMware)

timers: Redo the notification of canceling timers on -RT

2019-07-23T18:57:13+00:00

[ Upstream commit c71273154c2ad12e13333aada340ff30e826a11b ]

Rework of the hrtimer, timer and posix-timer cancelation interface
on -RT. Instead of the swait/schedule interface we now have locks
which are taken while timer is active. During the cancellation of an
active timer the lock is acquired. The lock will then either
PI-boost the timer or block and wait until the timer completed.
The new code looks simpler and does not trigger a warning from
rcu_note_context_switch() anymore like reported by Grygorii Strashko
and Daniel Wagner.
The patches were contributed by Anna-Maria Gleixner.

This is an all in one commit of the following patches:
| [PATCH] timers: Introduce expiry spin lock
| [PATCH] timers: Drop expiry lock after each timer invocation
| [PATCH] hrtimer: Introduce expiry spin lock
| [PATCH] posix-timers: move rcu out of union
| [PATCH] posix-timers: Add expiry lock

Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Steven Rostedt (VMware)