[RFC patch 0/3] signals: add rt_tgsigqueueinfo syscall V2

[RFC patch 0/3] signals: add rt_tgsigqueueinfo syscall V2

[Thomas Gleixner]

Changes vs. V1: compat_sys_rt_sigqueueinfo implemented. Thanks Roland !

sys_kill has a counterpart sys_tgkill which allows to send signals to
a particular thread. sys_rt_sigqueueinfo is lacking such a counterpart.

Aside of the asymetry it is a show stopper for migrating applications
from other unix-alike RTOSes.

The following patch series implements rt_tgsigqueueinfo and hooks it
up for x86.

Find below the raw documentation.

Thanks,

	tglx

----

NAME
       rt_tgsigqueueinfo - Send signal information to a signal to a thread

SYNOPSIS
       long sys_rt_tgsigqueueinfo (int tgid, int tid, int sig, siginfo_t *uinfo);

DESCRIPTION

       rt_tgsigqueueinfo sends signal sig information uinfo to the
       thread with the thread ID tid in the thread group tgid.  (By
       contrast, rt_sigqueueinfo(2) can only be used to send a signal
       info to a process (i.e., thread group) as a whole, and the
       signal will be delivered to an arbitrary thread within that
       process.)

RETURN VALUE

       rt_tgsigqueueinfo returns 0 on success; otherwise,
       rt_sigqueueinfo returns one of the errors listed in the
       "Errors" section.

ERRORS
       -EFAULT
              An invalid value for uinfo was specified.

       -EINVAL
	      An invalid TID, TGID or signal was specified.

       -EPERM 
              Permission denied.  For the required permissions,
              see rt_sigqueueinfo(2).

       -ESRCH 
       	      No process with the specified thread ID and thread group
              ID exists.

[RFC patch 1/3] signals: split do_tkill

[Thomas Gleixner]

[-- Attachment #1: signals-split-do-tkill.patch --]
[-- Type: text/plain, Size: 2132 bytes --]

Split out the code from do_tkill to make it reusable by the follow up
patch which implements sys_rt_tgsigqueueinfo

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 kernel/signal.c |   31 ++++++++++++++++++++-----------
 1 file changed, 20 insertions(+), 11 deletions(-)

Index: linux-2.6-tip/kernel/signal.c
===================================================================
--- linux-2.6-tip.orig/kernel/signal.c
+++ linux-2.6-tip/kernel/signal.c
@@ -2212,24 +2212,20 @@ sys_kill(pid_t pid, int sig)
 	return kill_something_info(sig, &info, pid);
 }
 
-static int do_tkill(pid_t tgid, pid_t pid, int sig)
+static int
+do_send_specific(pid_t tgid, pid_t pid, int sig, struct siginfo *info)
 {
-	int error;
-	struct siginfo info;
 	struct task_struct *p;
 	unsigned long flags;
+	int error = -ESRCH;
 
-	error = -ESRCH;
-	info.si_signo = sig;
-	info.si_errno = 0;
-	info.si_code = SI_TKILL;
-	info.si_pid = task_tgid_vnr(current);
-	info.si_uid = current->uid;
+	info->si_pid = task_tgid_vnr(current);
+	info->si_uid = current->uid;
 
 	rcu_read_lock();
 	p = find_task_by_vpid(pid);
 	if (p && (tgid <= 0 || task_tgid_vnr(p) == tgid)) {
-		error = check_kill_permission(sig, &info, p);
+		error = check_kill_permission(sig, info, p);
 		/*
 		 * The null signal is a permissions and process existence
 		 * probe.  No signal is actually delivered.
@@ -2239,7 +2235,7 @@ static int do_tkill(pid_t tgid, pid_t pi
 		 * signal is private anyway.
 		 */
 		if (!error && sig && lock_task_sighand(p, &flags)) {
-			error = specific_send_sig_info(sig, &info, p);
+			error = specific_send_sig_info(sig, info, p);
 			unlock_task_sighand(p, &flags);
 		}
 	}
@@ -2248,6 +2244,19 @@ static int do_tkill(pid_t tgid, pid_t pi
 	return error;
 }
 
