[PATCH] tkill.2: document EAGAIN error for real-time signals

[Jann Horn <jannh@xxxxxxxxxx>]

See __send_signal() in kernel/signal.c:

if (sig >= SIGRTMIN && info->si_code != SI_USER) {
  /*
   * Queue overflow, abort.  We may abort if the
   * signal was rt and sent by user using something
   * other than kill().
   */
  result = TRACE_SIGNAL_OVERFLOW_FAIL;
  ret = -EAGAIN;
  goto ret;
}

(kill() uses SI_USER, but tkill() and tgkill() use SI_TKILL.)

Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
---
 man2/tkill.2 | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/man2/tkill.2 b/man2/tkill.2
index a61ef3182..dce5dd94c 100644
--- a/man2/tkill.2
+++ b/man2/tkill.2
@@ -103,6 +103,18 @@ For the required permissions, see
 .TP
 .B ESRCH
 No process with the specified thread ID (and thread group ID) exists.
+.TP
+.B EAGAIN
+The
+.B RLIMIT_SIGPENDING
+resource limit was reached and
+.I sig
+is a real-time signal.
+.TP
+.B EAGAIN
+Insufficient kernel memory was available and
+.I sig
+is a real-time signal.
 .SH VERSIONS
 .BR tkill ()
 is supported since Linux 2.4.19 / 2.5.4.
-- 
2.11.0.483.g087da7b7c-goog

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