[ANNOUNCE] 4.4.6-rt13v4.4.6-rt13-patches

Dear RT folks!

I'm pleased to announce the v4.4.6-rt13 patch set.
Changes since v4.4.6-rt12:

- Alexandre Belloni sent patch for the AT91 to get rid of the free_irq()
  warning.

- Yang Shi sent a patch to address a "sleeping while atomic" warning in
  a writeback tracepoint. Until now it was disabled to avoid it, now it
  can be used again.

- Rik van Riel sent a patch to make the kvm async pagefault code use a
  simple wait queue.

- Mike Galbraith set a patch to address a "sleeping while atomic"
  warning in zsmalloc

- Netork packets sent by a RT task could be delayed (but won't block the
  RT task) if a task with lower priority was interruped while sending a
  packet. This is address by taking a qdisc lock so the high-prio task
  can boost a task with lower priority.

- Clark Williams reported a swait related complate_all() warning while
  comming out of suspend. Suspend to RAM (and hibernate) are now
  filtered out from the warning.

- Mike Galbraith sent a patch to address a "sleeping while atomic"
  warning in the zram driver.

- Josh Cartwright sent a patch to fix a lockdep splat in list_bl which
  was reported by Luis Claudio R. Goncalves.

Known issues:
  - CPU hotplug got a little better but can deadlock.

The delta patch against 4.4.6-rt12 is appended below and can be found here:

    https://cdn.kernel.org/pub/linux/kernel/projects/rt/4.4/incr/patch-4.4.6-rt12-rt13.patch.xz

You can get this release via the git tree at:

    git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git v4.4.6-rt13

The RT patch against 4.4.6 can be found here:

    https://cdn.kernel.org/pub/linux/kernel/projects/rt/4.4/patch-4.4.6-rt13.patch.xz

The split quilt queue is available at:

    https://cdn.kernel.org/pub/linux/kernel/projects/rt/4.4/patches-4.4.6-rt13.tar.xz