+static int do_tkill(pid_t tgid, pid_t pid, int sig)
+{
+	struct siginfo info;
+
+	info.si_signo = sig;
+	info.si_errno = 0;
+	info.si_code = SI_TKILL;
+	info.si_pid = task_tgid_vnr(current);
+	info.si_uid = current->uid;
+
+	return do_send_specific(tgid, pid, sig, &info);
+}
+
 /**
  *  sys_tgkill - send signal to one specific thread
  *  @tgid: the thread group ID of the thread

[RFC patch 2/3] signals: implement sys_rt_tgsigqueueinfo

[Thomas Gleixner]

[-- Attachment #1: signals-implement-rt-tgsigqueueinfo.patch --]
[-- Type: text/plain, Size: 3626 bytes --]

sys_kill has the per thread counterpart sys_tgkill. sigqueueinfo is
missing a thread directed counterpart. Such an interface is important
for migrating applications from other OSes which have the per thread
delivery implemented.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 include/linux/compat.h |    2 ++
 include/linux/signal.h |    2 ++
 kernel/compat.c        |   11 +++++++++++
 kernel/signal.c        |   26 ++++++++++++++++++++++++++
 4 files changed, 41 insertions(+)

Index: linux-2.6-tip/include/linux/compat.h
===================================================================
--- linux-2.6-tip.orig/include/linux/compat.h
+++ linux-2.6-tip/include/linux/compat.h
@@ -209,6 +209,8 @@ int copy_siginfo_from_user32(siginfo_t *
 int copy_siginfo_to_user32(struct compat_siginfo __user *to, siginfo_t *from);
 int get_compat_sigevent(struct sigevent *event,
 		const struct compat_sigevent __user *u_event);
+long compat_sys_rt_tgsigqueueinfo(compat_pid_t tgid, compat_pid_t pid, int sig,
+				  struct compat_siginfo __user *uinfo);
 
 static inline int compat_timeval_compare(struct compat_timeval *lhs,
 					struct compat_timeval *rhs)
Index: linux-2.6-tip/include/linux/signal.h
===================================================================
--- linux-2.6-tip.orig/include/linux/signal.h
+++ linux-2.6-tip/include/linux/signal.h
@@ -235,6 +235,8 @@ static inline int valid_signal(unsigned 
 extern int next_signal(struct sigpending *pending, sigset_t *mask);
 extern int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p);
 extern int __group_send_sig_info(int, struct siginfo *, struct task_struct *);
+extern long do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig,
+				 siginfo_t *info);
 extern long do_sigpending(void __user *, unsigned long);
 extern int sigprocmask(int, sigset_t *, sigset_t *);
 extern int show_unhandled_signals;
Index: linux-2.6-tip/kernel/compat.c
===================================================================
--- linux-2.6-tip.orig/kernel/compat.c
+++ linux-2.6-tip/kernel/compat.c
@@ -836,6 +836,17 @@ compat_sys_rt_sigtimedwait (compat_sigse
 
 }
 
+asmlinkage long
+compat_sys_rt_tgsigqueueinfo(compat_pid_t tgid, compat_pid_t pid, int sig,
+			     struct compat_siginfo __user *uinfo)
+{
+	siginfo_t info;
+
+	if (copy_siginfo_from_user32(&info, uinfo))
+		return -EFAULT;
+	return do_rt_tgsigqueueinfo(tgid, pid, sig, &info);
+}
+
 #ifdef __ARCH_WANT_COMPAT_SYS_TIME
 
 /* compat_time_t is a 32 bit "long" and needs to get converted. */
Index: linux-2.6-tip/kernel/signal.c
===================================================================
--- linux-2.6-tip.orig/kernel/signal.c
+++ linux-2.6-tip/kernel/signal.c
@@ -2307,6 +2307,32 @@ sys_rt_sigqueueinfo(pid_t pid, int sig, 
 	return kill_proc_info(sig, &info, pid);
 }
 
+long do_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, siginfo_t *info)
+{
+	/* This is only valid for single tasks */
+	if (pid <= 0 || tgid <= 0)
+		return -EINVAL;
+
+	/* Not even root can pretend to send signals from the kernel.
+	   Nor can they impersonate a kill(), which adds source info.  */
+	if (info->si_code >= 0)
+		return -EPERM;
+	info->si_signo = sig;
+
+	return do_send_specific(tgid, pid, sig, info);
+}
+
+asmlinkage long
+sys_rt_tgsigqueueinfo(pid_t tgid, pid_t pid, int sig, siginfo_t __user *uinfo)
+{
+	siginfo_t info;
+
+	if (copy_from_user(&info, uinfo, sizeof(siginfo_t)))
+		return -EFAULT;
+
+	return do_rt_tgsigqueueinfo(tgid, pid, sig, &info);
+}
+
 int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
 {
 	struct task_struct *t = current;

