Linux 4.1 added the possibility of perf_event_open() returning
EBUSY if an existing exclusive event controls the PMU.

This was introduced by the following commit:

        commit bed5b25ad9c8a2f5d735ef0bc746ec870c01c1b0
        Author: Alexander Shishkin <[email protected]>
        Date:   Fri Jan 30 12:31:06 2015 +0200

        perf: Add a pmu capability for "exclusive" events

        Signed-off-by: Alexander Shishkin <[email protected]>
        Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
        Cc: Borislav Petkov <[email protected]>
        Cc: Frederic Weisbecker <[email protected]>
        Cc: H. Peter Anvin <[email protected]>
        Cc: Kaixu Xia <[email protected]>
        Cc: Linus Torvalds <[email protected]>
        Cc: Mike Galbraith <[email protected]>
        Cc: Paul Mackerras <[email protected]>
        Cc: Robert Richter <[email protected]>
        Cc: Stephane Eranian <[email protected]>
        Cc: Thomas Gleixner <[email protected]>
        Cc: [email protected]
        Cc: [email protected]
        Cc: [email protected]
        Cc: [email protected]
        Cc: [email protected]

Signed-off-by: Vince Weaver <[email protected]>

diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2
index b3cd93f..3d03786 100644
--- a/man2/perf_event_open.2
+++ b/man2/perf_event_open.2
@@ -2911,6 +2911,11 @@ the cgroup file descriptor in
 .I pid
 is not valid.
 .TP
+.BR EBUSY " (since Linux 4.1)"
+.\" bed5b25ad9c8a2f5d735ef0bc746ec870c01c1b0
+Returned if another event already has exclusive
+access to the PMU.
+.TP
 .B EFAULT
 Returned if the
 .I attr
--
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