1 files changed, 30 insertions, 8 deletions

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 00263c9e6500..08a9df08adba 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -239,6 +239,14 @@ void exit_thread(void)
                 t->io_bitmap_max = 0;
                 put_cpu();
         }
+#ifdef CONFIG_X86_DS
+        /* Free any DS contexts that have not been properly released. */
+        if (unlikely(t->ds_ctx)) {
+                /* we clear debugctl to make sure DS is not used. */
+                update_debugctlmsr(0);
+                ds_free(t->ds_ctx);
+        }
+#endif /* CONFIG_X86_DS */
 }
 
 void flush_thread(void)
@@ -472,13 +480,27 @@ static inline void __switch_to_xtra(struct task_struct *prev_p,
         next = &next_p->thread;
 
         debugctl = prev->debugctlmsr;
-        if (next->ds_area_msr != prev->ds_area_msr) {
-                /* we clear debugctl to make sure DS
-                 * is not in use when we change it */
-                debugctl = 0;
-                update_debugctlmsr(0);
-                wrmsrl(MSR_IA32_DS_AREA, next->ds_area_msr);
+
+#ifdef CONFIG_X86_DS
+        {
+                unsigned long ds_prev = 0, ds_next = 0;
+
+                if (prev->ds_ctx)
+                        ds_prev = (unsigned long)prev->ds_ctx->ds;
+                if (next->ds_ctx)
+                        ds_next = (unsigned long)next->ds_ctx->ds;
+
+                if (ds_next != ds_prev) {
+                        /*
+                         * We clear debugctl to make sure DS
+                         * is not in use when we change it:
+                         */
+                        debugctl = 0;
+                        update_debugctlmsr(0);
+                        wrmsrl(MSR_IA32_DS_AREA, ds_next);
+                }
         }
+#endif /* CONFIG_X86_DS */
 
         if (next->debugctlmsr != debugctl)
                 update_debugctlmsr(next->debugctlmsr);
@@ -516,13 +538,13 @@ static inline void __switch_to_xtra(struct task_struct *prev_p,
                 memset(tss->io_bitmap, 0xff, prev->io_bitmap_max);
         }
 
-#ifdef X86_BTS
+#ifdef CONFIG_X86_PTRACE_BTS
         if (test_tsk_thread_flag(prev_p, TIF_BTS_TRACE_TS))
                 ptrace_bts_take_timestamp(prev_p, BTS_TASK_DEPARTS);
 
         if (test_tsk_thread_flag(next_p, TIF_BTS_TRACE_TS))
                 ptrace_bts_take_timestamp(next_p, BTS_TASK_ARRIVES);
-#endif
+#endif /* CONFIG_X86_PTRACE_BTS */
 }
 
 /*