perf_counter: SIGIO support

Provide support for fcntl() I/O availability signals.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <20090406094517.579788800@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 21 insertions, 1 deletions

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index f9d5cf0bfbdd..8d5d11b8d011 100644
--- a/include/linux/perf_counter.h
+++ b/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;
@@ -398,6 +399,7 @@ struct perf_counter {
 
         /* poll related */
         wait_queue_head_t               waitq;
+        struct fasync_struct            *fasync;
         /* optional: for NMIs */
         struct perf_wakeup_entry        wakeup;
 
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 727624db5078..c58cc64319e1 100644
--- a/kernel/perf_counter.c
+++ b/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_fops = {
         .unlocked_ioctl         = perf_ioctl,
         .compat_ioctl           = perf_ioctl,
         .mmap                   = perf_mmap,
+        .fasync                 = perf_fasync,
 };
 
 /*
@@ -1549,7 +1566,7 @@ void perf_counter_wakeup(struct perf_counter *counter)
         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_counter *counter)
         rcu_read_unlock();
 
         wake_up_all(&counter->waitq);
+        kill_fasync(&counter->fasync, SIGIO, POLL_IN);
 }
 
 /*