+/*
+ * Change the DS configuration from tracing prev to tracing next.
+ */
+void ds_switch_to(struct task_struct *prev, struct task_struct *next)
+{
+ struct ds_context *prev_ctx = prev->thread.ds_ctx;
+ struct ds_context *next_ctx = next->thread.ds_ctx;
+
+ if (prev_ctx) {
+ update_debugctlmsr(0);
+
+ if (prev_ctx->bts_master &&
+ (prev_ctx->bts_master->trace.ds.flags & BTS_TIMESTAMPS)) {
+ struct bts_struct ts = {
+ .qualifier = bts_task_departs,
+ .variant.timestamp.jiffies = jiffies_64,
+ .variant.timestamp.pid = prev->pid
+ };
+ bts_write(prev_ctx->bts_master, &ts);
+ }
+ }
+
+ if (next_ctx) {
+ if (next_ctx->bts_master &&
+ (next_ctx->bts_master->trace.ds.flags & BTS_TIMESTAMPS)) {
+ struct bts_struct ts = {
+ .qualifier = bts_task_arrives,
+ .variant.timestamp.jiffies = jiffies_64,
+ .variant.timestamp.pid = next->pid
+ };
+ bts_write(next_ctx->bts_master, &ts);
+ }
+
+ wrmsrl(MSR_IA32_DS_AREA, (unsigned long)next_ctx->ds);
+ }
+
+ update_debugctlmsr(next->thread.debugctlmsr);
+}
+
+void ds_copy_thread(struct task_struct *tsk, struct task_struct *father)
+{
+ clear_tsk_thread_flag(tsk, TIF_DS_AREA_MSR);
+ tsk->thread.ds_ctx = NULL;
+}
+
+void ds_exit_thread(struct task_struct *tsk)