From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 29 Jul 2021 12:52:14 +0200
Subject: [PATCH] arm64/sve: Delay freeing memory in fpsimd_flush_thread()

fpsimd_flush_thread() invokes kfree() via sve_free() within a preempt disabled
section which is not working on -RT.

Delay freeing of memory until preemption is enabled again.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/arm64/kernel/fpsimd.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1141,6 +1141,8 @@ static void fpsimd_flush_thread_vl(enum
 
 void fpsimd_flush_thread(void)
 {
+	void *sve_state = NULL;
+
 	if (!system_supports_fpsimd())
 		return;
 
@@ -1152,11 +1154,16 @@ void fpsimd_flush_thread(void)
 
 	if (system_supports_sve()) {
 		clear_thread_flag(TIF_SVE);
-		sve_free(current);
+
+		/* Defer kfree() while in atomic context */
+		sve_state = current->thread.sve_state;
+		current->thread.sve_state = NULL;
+
 		fpsimd_flush_thread_vl(ARM64_VEC_SVE);
 	}
 
 	put_cpu_fpsimd_context();
+	kfree(sve_state);
 }
 
 /*