Linux 4.9.61-rt52-rc1

PATCH New Steven Rostedt 1 participant 5 messages Nov 21, 2017

Subsystems (4)

VFS Block layer TPM device driver zram

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Steven Rostedt

author

2017-11-21 16:05 UTC #0 lore raw

cover Linux 4.9.61-rt52-rc1

Dear RT Folks,

This is the RT stable review cycle of patch 4.9.61-rt52-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 11/27/2017.

Enjoy,

-- Steve

To build 4.9.61-rt52-rc1 directly, the following patches should be applied:

http://www.kernel.org/pub/linux/kernel/v4.x/linux-4.9.tar.xz

http://www.kernel.org/pub/linux/kernel/v4.x/patch-4.9.61.xz

http://www.kernel.org/pub/linux/kernel/projects/rt/4.9/patch-4.9.61-rt52-rc1.patch.xz

You can also build from 4.9.61-rt51 by applying the incremental patch:

http://www.kernel.org/pub/linux/kernel/projects/rt/4.9/incr/patch-4.9.61-rt51-rt52-rc1.patch.xz

Changes from 4.9.61-rt51:

---

Haris Okanovic (1):
tpm_tis: fix stall after iowrite*()s

Mike Galbraith (1):
drivers/zram: fix zcomp_stream_get() smp_processor_id() use in preemptible code

Sebastian Andrzej Siewior (1):
fs/dcache: disable preemption on i_dir_seq's write side

Steven Rostedt (VMware) (1):

      Linux 4.9.61-rt52-rc1

----

 drivers/block/zram/zcomp.c |  3 ++-
 drivers/char/tpm/tpm_tis.c | 29 +++++++++++++++++++++++++++--
 fs/dcache.c                | 12 +++++++-----
 fs/inode.c                 |  2 +-
 fs/libfs.c                 |  6 ++++--
 include/linux/fs.h         |  2 +-
 localversion-rt            |  2 +-
 7 files changed, 43 insertions(+), 13 deletions(-)

Steven Rostedt

author

2017-11-21 16:04 UTC #1 lore raw

PATCH 1/4 drivers/zram: fix zcomp_stream_get() smp_processor_id() use in preemptible code

4.9.61-rt52-rc1 stable review patch.
If anyone has any objections, please let me know.

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

From: Mike Galbraith <[email protected]>

Use get_local_ptr() instead this_cpu_ptr() to avoid a warning regarding smp_processor_id() in preemptible code.
raw_cpu_ptr() would be fine, too because the per-CPU data structure is protected with a spin lock so it does not matter much if we take the other one.

Cc [email protected]

Signed-off-by Mike Galbraith <[email protected]>

Signed-off-by Sebastian Andrzej Siewior <[email protected]>

Signed-off-by Steven Rostedt (VMware) <[email protected]>

---
 drivers/block/zram/zcomp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

drivers/block/zram/zcomp.c +2 -1

index fa8329ad79fd..8c93ee150ee8 100644
@@ -120,7 +120,7 @@ struct zcomp_strm *zcomp_stream_get(struct zcomp *comp)
 {
 	struct zcomp_strm *zstrm;
 
-	zstrm = *this_cpu_ptr(comp->stream);
+	zstrm = *get_local_ptr(comp->stream);
 	spin_lock(&zstrm->zcomp_lock);
 	return zstrm;
 }

@@ -131,6 +131,7 @@ void zcomp_stream_put(struct zcomp *comp)
 
 	zstrm = *this_cpu_ptr(comp->stream);
 	spin_unlock(&zstrm->zcomp_lock);
+	put_local_ptr(zstrm);
 }
 
 int zcomp_compress(struct zcomp_strm *zstrm,

Signature · 1 line

2.13.2

Steven Rostedt

author

2017-11-21 16:04 UTC #2 lore raw

PATCH 2/4 fs/dcache: disable preemption on i_dir_seqs write side

In reply to Steven Rostedt

4.9.61-rt52-rc1 stable review patch.
If anyone has any objections, please let me know.

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

From: Sebastian Andrzej Siewior <[email protected]>

i_dir_seq is an opencoded seqcounter. Based on the code it looks like we could have two writers in parallel despite the fact that the d_lock is held. The problem is that during the write process on RT the preemption is still enabled and if this process is interrupted by a reader with RT priority then we lock up.
To avoid that lock up I am disabling the preemption during the update. The rename of i_dir_seq is here to ensure to catch new write sides in future.

