linux-kernel - Re: [PATCH 2/6] RFC perf_counter: singleshot support

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Date:	Thu, 02 Apr 2009 14:18:11 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Paul Mackerras <paulus@...ba.org>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/6] RFC perf_counter: singleshot support

OK, so I just remembered the sigio thing mentioned by Paul a while back.

and this should do I suppose...

---
Subject: perf_counter: SIGIO support
From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Date: Thu Apr 02 14:15:54 CEST 2009


Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
 include/linux/perf_counter.h |    2 ++
 kernel/perf_counter.c        |   20 +++++++++++++++++++-
 2 files changed, 21 insertions(+), 1 deletion(-)

Index: linux-2.6/include/linux/perf_counter.h
===================================================================
--- linux-2.6.orig/include/linux/perf_counter.h
+++ linux-2.6/include/linux/perf_counter.h
@@ -238,6 +238,7 @@ enum perf_event_type {
 #include <linux/rcupdate.h>
 #include <linux/spinlock.h>
 #include <linux/hrtimer.h>
+#include <linux/fs.h>
 #include <asm/atomic.h>
 
 struct task_struct;
@@ -397,6 +398,7 @@ struct perf_counter {
 
 	/* poll related */
 	wait_queue_head_t		waitq;
+	struct fasync_struct		*fasync;
 	/* optional: for NMIs */
 	struct perf_wakeup_entry	wakeup;
 
Index: linux-2.6/kernel/perf_counter.c
===================================================================
--- linux-2.6.orig/kernel/perf_counter.c
+++ linux-2.6/kernel/perf_counter.c
@@ -1526,6 +1526,22 @@ out:
 	return ret;
 }
 
+static int perf_fasync(int fd, struct file *filp, int on)
+{
+	struct perf_counter *counter = filp->private_data;
+	struct inode *inode = filp->f_path.dentry->d_inode;
+	int retval;
+
+	mutex_lock(&inode->i_mutex);
+	retval = fasync_helper(fd, filp, on, &counter->fasync);
+	mutex_unlock(&inode->i_mutex);
+
+	if (retval < 0)
+		return retval;
+
+	return 0;
+}
+
 static const struct file_operations perf_fops = {
 	.release		= perf_release,
 	.read			= perf_read,
@@ -1533,6 +1549,7 @@ static const struct file_operations perf
 	.unlocked_ioctl		= perf_ioctl,
 	.compat_ioctl		= perf_ioctl,
 	.mmap			= perf_mmap,
+	.fasync			= perf_fasync,
 };
 
 /*
@@ -1549,7 +1566,7 @@ void perf_counter_wakeup(struct perf_cou
 	rcu_read_lock();
 	data = rcu_dereference(counter->data);
 	if (data) {
-		(void)atomic_xchg(&data->wakeup, POLL_IN);
+		atomic_set(&data->wakeup, POLL_IN);
 		/*
 		 * Ensure all data writes are issued before updating the
 		 * user-space data head information. The matching rmb()
@@ -1561,6 +1578,7 @@ void perf_counter_wakeup(struct perf_cou
 	rcu_read_unlock();
 
 	wake_up_all(&counter->waitq);
+	kill_fasync(&counter->fasync, SIGIO, POLL_IN);
 }
 
 /*


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