xtensa: add missing exclusive access state management

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: stable@vger.kernel.org
Fixes: f7c34874f04a ("xtensa: add exclusive atomics support")
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

diff --git a/arch/xtensa/include/asm/thread_info.h b/arch/xtensa/include/asm/thread_info.h
index 8918f0f20c53e0400be8fddcacf7c0af43947433..6acbbe0d87d3d2319cf1e7db5210ac4332763dab 100644 (file)
--- 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 33a257b33723aadcc19176f2d22b6d9391d8d30e..dc5c83cad9be85608f7730b1dfb9dde7b5b0f07e 100644 (file)
--- 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 98515c24d9b28058b2f93a66bff959a1598cd395..703cf6205efec6dd0d80b0dd60131627f8c25890 100644 (file)
--- 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