[PATCH RT 0/8] Linux 5.4.44-rt27-rc1

[PATCH RT 0/8] Linux 5.4.44-rt27-rc1

[Steven Rostedt]

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Dear RT Folks,

This is the RT stable review cycle of patch 5.4.44-rt27-rc1.

Please scream at me if I messed something up. Please test the patches too.

The -rc release will be uploaded to kernel.org and will be deleted when
the final release is out. This is just a review release (or release candidate).

The pre-releases will not be pushed to the git repository, only the
final release is.

If all goes well, this patch will be converted to the next main release
on 6/9/2020.

Enjoy,

-- Steve


To build 5.4.44-rt27-rc1 directly, the following patches should be applied:

  http://www.kernel.org/pub/linux/kernel/v5.x/linux-5.4.tar.xz

  http://www.kernel.org/pub/linux/kernel/v5.x/patch-5.4.44.xz

  http://www.kernel.org/pub/linux/kernel/projects/rt/5.4/patch-5.4.44-rt27-rc1.patch.xz

You can also build from 5.4.44-rt26 by applying the incremental patch:

http://www.kernel.org/pub/linux/kernel/projects/rt/5.4/incr/patch-5.4.44-rt26-rt27-rc1.patch.xz


Changes from 5.4.44-rt26:

---


John Ogness (1):
      printk: console must not schedule for drivers

Kevin Hao (1):
      mm: slub: Always flush the delayed empty slubs in flush_all()

Liwei Song (1):
      mm: Don't warn about atomic memory allocations during suspend

Sebastian Andrzej Siewior (3):
      fs/dcache: Include swait.h header
      Revert "rt: Improve the serial console PASS_LIMIT"
      mm/zswap: Use local lock to protect per-CPU data

Steven Rostedt (VMware) (1):
      Linux 5.4.44-rt27-rc1

汪勇10269566 (1):
      printk: Force a line break on pr_cont(" ")

----
 drivers/tty/serial/8250/8250_core.c | 11 +----------
 fs/proc/base.c                      |  1 +
 kernel/printk/printk.c              |  2 ++
 localversion-rt                     |  2 +-
 mm/slub.c                           | 11 +++++------
 mm/zswap.c                          | 21 ++++++++++++---------
 6 files changed, 22 insertions(+), 26 deletions(-)

[PATCH RT 1/8] printk: console must not schedule for drivers

[Steven Rostedt]

5.4.44-rt27-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: John Ogness <john.ogness@linutronix.de>

Even though the printk kthread is always preemptible, it is still not
allowed to call cond_resched() from within console drivers. The
task may become non-preemptible in the console driver call chain. For
example, vt_console_print() takes a spinlock and then can call into
fbcon_redraw(), which can conditionally invoke cond_resched():

|BUG: sleeping function called from invalid context at kernel/printk/printk.c:2322
|in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 177, name: printk
|CPU: 0 PID: 177 Comm: printk Not tainted 5.6.2-00011-ga536059557f1d9 #1
|Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
|Call Trace:
| dump_stack+0x66/0x8b
| ___might_sleep+0x102/0x120
| console_conditional_schedule+0x24/0x30
| fbcon_redraw+0x96/0x1c0
| fbcon_scroll+0x556/0xd70
| con_scroll+0x147/0x1e0
| lf+0x9e/0xb0
| vt_console_print+0x253/0x3d0
| printk_kthread_func+0x1d5/0x3b0

Disable cond_resched() for the call into the console drivers.

Reported-by: kernel test robot <rong.a.chen@intel.com>
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/printk/printk.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 2affe95866a4..9600373bcf55 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2746,6 +2746,7 @@ static int printk_kthread_func(void *data)
 			    &len, printk_time);
 
 		console_lock();
+		console_may_schedule = 0;
 		call_console_drivers(master_seq, ext_text, ext_len, text, len,
 				     msg->level, msg->facility);
 		if (len > 0 || ext_len > 0)
-- 
2.26.2

[PATCH RT 2/8] fs/dcache: Include swait.h header

[Steven Rostedt]

5.4.44-rt27-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

Include the swait.h header so it compiles even if not all patches are
applied.

Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 fs/proc/base.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 2dcd8fb3abb5..dc6cfa5de1df 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -95,6 +95,7 @@
 #include <linux/sched/stat.h>
 #include <linux/posix-timers.h>
 #include <trace/events/oom.h>
+#include <linux/swait.h>
 #include "internal.h"
 #include "fd.h"
 
-- 
2.26.2

[PATCH RT 3/8] Revert "rt: Improve the serial console PASS_LIMIT"

[Steven Rostedt]

5.4.44-rt27-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

There is no need to loop for longer. The message of too much work was
removed in commit
    9d7c249a1ef9b ("serial: 8250: drop the printk from serial8250_interrupt()")

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 drivers/tty/serial/8250/8250_core.c | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index 809a65f68028..02bfafa8a672 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -55,16 +55,7 @@ static struct uart_driver serial8250_reg;
 
 static unsigned int skip_txen_test; /* force skip of txen test at init time */
 
-/*
- * On -rt we can have a more delays, and legitimately
- * so - so don't drop work spuriously and spam the
- * syslog:
- */
-#ifdef CONFIG_PREEMPT_RT
-# define PASS_LIMIT	1000000
-#else
-# define PASS_LIMIT	512
-#endif
+#define PASS_LIMIT	512
 
 #include <asm/serial.h>
 /*
-- 
2.26.2

[PATCH RT 4/8] mm: Dont warn about atomic memory allocations during suspend

[Steven Rostedt]

5.4.44-rt27-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Liwei Song <liwei.song@windriver.com>

The ACPI code allocates larger amount of memory during resume. This
triggers a warning because the allocation happens with disabled
interrupts.
At this stage only one CPU is active so there should be no lock
contention. If SLUB needs to call into the buddy allocator for more
memory then it should not enable interrupts.

Limit the check to system state with more CPUs and scheduling and only
enable interrupts in SLUB at this stage.

Signed-off-by: Liwei Song <liwei.song@windriver.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
[bigeasy: commit description, allocate_slab() hunk]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 mm/slub.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index 44a602fc8a16..bea18bbae247 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -1635,7 +1635,7 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node)
 		enableirqs = true;
 
 #ifdef CONFIG_PREEMPT_RT
-	if (system_state > SYSTEM_BOOTING)
+	if (system_state > SYSTEM_BOOTING && system_state < SYSTEM_SUSPEND)
 		enableirqs = true;
 #endif
 	if (enableirqs)
@@ -2751,7 +2751,8 @@ static __always_inline void *slab_alloc_node(struct kmem_cache *s,
 	unsigned long tid;
 
 	if (IS_ENABLED(CONFIG_PREEMPT_RT) && IS_ENABLED(CONFIG_DEBUG_ATOMIC_SLEEP))
-		WARN_ON_ONCE(!preemptible() && system_state >= SYSTEM_SCHEDULING);
+		WARN_ON_ONCE(!preemptible() &&
+			     (system_state > SYSTEM_BOOTING && system_state < SYSTEM_SUSPEND));
 
 	s = slab_pre_alloc_hook(s, gfpflags);
 	if (!s)
@@ -3216,7 +3217,8 @@ int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t size,
 	int i;
 
 	if (IS_ENABLED(CONFIG_PREEMPT_RT) && IS_ENABLED(CONFIG_DEBUG_ATOMIC_SLEEP))
-		WARN_ON_ONCE(!preemptible() && system_state >= SYSTEM_SCHEDULING);
+		WARN_ON_ONCE(!preemptible() &&
+			     (system_state > SYSTEM_BOOTING && system_state < SYSTEM_SUSPEND));
 
 	/* memcg and kmem_cache debug support */
 	s = slab_pre_alloc_hook(s, flags);
-- 
2.26.2

[PATCH RT 5/8] mm: slub: Always flush the delayed empty slubs in flush_all()

[Steven Rostedt]

5.4.44-rt27-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Kevin Hao <haokexin@gmail.com>

After commit f0b231101c94 ("mm/SLUB: delay giving back empty slubs to
IRQ enabled regions"), when the free_slab() is invoked with the IRQ
disabled, the empty slubs are moved to a per-CPU list and will be
freed after IRQ enabled later. But in the current codes, there is
a check to see if there really has the cpu slub on a specific cpu
before flushing the delayed empty slubs, this may cause a reference
of already released kmem_cache in a scenario like below:
	cpu 0				cpu 1
  kmem_cache_destroy()
    flush_all()
                         --->IPI       flush_cpu_slab()
                                         flush_slab()
                                           deactivate_slab()
                                             discard_slab()
                                               free_slab()
                                             c->page = NULL;
      for_each_online_cpu(cpu)
        if (!has_cpu_slab(1, s))
          continue
        this skip to flush the delayed
        empty slub released by cpu1
    kmem_cache_free(kmem_cache, s)

                                       kmalloc()
                                         __slab_alloc()
                                            free_delayed()
                                            __free_slab()
                                            reference to released kmem_cache

Fixes: f0b231101c94 ("mm/SLUB: delay giving back empty slubs to IRQ enabled regions")
Signed-off-by: Kevin Hao <haokexin@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: stable-rt@vger.kernel.org
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 mm/slub.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index bea18bbae247..b2809a9ca8f8 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2382,9 +2382,6 @@ static void flush_all(struct kmem_cache *s)
 	for_each_online_cpu(cpu) {
 		struct slub_free_list *f;
 
