[PATCH 1/6] Move out seqcount from seqlock.h
From: Stefani Seibold
Create a seperate seqcount.h file which handles only seqcount. This file
is save to include in VDSO, since there is no in-kernel functionality
like spinlock in use. seqlock.h still includes seqcount.h, so there is no
side effect for current users.
Signed-off-by: Stefani Seibold
---
include/linux/seqcount.h | 150 +++
include/linux/seqlock.h | 145 +
2 files changed, 151 insertions(+), 144 deletions(-)
create mode 100644 include/linux/seqcount.h
diff --git a/include/linux/seqcount.h b/include/linux/seqcount.h
new file mode 100644
index 000..b83dff3
--- /dev/null
+++ b/include/linux/seqcount.h
@@ -0,0 +1,150 @@
+/*
+ * Version using sequence counter only.
+ * This can be used when code has its own mutex protecting the
+ * updating starting before the write_seqcountbeqin() and ending
+ * after the write_seqcount_end().
+ */
+
+#ifndef __LINUX_SEQCOUNT_H
+#define __LINUX_SEQCOUNT_H
+
+#include
+#include
+
+typedef struct seqcount {
+ unsigned sequence;
+} seqcount_t;
+
+#define SEQCNT_ZERO { 0 }
+#define seqcount_init(x) do { *(x) = (seqcount_t) SEQCNT_ZERO; } while (0)
+
+/**
+ * __read_seqcount_begin - begin a seq-read critical section (without barrier)
+ * @s: pointer to seqcount_t
+ * Returns: count to be passed to read_seqcount_retry
+ *
+ * __read_seqcount_begin is like read_seqcount_begin, but has no smp_rmb()
+ * barrier. Callers should ensure that smp_rmb() or equivalent ordering is
+ * provided before actually loading any of the variables that are to be
+ * protected in this critical section.
+ *
+ * Use carefully, only in critical code, and comment how the barrier is
+ * provided.
+ */
+static inline unsigned __read_seqcount_begin(const seqcount_t *s)
+{
+ unsigned ret;
+
+repeat:
+ ret = ACCESS_ONCE(s->sequence);
+ if (unlikely(ret & 1)) {
+ cpu_relax();
+ goto repeat;
+ }
+ return ret;
+}
+
+/**
+ * read_seqcount_begin - begin a seq-read critical section
+ * @s: pointer to seqcount_t
+ * Returns: count to be passed to read_seqcount_retry
+ *
+ * read_seqcount_begin opens a read critical section of the given seqcount.
+ * Validity of the critical section is tested by checking read_seqcount_retry
+ * function.
+ */
+static inline unsigned read_seqcount_begin(const seqcount_t *s)
+{
+ unsigned ret = __read_seqcount_begin(s);
+ smp_rmb();
+ return ret;
+}
+
+/**
+ * raw_seqcount_begin - begin a seq-read critical section
+ * @s: pointer to seqcount_t
+ * Returns: count to be passed to read_seqcount_retry
+ *
+ * raw_seqcount_begin opens a read critical section of the given seqcount.
+ * Validity of the critical section is tested by checking read_seqcount_retry
+ * function.
+ *
+ * Unlike read_seqcount_begin(), this function will not wait for the count
+ * to stabilize. If a writer is active when we begin, we will fail the
+ * read_seqcount_retry() instead of stabilizing at the beginning of the
+ * critical section.
+ */
+static inline unsigned raw_seqcount_begin(const seqcount_t *s)
+{
+ unsigned ret = ACCESS_ONCE(s->sequence);
+ smp_rmb();
+ return ret & ~1;
+}
+
+/**
+ * __read_seqcount_retry - end a seq-read critical section (without barrier)
+ * @s: pointer to seqcount_t
+ * @start: count, from read_seqcount_begin
+ * Returns: 1 if retry is required, else 0
+ *
+ * __read_seqcount_retry is like read_seqcount_retry, but has no smp_rmb()
+ * barrier. Callers should ensure that smp_rmb() or equivalent ordering is
+ * provided before actually loading any of the variables that are to be
+ * protected in this critical section.
+ *
+ * Use carefully, only in critical code, and comment how the barrier is
+ * provided.
+ */
+static inline int __read_seqcount_retry(const seqcount_t *s, unsigned start)
+{
+ return unlikely(s->sequence != start);
+}
+
+/**
+ * read_seqcount_retry - end a seq-read critical section
+ * @s: pointer to seqcount_t
+ * @start: count, from read_seqcount_begin
+ * Returns: 1 if retry is required, else 0
+ *
+ * read_seqcount_retry closes a read critical section of the given seqcount.
+ * If the critical section was invalid, it must be ignored (and typically
+ * retried).
+ */
+static inline int read_seqcount_retry(const seqcount_t *s, unsigned start)
+{
+ smp_rmb();
+
+ return __read_seqcount_retry(s, start);
+}
+
+
+/*
+ * Sequence counter only version assumes that callers are using their
+ * own mutexing.
+ */
+static inline void write_seqcount_begin(seqcount_t *s)
+{
+ s->sequence++;
+ smp_wmb();
+}
+
+static inline void write_seqcount_end(seqcount_t *s)
+{
+ smp_wmb();
+ s->sequence++;
+}
+
+/**
+ * write_seqcount_barrier - invalidate in-progress read-side seq operations
+ * @s: pointer to seqcount_t
+ *
+ * After write_seqcount_barrier, no read-side seq operations will complete
+ * successfully and see data older
[PATCH 1/6] Move out seqcount from seqlock.h
From: Stefani Seibold stef...@seibold.net
Create a seperate seqcount.h file which handles only seqcount. This file
is save to include in VDSO, since there is no in-kernel functionality
like spinlock in use. seqlock.h still includes seqcount.h, so there is no
side effect for current users.
