perfmon2 minimal v2: monitoring activation

Index: o/perfmon/perfmon_activate.c
===================================================================
@@ -0,0 +1,136 @@
+/*
+ * perfmon_activate.c: perfmon2 start/stop functions
+ *
+ * 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
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ * 02111-1307 USA
+ */
+#include <linux/kernel.h>
+#include <linux/perfmon_kern.h>
+#include "perfmon_priv.h"
+
+/**
+ * __pfm_start - activate monitoring
+ * @ctx: context to operate on
+ * @start: pfarg_start as passed by user
+ *
+ * When operating in per-thread mode and not self-monitoring, the monitored
+ * thread must be stopped. Activation will be effective next time the thread
+ * is context switched in.
+ *
+ * The pfarg_start argument is optional and may be used to designate
+ * the initial event set to activate. When not provided, the last active
+ * set is used. For the first activation, set0 is used when start is NULL.
+ *
+ * On some architectures, e.g., IA-64, it may be possible to start monitoring
+ * without calling this function under certain conditions (per-thread and self
+ * monitoring). In this case, either set0 or the last active set is used.
+ *
+ * the context is locked and interrupts are disabled.
+ */
+int __pfm_start(struct pfm_context *ctx)
+{
+	struct task_struct *task;
+	struct pfm_event_set *set;
+
+	task = ctx->task;
+
+	/*
+	 * UNLOADED: error
+	 * LOADED  : normal start, nop if started unless set is different
+	 * ZOMBIE  : cannot happen
+	 */
+	if (ctx->state == PFM_CTX_UNLOADED)
+		return -EINVAL;
+
+	set = ctx->active_set;
+
+	/*
+	 * mark as started
+	 * must be done before calling pfm_arch_start()
+	 */
+	ctx->flags.started = 1;
+
+	pfm_arch_start(task, ctx);
+
+	/*
+	 * we check whether we had a pending ovfl before restarting.
+	 * If so we need to regenerate the interrupt to make sure we
+	 * keep recorded samples. For non-self monitoring this check
+	 * is done in the pfm_ctxswin_thread() routine.
+	 *
+	 * we check new_set/old_set because pfm_switch_sets() already
+	 * takes care of replaying the pending interrupts
+	 */
+	if (task == current && set->npend_ovfls)
+		pfm_arch_resend_irq(ctx);
+
+	return 0;
+}
+
+/**
+ * __pfm_stop - stop monitoring
+ * @ctx: context to operate on
+ *
+ * When operating in per-thread* mode and when not self-monitoring,
+ * the monitored thread must be stopped.
+ *
+ * the context is locked and interrupts are disabled.
+ */
+int __pfm_stop(struct pfm_context *ctx)
+{
+	struct task_struct *task;
+
+	/*
+	 * context must be attached (zombie cannot happen)
+	 */
+	if (ctx->state == PFM_CTX_UNLOADED)
+		return -EINVAL;
+
+	task = ctx->task;
+
+	PFM_DBG("ctx_task=[%d] ctx_state=%d is_system=%d",
+		task ? task->pid : -1,
+		ctx->state,
+		!task);
+
+	pfm_arch_stop(task, ctx);
+
+	ctx->flags.started = 0;
+	/*
+	 * starting now, in-flight PMU interrupt for this context
+	 * are treated as spurious
+	 */
+	return 0;
+}

Index: o/perfmon/perfmon_priv.h
===================================================================
@@ -57,6 +57,9 @@
 
 void pfm_free_context(struct pfm_context *ctx);
 
+int __pfm_stop(struct pfm_context *ctx);
+int __pfm_start(struct pfm_context *ctx);
+
 ssize_t pfm_sysfs_res_show(char *buf, size_t sz, int what);
 
 int pfm_pmu_acquire(void);