Tell about the downside of safe signals.

p4raw-id: //depot/perl@13588

1 files changed, 10 insertions, 2 deletions

diff --git a/pod/perldelta.pod b/pod/perldelta.pod
index dfb71f9294..15216d4ee8 100644
--- a/pod/perldelta.pod
+++ b/pod/perldelta.pod
@@ -300,11 +300,19 @@ the child process.
 
 =back
 
-=head2 Signals Are Now Safe
+=head2 Safe Signals
 
 Perl used to be fragile in that signals arriving at inopportune moments
 could corrupt Perl's internal state.  Now Perl postpones handling of
-signals until it's safe.
+signals until it's safe (between opcodes).
+
+This change may have surprising side effects because signals no more
+interrupt Perl instantly.  Perl will now first finish whatever it was
+doing, like finishing an internal operation (like sort()) or an
+external operation (like an I/O operation), and only then look at any
+arrived signals (and before starting the next operation).  No more corrupt
+internal state since the current operation is always finished first,
+but the signal may take more time to get heard.
 
 =head2 Unicode Overhaul