[RFC patch 3/3] x86: hookup sys_rt_tgsigqueueinfo

[Thomas Gleixner]

[-- Attachment #1: x86-hookup-rt-tgsigqueueinfo.patch --]
[-- Type: text/plain, Size: 1964 bytes --]

Make the new sys_rt_tgsigqueueinfo available for x86.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/ia32/ia32entry.S          |    1 +
 arch/x86/kernel/syscall_table_32.S |    1 +
 include/asm-x86/unistd_32.h        |    1 +
 include/asm-x86/unistd_64.h        |    2 ++
 4 files changed, 5 insertions(+)

Index: linux-2.6-tip/arch/x86/ia32/ia32entry.S
===================================================================
--- linux-2.6-tip.orig/arch/x86/ia32/ia32entry.S
+++ linux-2.6-tip/arch/x86/ia32/ia32entry.S
@@ -832,4 +832,5 @@ ia32_sys_call_table:
 	.quad sys_dup3			/* 330 */
 	.quad sys_pipe2
 	.quad sys_inotify_init1
+	.quad compat_sys_rt_tgsigqueueinfo
 ia32_syscall_end:
Index: linux-2.6-tip/arch/x86/kernel/syscall_table_32.S
===================================================================
--- linux-2.6-tip.orig/arch/x86/kernel/syscall_table_32.S
+++ linux-2.6-tip/arch/x86/kernel/syscall_table_32.S
@@ -332,3 +332,4 @@ ENTRY(sys_call_table)
 	.long sys_dup3			/* 330 */
 	.long sys_pipe2
 	.long sys_inotify_init1
+	.long sys_rt_tgsigqueueinfo
Index: linux-2.6-tip/include/asm-x86/unistd_32.h
===================================================================
--- linux-2.6-tip.orig/include/asm-x86/unistd_32.h
+++ linux-2.6-tip/include/asm-x86/unistd_32.h
@@ -338,6 +338,7 @@
 #define __NR_dup3		330
 #define __NR_pipe2		331
 #define __NR_inotify_init1	332
+#define __NR_rt_tgsigqueueinfo	333
 
 #ifdef __KERNEL__
 
Index: linux-2.6-tip/include/asm-x86/unistd_64.h
===================================================================
--- linux-2.6-tip.orig/include/asm-x86/unistd_64.h
+++ linux-2.6-tip/include/asm-x86/unistd_64.h
@@ -653,6 +653,8 @@ __SYSCALL(__NR_dup3, sys_dup3)
 __SYSCALL(__NR_pipe2, sys_pipe2)
 #define __NR_inotify_init1			294
 __SYSCALL(__NR_inotify_init1, sys_inotify_init1)
+#define __NR_rt_tgsigqueueinfo			295
+__SYSCALL(__NR_rt_tgsigqueueinfo, sys_rt_tgsigqueueinfo)
 
 
 #ifndef __NO_STUBS

Re: [RFC patch 0/3] signals: add rt_tgsigqueueinfo syscall V2

[Michael Kerrisk]

[CC+=linux-api@vger.kernel.org]

On Wed, Oct 1, 2008 at 12:01 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
> Changes vs. V1: compat_sys_rt_sigqueueinfo implemented. Thanks Roland !
>
> sys_kill has a counterpart sys_tgkill which allows to send signals to
> a particular thread. sys_rt_sigqueueinfo is lacking such a counterpart.
>
> Aside of the asymetry it is a show stopper for migrating applications
> from other unix-alike RTOSes.
>
> The following patch series implements rt_tgsigqueueinfo and hooks it
> up for x86.

This is an excellent candidate for CCing to the new linux-api@vger
(http://thread.gmane.org/gmane.linux.ltp/5658/), since it is an API
change.

> Find below the raw documentation.

Thanks -- I'll work that up into a man page when this gets closer to release.

