121276 - use sigthreadmask instead of sigprocmask in libldap/os-ip.c

Status: RESOLVED FIXED

Description

[Mark Smith (:mcs)]

[e-mail] said:

   I'm doing development of multi-threaded application for AIX 4.3.3
   platform. While browing through the C-SDK sources (both 0.9.4
   and 0.9.7) I found out <sigprocmask> at <libldap/os-ip.c> in
   <nsldapi_connection_to_host>. To me, the call is potentially
   dangerous and <sigthreadmask> has to be used instead. Am I
   right or am I missing something?

I am not sure if this is a bug or not.  According to the Solaris 8 man page:

	"In a multithreaded program, the call to sigpromask()
	impacts only the calling thread's signal mask and is there-
  	fore identical to a call to thr_sigsetmask(3THR).

What does the AIX 4.3.3 man page say?

Comment 1

[Michael Hein]

According to the man page it would appear that this call is threadsafe.

sigprocmask - examine and change blocked signals 

SYNOPSIS

#include <signal.h>

int sigprocmask (how, set, oset) 
int how; 
sigset_t *set, *oset;

DESCRIPTION

The sigprocmask function is used to examine or change (or both) the calling 
process's signal mask. If the value of set is not NULL, it points to a set of 
signals
to be used to change the currently blocked set.

The value of how indicates the manner in which the set is changed, and consists 
of one of the following values, as defined in the header <signal.h>:

SIG_BLOCK
       The resulting set shall be the union of the current set and the signal 
set pointed to by set.
SIG_UNBLOCK
       The resulting set shall be the intersection of the current set and the 
complement of the signal set pointed to by set.
SIG_SETMASK
       The resulting set shall be the signal set pointed to by the argument set. 

If oset is not NULL, the previous mask is stored in the space pointed to by 
oset. If the value of set is NULL, the value of how is not significant and the
process's signal mask is unchanged by this function call; thus, the call can be 
used to inquire about currently blocked signals.

If there are any pending unblocked signals after the call to sigprocmask, at 
least one of those signals is delivered before sigprocmask returns.

It is impossible to block the SIGKILL and SIGSTOP signals; this is enforced by 
the system without causing an error to be indicated.

If any of the SIGFPE, SIGLL or SIGSEGV signals are generated while they are 
blocked, the result is undefined, unless the signal was generated by a call to
the kill function.

If sigprocmask fails, the process's signal mask is not changed by this function 
call.

On sucessful completion, a value of zero is returned. Otherwise, a value of -1 
is returned and errno is set to indicate the error.

If the following condition occurs, sigprocmask returns -1 and sets errno to the 
corresponding value:

[EINVAL]
       The value of how is not equal to one of the defined values. 

THREAD-SAFETY NOTES

sigprocmask: Thread-safe.

SEE ALSO

sigaction(2), sigemptyset(2), sigpending(2), sigset(2), sigsuspend(2) 

Comment 2

[Mark Smith (:mcs)]

On most operatinjg systems, sigprocmask() is MT safe and it only affects the
calling thread. But the AIX 4.3 and AIX5 sigprocmask() man pages includes this note:

  Note: The sigprocmask, sigsetmask, and sigblock subroutines must
  not be used in a multi-threaded application. The sigthreadmask
  subroutine must be used instead.

I have a patch.

Comment 3

[Mark Smith (:mcs)]

Created attachment 79801 [details] [diff] [review]
proposed fix

Comment 4

[Mark Smith (:mcs)]

Fixed on the trunk:

mozilla/directory/c-sdk/ldap/include/portable.h
  new revision: 5.2; previous revision: 5.1
mozilla/directory/c-sdk/ldap/libraries/libldap/charray.c
  new revision: 5.1; previous revision: 5.0
mozilla/directory/c-sdk/ldap/libraries/libldap/os-ip.c
  new revision: 5.3; previous revision: 5.2
    Fix bug # 99068 - Can't compile on NetBSD.
    Fix bug # 121276 - use sigthreadmask instead of sigprocmask (AIX).
    Fix bug # 81584 - strtok use and STRTOK on Linux.
        The charray() code now uses strtok_r() if available.
        strtok_r() is now used everywhere on Linux if available.