This patch contains the PMU context switch routines.
--- linux-2.6.17.1.orig/perfmon/perfmon_ctxsw.c 1969-12-31 16:00:00.000000000 -0800
+++ linux-2.6.17.1/perfmon/perfmon_ctxsw.c 2006-06-21 04:22:51.000000000 -0700
@@ -0,0 +1,381 @@
+/*
+ * perfmon_cxtsw.c: perfmon2 context switch code
+ *
+ * This file implements the perfmon2 interface which
+ * provides access to the hardware performance counters
+ * of the host processor.
+ *
+ * The initial version of perfmon.c was written by
+ * Ganesh Venkitachalam, IBM Corp.
+ *
+ * Then it was modified for perfmon-1.x by Stephane Eranian and
+ * David Mosberger, Hewlett Packard Co.
+ *
+ * Version Perfmon-2.x is a complete rewrite of perfmon-1.x
+ * by Stephane Eranian, Hewlett Packard Co.
+ *
+ * Copyright (c) 1999-2006 Hewlett-Packard Development Company, L.P.
+ * Contributed by Stephane Eranian <[email protected]>
+ * David Mosberger-Tang <[email protected]>
+ *
+ * More information about perfmon available at:
+ * http://www.hpl.hp.com/research/linux/perfmon
+ */
+#include <linux/kernel.h>
+#include <linux/perfmon.h>
+
+#ifdef CONFIG_SMP
+/*
+ * interrupts are masked, runqueue lock is held, context is locked
+ */
+void pfm_ctxswin_thread(struct task_struct *task, struct pfm_context *ctx,
+ struct pfm_event_set *set, int must_reload)
+{
+ u64 cur_act;
+ int reload_pmcs, reload_pmds;
+
+ BUG_ON(task->pid == 0);
+ BUG_ON(__get_cpu_var(pmu_owner));
+
+ BUG_ON(task->pfm_context != ctx);
+
+ cur_act = __get_cpu_var(pmu_activation_number);
+
+ /*
+ * in case fo zombie, we do not complete ctswin of the
+ * PMU, and we force a call to pfm_handle_work() to finish
+ * cleanup, i.e., free context + smpl_buff. The reason for
+ * deferring to pfm_handle_work() is that it is not possible
+ * to vfree() with interrupts disabled.
+ */
+ if (unlikely(ctx->state == PFM_CTX_ZOMBIE)) {
+ struct thread_info *th_info;
+
+ /*
+ * ensure everything is properly stopped
+ */
+ __pfm_stop(ctx);
+
+ ctx->flags.trap_reason = PFM_TRAP_REASON_ZOMBIE;
+ th_info = task->thread_info;
+ set_bit(TIF_NOTIFY_RESUME, &th_info->flags);
+
+ return;
+ }
+
+ if (set->flags & PFM_SETFL_TIME_SWITCH)
+ __get_cpu_var(pfm_syst_info) = PFM_CPUINFO_TIME_SWITCH;
+ctx->last_cpu=-1;
+ /*
+ * if we were the last user of the PMU on that CPU,
+ * then nothing to do except restore psr
+ */
+ if (ctx->last_cpu == smp_processor_id() && ctx->last_act == cur_act) {
+ /*
+ * check for forced reload conditions
+ */
+ reload_pmcs = set->priv_flags & PFM_SETFL_PRIV_MOD_PMCS;
+ reload_pmds = set->priv_flags & PFM_SETFL_PRIV_MOD_PMDS;
+ } else {
+ reload_pmcs = 1;
+ reload_pmds = 1;
+ }
+ /* consumed */
+ set->priv_flags &= ~PFM_SETFL_PRIV_MOD_BOTH;
+
+ if (reload_pmds)
+ pfm_arch_restore_pmds(ctx, set);
+
+ /*
+ * need to check if had in-flight interrupt in
+ * pfm_ctxswout_thread(). If at least one bit set, then we must replay
+ * the interrupt to avoid loosing some important performance data.
+ */
+ if (set->npend_ovfls) {
+ pfm_arch_resend_irq();
+ __get_cpu_var(pfm_stats).pfm_ovfl_intr_replay_count++;
+ }
+
+ if (reload_pmcs)
+ pfm_arch_restore_pmcs(ctx, set);
+
+ /*
+ * record current activation for this context
+ */
+ pfm_inc_activation();
+ pfm_set_last_cpu(ctx, smp_processor_id());
+ pfm_set_activation(ctx);
+
+ /*
+ * establish new ownership.
