perf_event_open.2: tfix

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man2/perf_event_open.2

@@ -1132,7 +1132,7 @@ types choose watermark and set
 .I wakeup_watermark
 to 1.
 
-Prior to Linux 3.0 setting
+Prior to Linux 3.0, setting
 .\" commit f506b3dc0ec454a16d40cab9ee5d75435b39dc50
 .I wakeup_events
 to 0 resulted in no overflow notifications;
@@ -2587,7 +2587,7 @@ or
 .BR epoll (7).
 Alternatively, the overflow events can be captured via sa signal handler,
 by enabling I/O signaling on the file descriptor; see the discussion of the
-.BF F_SETOWN
+.BR F_SETOWN
 and
 .BR F_SETSIG
 operations in
@@ -2605,7 +2605,7 @@ or
 .I wakeup_watermark
 value that will trigger if a certain number of samples
 or bytes have been written to the mmap ring buffer.
-In this case
+In this case,
 .B POLL_IN
 is indicated.
 
@@ -2649,7 +2649,7 @@ to calculate event values can be found in that section.
 Originally, when rdpmc support was enabled, any process (not just ones
 with an active perf event) could use the rdpmc instruction to access
 the counters.
-Starting with Linux 4.0
+Starting with Linux 4.0,
 .\" 7911d3f7af14a614617e38245fedf98a724e46a9
 rdpmc support is only allowed if an event is currently enabled
 in a process's context.
@@ -2732,7 +2732,7 @@ after the next overflow.
 The argument is a pointer to a 64-bit value containing the
 desired new period.
 
-Prior to Linux 2.6.36
+Prior to Linux 2.6.36,
 .\" commit ad0cf3478de8677f720ee06393b3147819568d6a
 this ioctl always failed due to a bug
 in the kernel.
@@ -2770,7 +2770,7 @@ The argument is a BPF program file descriptor that was created by
 a previous
 .BR bpf (2)
 system call.
-.SS Using prctl
+.SS Using prctl(2)
 A process can enable or disable all the event groups that are
 attached to it using the
 .BR prctl (2)