The result of the s32ex opcode is recorded in the ATOMCTL special
register and must be retrieved with the getex opcode. Context switch
between s32ex and getex may trash the ATOMCTL register and result in
duplicate update or missing update of the atomic variable.
Add atomctl8 field to the struct thread_info and use getex to swap
ATOMCTL bit 8 as a part of context switch.
Clear exclusive access monitor on kernel entry.
Cc: [email protected]
Fixes: f7c34874f04a ("xtensa: add exclusive atomics support")
Signed-off-by: Max Filippov <[email protected]>
---
arch/xtensa/include/asm/thread_info.h | 4 ++++
arch/xtensa/kernel/asm-offsets.c | 3 +++
arch/xtensa/kernel/entry.S | 11 +++++++++++
3 files changed, 18 insertions(+)
diff --git a/arch/xtensa/include/asm/thread_info.h b/arch/xtensa/include/asm/thread_info.h
index 8918f0f20c53..6acbbe0d87d3 100644
--- a/arch/xtensa/include/asm/thread_info.h
+++ b/arch/xtensa/include/asm/thread_info.h
@@ -55,6 +55,10 @@ struct thread_info {
mm_segment_t addr_limit; /* thread address space */
unsigned long cpenable;
+#if XCHAL_HAVE_EXCLUSIVE
+ /* result of the most recent exclusive store */
+ unsigned long atomctl8;
+#endif
/* Allocate storage for extra user states and coprocessor states. */
#if XTENSA_HAVE_COPROCESSORS
diff --git a/arch/xtensa/kernel/asm-offsets.c b/arch/xtensa/kernel/asm-offsets.c
index 33a257b33723..dc5c83cad9be 100644
--- a/arch/xtensa/kernel/asm-offsets.c
+++ b/arch/xtensa/kernel/asm-offsets.c
@@ -93,6 +93,9 @@ int main(void)
DEFINE(THREAD_RA, offsetof (struct task_struct, thread.ra));
DEFINE(THREAD_SP, offsetof (struct task_struct, thread.sp));
DEFINE(THREAD_CPENABLE, offsetof (struct thread_info, cpenable));
+#if XCHAL_HAVE_EXCLUSIVE
+ DEFINE(THREAD_ATOMCTL8, offsetof (struct thread_info, atomctl8));
+#endif
#if XTENSA_HAVE_COPROCESSORS
DEFINE(THREAD_XTREGS_CP0, offsetof(struct thread_info, xtregs_cp.cp0));
DEFINE(THREAD_XTREGS_CP1, offsetof(struct thread_info, xtregs_cp.cp1));
diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S
index 98515c24d9b2..703cf6205efe 100644
--- a/arch/xtensa/kernel/entry.S
+++ b/arch/xtensa/kernel/entry.S
@@ -374,6 +374,11 @@ common_exception:
s32i a2, a1, PT_LCOUNT
#endif
+#if XCHAL_HAVE_EXCLUSIVE
+ /* Clear exclusive access monitor set by interrupted code */
+ clrex
+#endif
+
/* It is now save to restore the EXC_TABLE_FIXUP variable. */
rsr a2, exccause
@@ -2020,6 +2025,12 @@ ENTRY(_switch_to)
s32i a3, a4, THREAD_CPENABLE
#endif
+#if XCHAL_HAVE_EXCLUSIVE
+ l32i a3, a5, THREAD_ATOMCTL8
+ getex a3
+ s32i a3, a4, THREAD_ATOMCTL8
+#endif
+
/* Flush register file. */
spill_registers_kernel
--
2.20.1