Signed-off-by: Stefani Seibold stef...@seibold.net
---
include/linux/seqcount.h | 150 +++
include/linux/seqlock.h | 145 +
2 files changed, 151 insertions(+), 144 deletions(-)
create mode 100644 include/linux/seqcount.h
diff --git a/include/linux/seqcount.h b/include/linux/seqcount.h
new file mode 100644
index 000..b83dff3
--- /dev/null
+++ b/include/linux/seqcount.h
@@ -0,0 +1,150 @@
+/*
+ * Version using sequence counter only.
+ * This can be used when code has its own mutex protecting the
+ * updating starting before the write_seqcountbeqin() and ending
+ * after the write_seqcount_end().
+ */
+
+#ifndef __LINUX_SEQCOUNT_H
+#define __LINUX_SEQCOUNT_H
+
+#include asm/processor.h
+#include asm/barrier.h
+
+typedef struct seqcount {
+ unsigned sequence;
+} seqcount_t;
+
+#define SEQCNT_ZERO { 0 }
+#define seqcount_init(x) do { *(x) = (seqcount_t) SEQCNT_ZERO; } while (0)
+
+/**
+ * __read_seqcount_begin - begin a seq-read critical section (without barrier)
+ * @s: pointer to seqcount_t
+ * Returns: count to be passed to read_seqcount_retry
+ *
+ * __read_seqcount_begin is like read_seqcount_begin, but has no smp_rmb()
+ * barrier. Callers should ensure that smp_rmb() or equivalent ordering is
+ * provided before actually loading any of the variables that are to be
+ * protected in this critical section.
+ *
+ * Use carefully, only in critical code, and comment how the barrier is
+ * provided.
+ */
+static inline unsigned __read_seqcount_begin(const seqcount_t *s)
+{
+ unsigned ret;
+
+repeat:
+ ret = ACCESS_ONCE(s-sequence);
+ if (unlikely(ret 1)) {
+ cpu_relax();
+ goto repeat;
+ }
+ return ret;
+}
+
+/**
+ * read_seqcount_begin - begin a seq-read critical section
+ * @s: pointer to seqcount_t
+ * Returns: count to be passed to read_seqcount_retry
+ *
+ * read_seqcount_begin opens a read critical section of the given seqcount.
+ * Validity of the critical section is tested by checking read_seqcount_retry
+ * function.
+ */
+static inline unsigned read_seqcount_begin(const seqcount_t *s)
+{
+ unsigned ret = __read_seqcount_begin(s);
+ smp_rmb();
+ return ret;
+}
+
+/**
+ * raw_seqcount_begin - begin a seq-read critical section
+ * @s: pointer to seqcount_t
+ * Returns: count to be passed to read_seqcount_retry
+ *
+ * raw_seqcount_begin opens a read critical section of the given seqcount.
+ * Validity of the critical section is tested by checking read_seqcount_retry
+ * function.
+ *
+ * Unlike read_seqcount_begin(), this function will not wait for the count
+ * to stabilize. If a writer is active when we begin, we will fail the
+ * read_seqcount_retry() instead of stabilizing at the beginning of the
+ * critical section.
+ */
+static inline unsigned raw_seqcount_begin(const seqcount_t *s)
+{
+ unsigned ret = ACCESS_ONCE(s-sequence);
+ smp_rmb();
+ return ret ~1;
+}
+
+/**
+ * __read_seqcount_retry - end a seq-read critical section (without barrier)
+ * @s: pointer to seqcount_t
+ * @start: count, from read_seqcount_begin
+ * Returns: 1 if retry is required, else 0
+ *
+ * __read_seqcount_retry is like read_seqcount_retry, but has no smp_rmb()
+ * barrier. Callers should ensure that smp_rmb() or equivalent ordering is
+ * provided before actually loading any of the variables that are to be
+ * protected in this critical section.
+ *
+ * Use carefully, only in critical code, and comment how the barrier is
+ * provided.
+ */
+static inline int __read_seqcount_retry(const seqcount_t *s, unsigned start)
+{
+ return unlikely(s-sequence != start);
+}
+
+/**
+ * read_seqcount_retry - end a seq-read critical section
+ * @s: pointer to seqcount_t
+ * @start: count, from read_seqcount_begin
+ * Returns: 1 if retry is required, else 0
+ *
+ * read_seqcount_retry closes a read critical section of the given seqcount.
+ * If the critical section was invalid, it must be ignored (and typically
+ * retried).
+ */
+static inline int read_seqcount_retry(const seqcount_t *s, unsigned start)
+{
+ smp_rmb();
+
+ return __read_seqcount_retry(s, start);
+}
+
+
+/*
+ * Sequence counter only version assumes that callers are using their
+ * own mutexing.
+ */
+static inline void write_seqcount_begin(seqcount_t *s)
+{
+ s-sequence++;
+ smp_wmb();
+}
+
+static inline void write_seqcount_end(seqcount_t *s)
+{
+ smp_wmb();
+ s-sequence++;
+}
+
+/**
+ * write_seqcount_barrier - invalidate in-progress read-side seq operations
+ * @s: pointer to seqcount_t
+ *
+ * After write_seqcount_barrier, no read-side seq