-		if (!has_cpu_slab(cpu, s))
-			continue;
-
 		f = &per_cpu(slub_free_list, cpu);
 		raw_spin_lock_irq(&f->lock);
 		list_splice_init(&f->list, &tofree);
-- 
2.26.2

[PATCH RT 7/8] mm/zswap: Use local lock to protect per-CPU data

[Steven Rostedt]

5.4.44-rt27-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

This is an incremental update of the zswap patch. Addtional spots were
identified, which were lacking proper locking, during the rework of the
patch for upstream.
The complete patch description is available as commit
   79410590ae87e ("mm/zswap: Use local lock to protect per-CPU data")

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 mm/zswap.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/mm/zswap.c b/mm/zswap.c
index 21d2d3ed3d6d..3c9644b51f3f 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -372,6 +372,8 @@ static struct zswap_entry *zswap_entry_find_get(struct rb_root *root,
 * per-cpu code
 **********************************/
 static DEFINE_PER_CPU(u8 *, zswap_dstmem);
+/* Used for zswap_dstmem and tfm */
+static DEFINE_LOCAL_IRQ_LOCK(zswap_cpu_lock);
 
 static int zswap_dstmem_prepare(unsigned int cpu)
 {
@@ -889,10 +891,11 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
 		dlen = PAGE_SIZE;
 		src = (u8 *)zhdr + sizeof(struct zswap_header);
 		dst = kmap_atomic(page);
-		tfm = *get_cpu_ptr(entry->pool->tfm);
+		local_lock(zswap_cpu_lock);
+		tfm = *this_cpu_ptr(entry->pool->tfm);
 		ret = crypto_comp_decompress(tfm, src, entry->length,
 					     dst, &dlen);
-		put_cpu_ptr(entry->pool->tfm);
+		local_unlock(zswap_cpu_lock);
 		kunmap_atomic(dst);
 		BUG_ON(ret);
 		BUG_ON(dlen != PAGE_SIZE);
@@ -981,8 +984,6 @@ static void zswap_fill_page(void *ptr, unsigned long value)
 	memset_l(page, value, PAGE_SIZE / sizeof(unsigned long));
 }
 
-/* protect zswap_dstmem from concurrency */
-static DEFINE_LOCAL_IRQ_LOCK(zswap_dstmem_lock);
 /*********************************
 * frontswap hooks
 **********************************/
@@ -1060,7 +1061,8 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
 	}
 
 	/* compress */
-	dst = get_locked_var(zswap_dstmem_lock, zswap_dstmem);
+	local_lock(zswap_cpu_lock);
+	dst = *this_cpu_ptr(&zswap_dstmem);
 	tfm = *this_cpu_ptr(entry->pool->tfm);
 	src = kmap_atomic(page);
 	ret = crypto_comp_compress(tfm, src, PAGE_SIZE, dst, &dlen);
@@ -1088,7 +1090,7 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
 	memcpy(buf, &zhdr, hlen);
 	memcpy(buf + hlen, dst, dlen);
 	zpool_unmap_handle(entry->pool->zpool, handle);
-	put_locked_var(zswap_dstmem_lock, zswap_dstmem);
+	local_unlock(zswap_cpu_lock);
 
 	/* populate entry */
 	entry->offset = offset;
@@ -1116,7 +1118,7 @@ static int zswap_frontswap_store(unsigned type, pgoff_t offset,
 	return 0;
 
 put_dstmem:
-	put_locked_var(zswap_dstmem_lock, zswap_dstmem);
+	local_unlock(zswap_cpu_lock);
 	zswap_pool_put(entry->pool);
 freepage:
 	zswap_entry_cache_free(entry);
@@ -1161,9 +1163,10 @@ static int zswap_frontswap_load(unsigned type, pgoff_t offset,
 	if (zpool_evictable(entry->pool->zpool))
 		src += sizeof(struct zswap_header);
 	dst = kmap_atomic(page);
-	tfm = *get_cpu_ptr(entry->pool->tfm);
+	local_lock(zswap_cpu_lock);
+	tfm = *this_cpu_ptr(entry->pool->tfm);
 	ret = crypto_comp_decompress(tfm, src, entry->length, dst, &dlen);
-	put_cpu_ptr(entry->pool->tfm);
+	local_unlock(zswap_cpu_lock);
 	kunmap_atomic(dst);
 	zpool_unmap_handle(entry->pool->zpool, entry->handle);
 	BUG_ON(ret);
-- 
2.26.2

[PATCH RT 8/8] Linux 5.4.44-rt27-rc1

[Steven Rostedt]

5.4.44-rt27-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

---
 localversion-rt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/localversion-rt b/localversion-rt
index 2e9afd4a0afd..3b0c6038dae9 100644
--- a/localversion-rt
+++ b/localversion-rt
@@ -1 +1 @@
--rt26
+-rt27-rc1
-- 
2.26.2