Cc [email protected]

Reported-by [email protected]

Signed-off-by Sebastian Andrzej Siewior <[email protected]>

Signed-off-by Steven Rostedt (VMware) <[email protected]>

---
 fs/dcache.c        | 12 +++++++-----
 fs/inode.c         |  2 +-
 fs/libfs.c         |  6 ++++--
 include/linux/fs.h |  2 +-
 4 files changed, 13 insertions(+), 9 deletions(-)

fs/dcache.c +7 -5

index 37948da28742..f0719b2f1be5 100644
@@ -2409,9 +2409,10 @@ EXPORT_SYMBOL(d_rehash);
 static inline unsigned start_dir_add(struct inode *dir)
 {
 
+	preempt_disable_rt();
 	for (;;) {
-		unsigned n = dir->i_dir_seq;
-		if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n)
+		unsigned n = dir->__i_dir_seq;
+		if (!(n & 1) && cmpxchg(&dir->__i_dir_seq, n, n + 1) == n)
 			return n;
 		cpu_relax();
 	}

@@ -2419,7 +2420,8 @@ static inline unsigned start_dir_add(struct inode *dir)
 
 static inline void end_dir_add(struct inode *dir, unsigned n)
 {
-	smp_store_release(&dir->i_dir_seq, n + 2);
+	smp_store_release(&dir->__i_dir_seq, n + 2);
+	preempt_enable_rt();
 }
 
 static void d_wait_lookup(struct dentry *dentry)

@@ -2455,7 +2457,7 @@ struct dentry *d_alloc_parallel(struct dentry *parent,
 
 retry:
 	rcu_read_lock();
-	seq = smp_load_acquire(&parent->d_inode->i_dir_seq) & ~1;
+	seq = smp_load_acquire(&parent->d_inode->__i_dir_seq) & ~1;
 	r_seq = read_seqbegin(&rename_lock);
 	dentry = __d_lookup_rcu(parent, name, &d_seq);
 	if (unlikely(dentry)) {

@@ -2477,7 +2479,7 @@ struct dentry *d_alloc_parallel(struct dentry *parent,
 		goto retry;
 	}
 	hlist_bl_lock(b);
-	if (unlikely(parent->d_inode->i_dir_seq != seq)) {
+	if (unlikely(parent->d_inode->__i_dir_seq != seq)) {
 		hlist_bl_unlock(b);
 		rcu_read_unlock();
 		goto retry;

fs/inode.c +1 -1

index 920aa0b1c6b0..3d6b5fd1bf06 100644
@@ -153,7 +153,7 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
 	inode->i_bdev = NULL;
 	inode->i_cdev = NULL;
 	inode->i_link = NULL;
-	inode->i_dir_seq = 0;
+	inode->__i_dir_seq = 0;
 	inode->i_rdev = 0;
 	inode->dirtied_when = 0;

fs/libfs.c +4 -2

index 48826d4da189..3ea54d1fc431 100644
@@ -89,7 +89,7 @@ static struct dentry *next_positive(struct dentry *parent,
 				    struct list_head *from,
 				    int count)
 {
-	unsigned *seq = &parent->d_inode->i_dir_seq, n;
+	unsigned *seq = &parent->d_inode->__i_dir_seq, n;
 	struct dentry *res;
 	struct list_head *p;
 	bool skipped;

@@ -122,8 +122,9 @@ static struct dentry *next_positive(struct dentry *parent,
 static void move_cursor(struct dentry *cursor, struct list_head *after)
 {
 	struct dentry *parent = cursor->d_parent;
-	unsigned n, *seq = &parent->d_inode->i_dir_seq;
+	unsigned n, *seq = &parent->d_inode->__i_dir_seq;
 	spin_lock(&parent->d_lock);
+	preempt_disable_rt();
 	for (;;) {
 		n = *seq;
 		if (!(n & 1) && cmpxchg(seq, n, n + 1) == n)

@@ -136,6 +137,7 @@ static void move_cursor(struct dentry *cursor, struct list_head *after)
 	else
 		list_add_tail(&cursor->d_child, &parent->d_subdirs);
 	smp_store_release(seq, n + 2);
+	preempt_enable_rt();
 	spin_unlock(&parent->d_lock);
 }

include/linux/fs.h +1 -1

index d705ae084edd..ab1946f4a729 100644
@@ -688,7 +688,7 @@ struct inode {
 		struct block_device	*i_bdev;
 		struct cdev		*i_cdev;
 		char			*i_link;
-		unsigned		i_dir_seq;
+		unsigned		__i_dir_seq;
 	};
 
 	__u32			i_generation;

Signature · 1 line

2.13.2

Steven Rostedt

author

2017-11-21 16:04 UTC #3 lore raw

PATCH 3/4 tpm_tis: fix stall after iowrite*()s

In reply to Steven Rostedt

4.9.61-rt52-rc1 stable review patch.
If anyone has any objections, please let me know.

