locking: Introduce prepare_sync_core_cmd()

Introduce an architecture function that architectures can use to set
up ("prepare") SYNC_CORE commands.

The function will be used by RISC-V to update its "deferred icache-
flush" data structures (icache_stale_mask).

Architectures defining prepare_sync_core_cmd() static inline need to
select ARCH_HAS_PREPARE_SYNC_CORE_CMD.

Suggested-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Andrea Parri <parri.andrea@gmail.com>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/r/20240131144936.29190-4-parri.andrea@gmail.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/include/linux/sync_core.h b/include/linux/sync_core.h
index 013da4b8b3272c6aff56a84cc40ce8d8a5d17041..67bb9794b87585c5d4584205879fbcb469fa0469 100644 (file)
--- a/include/linux/sync_core.h
+++ b/include/linux/sync_core.h
@@ -17,5 +17,19 @@ static inline void sync_core_before_usermode(void)
 }
 #endif
 
-#endif /* _LINUX_SYNC_CORE_H */
+#ifdef CONFIG_ARCH_HAS_PREPARE_SYNC_CORE_CMD
+#include <asm/sync_core.h>
+#else
+/*
+ * This is a dummy prepare_sync_core_cmd() implementation that can be used on
+ * all architectures which provide unconditional core serializing instructions
+ * in switch_mm().
+ * If your architecture doesn't provide such core serializing instructions in
+ * switch_mm(), you may need to write your own functions.
+ */
+static inline void prepare_sync_core_cmd(struct mm_struct *mm)
+{
+}
+#endif
 
+#endif /* _LINUX_SYNC_CORE_H */

diff --git a/init/Kconfig b/init/Kconfig
index 8df18f3a974846b48e41b2a8dcbc2f2f2f90128e..c3994b92333ded7989a672cf0e594896debfad67 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1970,6 +1970,9 @@ source "kernel/Kconfig.locks"
 config ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
        bool
 
+config ARCH_HAS_PREPARE_SYNC_CORE_CMD
+       bool
+
 config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
        bool
 

diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
index f3d91628d6b8ab5f98ace3b211ac2d2cd74e30f2..6d1f31b3a967b3d3fd8ac0ee6a316ea9f4ae3b56 100644 (file)
--- a/kernel/sched/membarrier.c
+++ b/kernel/sched/membarrier.c
@@ -320,6 +320,7 @@ static int membarrier_private_expedited(int flags, int cpu_id)
                      MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY))
                        return -EPERM;
                ipi_func = ipi_sync_core;
+               prepare_sync_core_cmd(mm);
        } else if (flags == MEMBARRIER_FLAG_RSEQ) {
                if (!IS_ENABLED(CONFIG_RSEQ))
                        return -EINVAL;