+ */
+ pfm_set_pmu_owner(task, ctx);
+
+ pfm_arch_ctxswin(task, ctx, set);
+}
+#else /* !CONFIG_SMP */
+/*
+ * interrupts are disabled
+ */
+void pfm_ctxswin_thread(struct task_struct *task, struct pfm_context *ctx,
+ struct pfm_event_set *set, int force_reload)
+{
+ u32 set_priv_flags;
+
+ set_priv_flags = set->priv_flags;
+
+ if (set->flags & PFM_SETFL_TIME_SWITCH) {
+ __get_cpu_var(pfm_syst_info) = PFM_CPUINFO_TIME_SWITCH;
+ }
+
+ /*
+ * must force reload due to lazy save
+ */
+ if (force_reload)
+ set_priv_flags |= PFM_SETFL_PRIV_MOD_BOTH;
+
+ /*
+ * check what needs to be restored.
+ * If owner == task, our state is still live and we could
+ * just reactivate and go. However, we need to check for the
+ * following conditions:
+ * - pmu owner != task
+ * - PMDs were modified
+ * - PMCs were modified
+ * - arch modifies PMC to stop monitoring
+ * - there was an in-flight interrupt at pfm_ctxswout_thread()
+ *
+ * if anyone of these is true, we cannot take the short path, i.e,
+ * just restore info + arch_ctxswin and return
+ */
+ if (set_priv_flags & PFM_SETFL_PRIV_MOD_PMDS)
+ pfm_arch_restore_pmds(ctx, set);
+
+ /*
+ * need to check if had in-flight interrupt at time of pfm_ctxswout_thread().
+ * If at least one bit set, then we must replay the interrupt to avoid
+ * losing some important performance data.
+ */
+ if (set->npend_ovfls) {
+ pfm_arch_resend_irq();
+ __get_cpu_var(pfm_stats).pfm_ovfl_intr_replay_count++;
+ }
+
+ if (set_priv_flags & PFM_SETFL_PRIV_MOD_PMCS)
+ pfm_arch_restore_pmcs(ctx, set);
+
+ set->priv_flags &= ~PFM_SETFL_PRIV_MOD_BOTH;
+
+ /*
+ * establish new ownership.
+ */
+ pfm_set_pmu_owner(task, ctx);
+
+ /*
+ * reactivate monitoring
+ */
+ pfm_arch_ctxswin(task, ctx, set);
+}
+#endif /* !CONFIG_SMP */
+
+static void pfm_ctxswin_sys(struct task_struct *task, struct pfm_context *ctx,
+ struct pfm_event_set *set)
+{
+ unsigned long info;
+
+ info = __get_cpu_var(pfm_syst_info);
+
+ /*
+ * don't do anything before started
+ */
+ if (ctx->flags.started == 0)
+ return;
+
+ /*
+ * pid 0 is guaranteed to be the idle task. There is one such task with pid 0
+ * on each CPU, so we can rely on the pid to identify the idle task.
+ */
+ if (task->pid == 0 && (set->flags & PFM_SETFL_EXCL_IDLE) != 0)
+ pfm_arch_stop(task ,ctx, set);
+ else
+ pfm_arch_ctxswin(task, ctx, set);
+}
+
+void __pfm_ctxswin(struct task_struct *task)
+{
+ struct pfm_context *ctx, *ctxp;
+ struct pfm_event_set *set;
+ int must_force_reload = 0;
+ u64 now_itc;
+
+ ctxp = __get_cpu_var(pmu_ctx);
+ ctx = task->pfm_context;
+
+ /*
+ * system-wide : pmu_ctx must not be NULL to proceed
+ * per-thread UP: pmu_ctx may be NULL if no left-over owner
+ * per-thread SMP: pmu_ctx is always NULL coming in
+ */
+ if (ctxp == NULL && ctx == NULL)
+ return;
+
+#ifdef CONFIG_SMP
+ /*
+ * if ctxp != 0, it means we are in system-wide mode.
+ * thereore ctx is NULL (mutual exclusion)
+ */
+ if (ctxp)
+ ctx = ctxp;
+#else
+ /*
+ * someone used the PMU, first push it out and
+ * then we'll be able to install our stuff !