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

From: Haris Okanovic <[email protected]>

ioread8() operations to TPM MMIO addresses can stall the cpu when immediately following a sequence of iowrite*()'s to the same region.

For example, cyclitest measures ~400us latency spikes when a non-RT usermode application communicates with an SPI-based TPM chip (Intel Atom E3940 system, PREEMPT_RT_FULL kernel). The spikes are caused by a stalling ioread8() operation following a sequence of 30+ iowrite8()s to the same address. I believe this happens because the write sequence is buffered (in cpu or somewhere along the bus), and gets flushed on the first LOAD instruction (ioread*()) that follows.

The enclosed change appears to fix this issue: read the TPM chip's access register (status code) after every iowrite*() operation to amortize the cost of flushing data to chip across multiple instructions.

Cc [email protected]

Signed-off-by Haris Okanovic <[email protected]>

Signed-off-by Sebastian Andrzej Siewior <[email protected]>

Signed-off-by Steven Rostedt (VMware) <[email protected]>

---
 drivers/char/tpm/tpm_tis.c | 29 +++++++++++++++++++++++++++--
 1 file changed, 27 insertions(+), 2 deletions(-)

drivers/char/tpm/tpm_tis.c +27 -2

index 8022bea27fed..247330efd310 100644
@@ -50,6 +50,31 @@ static inline struct tpm_tis_tcg_phy *to_tpm_tis_tcg_phy(struct tpm_tis_data *da
 	return container_of(data, struct tpm_tis_tcg_phy, priv);
 }
 
+#ifdef CONFIG_PREEMPT_RT_FULL
+/*
+ * Flushes previous write operations to chip so that a subsequent
+ * ioread*()s won't stall a cpu.
+ */
+static inline void tpm_tis_flush(void __iomem *iobase)
+{
+	ioread8(iobase + TPM_ACCESS(0));
+}
+#else
+#define tpm_tis_flush(iobase) do { } while (0)
+#endif
+
+static inline void tpm_tis_iowrite8(u8 b, void __iomem *iobase, u32 addr)
+{
+	iowrite8(b, iobase + addr);
+	tpm_tis_flush(iobase);
+}
+
+static inline void tpm_tis_iowrite32(u32 b, void __iomem *iobase, u32 addr)
+{
+	iowrite32(b, iobase + addr);
+	tpm_tis_flush(iobase);
+}
+
 static bool interrupts = true;
 module_param(interrupts, bool, 0444);
 MODULE_PARM_DESC(interrupts, "Enable interrupts");

@@ -103,7 +128,7 @@ static int tpm_tcg_write_bytes(struct tpm_tis_data *data, u32 addr, u16 len,
 	struct tpm_tis_tcg_phy *phy = to_tpm_tis_tcg_phy(data);
 
 	while (len--)
-		iowrite8(*value++, phy->iobase + addr);
+		tpm_tis_iowrite8(*value++, phy->iobase, addr);
 	return 0;
 }

@@ -127,7 +152,7 @@ static int tpm_tcg_write32(struct tpm_tis_data *data, u32 addr, u32 value)
 {
 	struct tpm_tis_tcg_phy *phy = to_tpm_tis_tcg_phy(data);
 
-	iowrite32(value, phy->iobase + addr);
+	tpm_tis_iowrite32(value, phy->iobase, addr);
 	return 0;
 }

Signature · 1 line

2.13.2

Steven Rostedt

author

2017-11-21 16:04 UTC #4 lore raw

PATCH 4/4 Linux 4.9.61-rt52-rc1

In reply to Steven Rostedt

4.9.61-rt52-rc1 stable review patch.
If anyone has any objections, please let me know.

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

From: "Steven Rostedt (VMware)" <[email protected]>

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

localversion-rt +1 -1

index 75493460c41f..d42746076d9b 100644
@@ -1 +1 @@
--rt51
+-rt52-rc1

Signature · 1 line

2.13.2