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authorSang-Heon Jeon <ekffu200098@gmail.com>2026-08-24 01:18:14 +0900
committerJulia Lawall <Julia.Lawall@inria.fr>2026-08-23 22:12:11 +0200
commit2bd30b8dc75b823dd7bbef9d7bc68e1fd7ecee5c (patch)
treedcc4da1d99f17541c5590ac63c77da4bf372a4ab /include/vdso/helpers.h
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coccinelle: alloc_cast: drop removed allocatorsgrafted
- pci_alloc_consistent() and pci_zalloc_consistent() were removed by commit 7968778914e5 ("PCI: Remove the deprecated "pci-dma-compat.h" API") - kmem_alloc() was removed by commit f078d4ea8276 ("xfs: convert kmem_alloc() to kmalloc()") - kmem_zalloc() was removed by commit 10634530f7ba ("xfs: convert kmem_zalloc() to kzalloc()") - kmem_zone_alloc() and kmem_zone_zalloc() were removed by commit bae633a4a283 ("xfs: remove xfs_zone_{alloc,zalloc} helpers") So drop them from the rules. No functional change. Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com> Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Diffstat (limited to 'include/vdso/helpers.h')
-rw-r--r--include/vdso/helpers.h116
1 files changed, 116 insertions, 0 deletions
diff --git a/include/vdso/helpers.h b/include/vdso/helpers.h
new file mode 100644
index 000000000..65151b681
--- /dev/null
+++ b/include/vdso/helpers.h
@@ -0,0 +1,116 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __VDSO_HELPERS_H
+#define __VDSO_HELPERS_H
+
+#ifndef __ASSEMBLER__
+
+#include <asm/barrier.h>
+#include <vdso/datapage.h>
+#include <vdso/processor.h>
+#include <vdso/clocksource.h>
+
+static __always_inline bool vdso_is_timens_clock(const struct vdso_clock *vc)
+{
+ return IS_ENABLED(CONFIG_TIME_NS) && vc->clock_mode == VDSO_CLOCKMODE_TIMENS;
+}
+
+static __always_inline u32 vdso_read_begin(const struct vdso_clock *vc)
+{
+ u32 seq;
+
+ while (unlikely((seq = READ_ONCE(vc->seq)) & 1))
+ cpu_relax();
+
+ smp_rmb();
+ return seq;
+}
+
+/*
+ * Variant of vdso_read_begin() to handle VDSO_CLOCKMODE_TIMENS.
+ *
+ * Time namespace enabled tasks have a special VVAR page installed which has
+ * vc->seq set to 1 and vc->clock_mode set to VDSO_CLOCKMODE_TIMENS. For non
+ * time namespace affected tasks this does not affect performance because if
+ * vc->seq is odd, i.e. a concurrent update is in progress the extra check for
+ * vc->clock_mode is just a few extra instructions while spin waiting for
+ * vc->seq to become even again.
+ */
+static __always_inline bool vdso_read_begin_timens(const struct vdso_clock *vc, u32 *seq)
+{
+ while (unlikely((*seq = READ_ONCE(vc->seq)) & 1)) {
+ if (vdso_is_timens_clock(vc))
+ return true;
+ cpu_relax();
+ }
+ smp_rmb();
+
+ return false;
+}
+
+static __always_inline u32 vdso_read_retry(const struct vdso_clock *vc,
+ u32 start)
+{
+ u32 seq;
+
+ smp_rmb();
+ seq = READ_ONCE(vc->seq);
+ return unlikely(seq != start);
+}
+
+static __always_inline void vdso_write_seq_begin(struct vdso_clock *vc)
+{
+ /*
+ * WRITE_ONCE() is required otherwise the compiler can validly tear
+ * updates to vc->seq and it is possible that the value seen by the
+ * reader is inconsistent.
+ */
+ WRITE_ONCE(vc->seq, vc->seq + 1);
+}
+
+static __always_inline void vdso_write_seq_end(struct vdso_clock *vc)
+{
+ /*
+ * WRITE_ONCE() is required otherwise the compiler can validly tear
+ * updates to vc->seq and it is possible that the value seen by the
+ * reader is inconsistent.
+ */
+ WRITE_ONCE(vc->seq, vc->seq + 1);
+}
+
+static __always_inline void vdso_write_begin_clock(struct vdso_clock *vc)
+{
+ vdso_write_seq_begin(vc);
+ /* Ensure the sequence invalidation is visible before data is modified */
+ smp_wmb();
+}
+
+static __always_inline void vdso_write_end_clock(struct vdso_clock *vc)
+{
+ /* Ensure the data update is visible before the sequence is set valid again */
+ smp_wmb();
+ vdso_write_seq_end(vc);
+}
+
+static __always_inline void vdso_write_begin(struct vdso_time_data *vd)
+{
+ struct vdso_clock *vc = vd->clock_data;
+
+ vdso_write_seq_begin(&vc[CS_HRES_COARSE]);
+ vdso_write_seq_begin(&vc[CS_RAW]);
+ /* Ensure the sequence invalidation is visible before data is modified */
+ smp_wmb();
+}
+
+static __always_inline void vdso_write_end(struct vdso_time_data *vd)
+{
+ struct vdso_clock *vc = vd->clock_data;
+
+ /* Ensure the data update is visible before the sequence is set valid again */
+ smp_wmb();
+ vdso_write_seq_end(&vc[CS_HRES_COARSE]);
+ vdso_write_seq_end(&vc[CS_RAW]);
+}
+
+#endif /* !__ASSEMBLER__ */
+
+#endif /* __VDSO_HELPERS_H */