Added text referring to the discussion of async-signal-safe

functions in signal(7).
A few other minor formatting and wording changes.

man2/sigaction.2

@@ -232,20 +232,24 @@ are defined for all signals.
 .RI ( si_signo
 is unused on Linux.)
 The rest of the struct may be a union, so that one should only
-read the fields that are meaningful for the given signal.
+read the fields that are meaningful for the given signal:
+.IP * 2
 POSIX.1b signals and
 .B SIGCHLD
 fill in
 .IR si_pid " and " si_uid .
 .BR
+.IP *
 .B SIGCHLD
 also fills in
 .IR si_status ", " si_utime " and " si_stime .
+.IP *
 .IR si_int " and " si_ptr
 are specified by the sender of the POSIX.1b signal.
-.\" See
-.\" .BR sigqueue (2)
-.\" for more details.
+See
+.BR sigqueue (2)
+for more details.
+.IP *
 .BR SIGILL ,
 .BR SIGFPE ,
 .BR SIGSEGV ,
@@ -257,7 +261,7 @@ with the address of the fault.
 .B SIGPOLL
 fills in
 .IR si_band " and " si_fd .
-
+.PP
 .I si_code
 indicates why this signal was sent.
 It is a value, not a bitmask.
@@ -466,6 +470,11 @@ Attempts to do so are silently ignored.
 See
 .BR sigsetops (3)
 for details on manipulating signal sets.
+.PP
+See
+.BR signal (7)
+for a list of the async-signal-safe functions that can be 
+safely called inside from inside a signal handler.
 .SH BUGS
 In kernels up to and including 2.6.13, specifying
 .B SA_NODEFER