+ */
+ if (ctxp && ctxp->flags.system)
+ ctx = ctxp;
+ else if (ctx) {
+ if (ctxp && ctxp != ctx) {
+ pfm_save_pmds_release(ctxp);
+ must_force_reload = 1;
+ }
+ } else
+ return;
+#endif
+ spin_lock(&ctx->lock);
+
+ set = ctx->active_set;
+
+ if (ctx->flags.system)
+ pfm_ctxswin_sys(task, ctx, set);
+ else
+ pfm_ctxswin_thread(task, ctx, set, must_force_reload);
+
+ /*
+ * ctx->duration does count even when context in MASKED state
+ * set->duration does not count when context in MASKED state.
+ * But the set->duration_start is reset in unmask_monitoring()
+ */
+
+ now_itc = pfm_arch_get_itc();
+
+ ctx->duration_start = now_itc;
+ set->duration_start = now_itc;
+
+ spin_unlock(&ctx->lock);
+}
+
+/*
+ * interrupts are masked, runqueue lock is held.
+ *
+ * In UP. we simply stop monitoring and leave the state
+ * in place, i.e., lazy save
+ */
+void pfm_ctxswout_thread(struct task_struct *task, struct pfm_context *ctx,
+ struct pfm_event_set *set)
+{
+ BUG_ON(task->pfm_context != ctx);
+
+ /*
+ * stop monitoring and collect any pending
+ * overflow information into set_povfl_pmds
+ * and set_npend_ovfls for use on ctxswin_thread()
+ * to potentially replay the PMU interrupt
+ *
+ * The key point is that we cannot afford to loose a PMU
+ * interrupt. We cannot cancel in-flight interrupts, therefore
+ * we let them happen and be treated as spurious and then we
+ * replay them on ctxsw in.
+ */
+ pfm_arch_ctxswout(task, ctx, set);
+
+#ifdef CONFIG_SMP
+ /*
+ * release ownership of this PMU.
+ * PM interrupts are masked, so nothing
+ * can happen.
+ */
+ pfm_set_pmu_owner(NULL, NULL);
+
+ /*
+ * we systematically save the PMD that we effectively
+ * use. In SMP, we have no guarantee we will be scheduled
+ * on the same CPU again.
+ */
+ pfm_modview_begin(set);
+ pfm_arch_save_pmds(ctx, set);
+ pfm_modview_end(set);
+#endif
+
+ /*
+ * clear cpuinfo, cpuinfo is used in
+ * per task mode with the set time switch flag.
+ */
+ __get_cpu_var(pfm_syst_info) = 0;
+}
+
+static void pfm_ctxswout_sys(struct task_struct *task, struct pfm_context *ctx,
+ struct pfm_event_set *set)
+{
+ /*
+ * do nothing before started
+ * XXX: assumes cannot be started from user level
+ */
+ if (ctx->flags.started == 0)
+ return;
+
+ /*
+ * restore monitoring if set has EXCL_IDLE and task was idle task
+ */
+ if (task->pid == 0 && (set->flags & PFM_SETFL_EXCL_IDLE) != 0) {
+ pfm_arch_start(task, ctx, set);
+ } else {
+ pfm_arch_ctxswout(task, ctx, set);
+ }
+}
+
+/*
+ * we come here on every context switch out.
+ */
+void __pfm_ctxswout(struct task_struct *task)
+{
+ struct pfm_context *ctx;
+ struct pfm_event_set *set;
+ u64 now_itc, diff;
+
+ ctx = __get_cpu_var(pmu_ctx);
+ if (ctx == NULL)
+ return;
+
+ now_itc = pfm_arch_get_itc();
+
+ spin_lock(&ctx->lock);
+
+ set = ctx->active_set;
+
+ if (ctx->flags.system) {
+ pfm_ctxswout_sys(task, ctx, set);
+ } else {
+ /*
+ * in UP, due to lazy save, we may have a
+ * context loaded onto the PMU BUT it may not
+ * be the one from the current task. In that case
+ * simply skip everything else
+ */
+ if (task->pfm_context == NULL)
+ goto done;
+
+ pfm_ctxswout_thread(task, ctx, set);
+ }
+
+ diff = now_itc - ctx->duration_start;
+ ctx->duration += diff;
+
+ /*
+ * accumulate only when set is actively monitoring,
+ */
+ if (ctx->state == PFM_CTX_LOADED)
+ set->duration += now_itc - set->duration_start;
+
+done:
+ spin_unlock(&ctx->lock);
+}
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