Sebastian

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

1 files changed, 175 insertions, 0 deletions

diff --git a/patches/drivers-block-zram-Replace-bit-spinlocks-with-rtmute.patch b/patches/drivers-block-zram-Replace-bit-spinlocks-with-rtmute.patch
new file mode 100644
index 000000000000..72c412350f53
--- /dev/null
+++ b/patches/drivers-block-zram-Replace-bit-spinlocks-with-rtmute.patch
@@ -0,0 +1,175 @@
+From: Mike Galbraith <umgwanakikbuti@gmail.com>
+Date: Thu, 31 Mar 2016 04:08:28 +0200
+Subject: [PATCH] drivers/block/zram: Replace bit spinlocks with rtmutex
+ for -rt
+
+They're nondeterministic, and lead to ___might_sleep() splats in -rt.
+OTOH, they're a lot less wasteful than an rtmutex per page.
+
+Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ drivers/block/zram/zram_drv.c |   30 ++++++++++++++++--------------
+ drivers/block/zram/zram_drv.h |   41 +++++++++++++++++++++++++++++++++++++++++
+ 2 files changed, 57 insertions(+), 14 deletions(-)
+
+--- a/drivers/block/zram/zram_drv.c
++++ b/drivers/block/zram/zram_drv.c
+@@ -520,6 +520,8 @@ static struct zram_meta *zram_meta_alloc
+ 		goto out_error;
+ 	}
+ 
++	zram_meta_init_table_locks(meta, disksize);
++
+ 	return meta;
+ 
+ out_error:
+@@ -568,12 +570,12 @@ static int zram_decompress_page(struct z
+ 	unsigned long handle;
+ 	size_t size;
+ 
+-	bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
++	zram_lock_table(&meta->table[index]);
+ 	handle = meta->table[index].handle;
+ 	size = zram_get_obj_size(meta, index);
+ 
+ 	if (!handle || zram_test_flag(meta, index, ZRAM_ZERO)) {
+-		bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
++		zram_unlock_table(&meta->table[index]);
+ 		clear_page(mem);
+ 		return 0;
+ 	}
+@@ -584,7 +586,7 @@ static int zram_decompress_page(struct z
+ 	else
+ 		ret = zcomp_decompress(zram->comp, cmem, size, mem);
+ 	zs_unmap_object(meta->mem_pool, handle);
+-	bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
++	zram_unlock_table(&meta->table[index]);
+ 
+ 	/* Should NEVER happen. Return bio error if it does. */
+ 	if (unlikely(ret)) {
+@@ -604,14 +606,14 @@ static int zram_bvec_read(struct zram *z
+ 	struct zram_meta *meta = zram->meta;
+ 	page = bvec->bv_page;
+ 
+-	bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
++	zram_lock_table(&meta->table[index]);
+ 	if (unlikely(!meta->table[index].handle) ||
+ 			zram_test_flag(meta, index, ZRAM_ZERO)) {
+-		bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
++		zram_unlock_table(&meta->table[index]);
+ 		handle_zero_page(bvec);
+ 		return 0;
+ 	}
+-	bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
++	zram_unlock_table(&meta->table[index]);
+ 
+ 	if (is_partial_io(bvec))
+ 		/* Use  a temporary buffer to decompress the page */
+@@ -689,10 +691,10 @@ static int zram_bvec_write(struct zram *
+ 		if (user_mem)
+ 			kunmap_atomic(user_mem);
+ 		/* Free memory associated with this sector now. */
+-		bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
++		zram_lock_table(&meta->table[index]);
+ 		zram_free_page(zram, index);
+ 		zram_set_flag(meta, index, ZRAM_ZERO);
+-		bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
++		zram_unlock_table(&meta->table[index]);
+ 
+ 		atomic64_inc(&zram->stats.zero_pages);
+ 		ret = 0;
+@@ -752,12 +754,12 @@ static int zram_bvec_write(struct zram *
+ 	 * Free memory associated with this sector
+ 	 * before overwriting unused sectors.
+ 	 */
+-	bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
++	zram_lock_table(&meta->table[index]);
+ 	zram_free_page(zram, index);
+ 
+ 	meta->table[index].handle = handle;
+ 	zram_set_obj_size(meta, index, clen);
+-	bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
++	zram_unlock_table(&meta->table[index]);
+ 
+ 	/* Update stats */
+ 	atomic64_add(clen, &zram->stats.compr_data_size);
+@@ -800,9 +802,9 @@ static void zram_bio_discard(struct zram
+ 	}
+ 
+ 	while (n >= PAGE_SIZE) {
+-		bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
++		zram_lock_table(&meta->table[index]);
+ 		zram_free_page(zram, index);
+-		bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
++		zram_unlock_table(&meta->table[index]);
+ 		atomic64_inc(&zram->stats.notify_free);
+ 		index++;
+ 		n -= PAGE_SIZE;
+@@ -928,9 +930,9 @@ static void zram_slot_free_notify(struct
+ 	zram = bdev->bd_disk->private_data;
+ 	meta = zram->meta;
+ 
+-	bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
++	zram_lock_table(&meta->table[index]);
+ 	zram_free_page(zram, index);
+-	bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
++	zram_unlock_table(&meta->table[index]);
+ 	atomic64_inc(&zram->stats.notify_free);
+ }
+ 
+--- a/drivers/block/zram/zram_drv.h
++++ b/drivers/block/zram/zram_drv.h
+@@ -72,6 +72,9 @@ enum zram_pageflags {
+ struct zram_table_entry {
+ 	unsigned long handle;
+ 	unsigned long value;
++#ifdef CONFIG_PREEMPT_RT_BASE
++	spinlock_t lock;
++#endif
+ };
+ 
+ struct zram_stats {
+@@ -119,4 +122,42 @@ struct zram {
+ 	 */
+ 	bool claim; /* Protected by bdev->bd_mutex */
+ };
++
++#ifndef CONFIG_PREEMPT_RT_BASE
++static inline void zram_lock_table(struct zram_table_entry *table)
++{
++	bit_spin_lock(ZRAM_ACCESS, &table->value);
++}
++
++static inline void zram_unlock_table(struct zram_table_entry *table)
++{
++	bit_spin_unlock(ZRAM_ACCESS, &table->value);
++}
++
++static inline void zram_meta_init_locks(struct zram_meta *meta, u64 disksize) { }
++#else /* CONFIG_PREEMPT_RT_BASE */
++static inline void zram_lock_table(struct zram_table_entry *table)
++{
++	spin_lock(&table->lock);
++	__set_bit(ZRAM_ACCESS, &table->value);
++}
++
++static inline void zram_unlock_table(struct zram_table_entry *table)
++{
++	__clear_bit(ZRAM_ACCESS, &table->value);
++	spin_unlock(&table->lock);
++}
++
++static inline void zram_meta_init_table_locks(struct zram_meta *meta, u64 disksize)
++{
++        size_t num_pages = disksize >> PAGE_SHIFT;
++        size_t index;
++
++        for (index = 0; index < num_pages; index++) {
++		spinlock_t *lock = &meta->table[index].lock;
++		spin_lock_init(lock);
++        }
++}
++#endif /* CONFIG_PREEMPT_RT_BASE */
++
+ #endif