Cheers,

Michael

> ----
>
> NAME
>       rt_tgsigqueueinfo - Send signal information to a signal to a thread
>
> SYNOPSIS
>       long sys_rt_tgsigqueueinfo (int tgid, int tid, int sig, siginfo_t *uinfo);
>
> DESCRIPTION
>
>       rt_tgsigqueueinfo sends signal sig information uinfo to the
>       thread with the thread ID tid in the thread group tgid.  (By
>       contrast, rt_sigqueueinfo(2) can only be used to send a signal
>       info to a process (i.e., thread group) as a whole, and the
>       signal will be delivered to an arbitrary thread within that
>       process.)
>
> RETURN VALUE
>
>       rt_tgsigqueueinfo returns 0 on success; otherwise,
>       rt_sigqueueinfo returns one of the errors listed in the
>       "Errors" section.
>
> ERRORS
>       -EFAULT
>              An invalid value for uinfo was specified.
>
>       -EINVAL
>              An invalid TID, TGID or signal was specified.
>
>       -EPERM
>              Permission denied.  For the required permissions,
>              see rt_sigqueueinfo(2).
>
>       -ESRCH
>              No process with the specified thread ID and thread group
>              ID exists.
>
>
>



-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
git://git.kernel.org/pub/scm/docs/man-pages/man-pages.git
man-pages online: http://www.kernel.org/doc/man-pages/online_pages.html
Found a bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html

Re: [RFC patch 0/3] signals: add rt_tgsigqueueinfo syscall V2

[Roland McGrath]

Not that I tested it or anything, but this gets a theoretical ACK from me.

Thanks,
Roland

Re: [RFC patch 0/3] signals: add rt_tgsigqueueinfo syscall V2

[Ingo Molnar]

* Roland McGrath <roland@redhat.com> wrote:

> Not that I tested it or anything, but this gets a theoretical ACK from me.

btw., you can send a Reviewed-by: Roland McGrath <roland@redhat.com> 
line in that case - i'm sure Thomas will appreciate it.

	Ingo

Re: [RFC patch 0/3] signals: add rt_tgsigqueueinfo syscall V2

[Thomas Gleixner]

On Wed, 1 Oct 2008, Michael Kerrisk wrote:
> [CC+=linux-api@vger.kernel.org]
> 
> On Wed, Oct 1, 2008 at 12:01 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
> > Changes vs. V1: compat_sys_rt_sigqueueinfo implemented. Thanks Roland !
> >
> > sys_kill has a counterpart sys_tgkill which allows to send signals to
> > a particular thread. sys_rt_sigqueueinfo is lacking such a counterpart.
> >
> > Aside of the asymetry it is a show stopper for migrating applications
> > from other unix-alike RTOSes.
> >
> > The following patch series implements rt_tgsigqueueinfo and hooks it
> > up for x86.
> 
> This is an excellent candidate for CCing to the new linux-api@vger
> (http://thread.gmane.org/gmane.linux.ltp/5658/), since it is an API
> change.

Oops, yes forgot about that.
 
> > Find below the raw documentation.
> 
> Thanks -- I'll work that up into a man page when this gets closer to release.

I'll send out test code later this week - once I get a breather from
bugs and regressions again.

Thanks,

	tglx

Re: [RFC patch 0/3] signals: add rt_tgsigqueueinfo syscall V2

[Michael Kerrisk]

Hi Thomas,

On Thu, Oct 2, 2008 at 10:57 AM, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Wed, 1 Oct 2008, Michael Kerrisk wrote:
>> [CC+=linux-api@vger.kernel.org]
>>
>> On Wed, Oct 1, 2008 at 12:01 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
>> > Changes vs. V1: compat_sys_rt_sigqueueinfo implemented. Thanks Roland !
>> >
>> > sys_kill has a counterpart sys_tgkill which allows to send signals to
>> > a particular thread. sys_rt_sigqueueinfo is lacking such a counterpart.
>> >
>> > Aside of the asymetry it is a show stopper for migrating applications
>> > from other unix-alike RTOSes.
>> >
>> > The following patch series implements rt_tgsigqueueinfo and hooks it
>> > up for x86.
>>
>> This is an excellent candidate for CCing to the new linux-api@vger
>> (http://thread.gmane.org/gmane.linux.ltp/5658/), since it is an API
>> change.
>
> Oops, yes forgot about that.
>
>> > Find below the raw documentation.
>>
>> Thanks -- I'll work that up into a man page when this gets closer to release.
>
> I'll send out test code later this week - once I get a breather from
> bugs and regressions again.

So I've done some testing of this interface (I've substantially
revised the test programs that I sent yesterday, and have included
them again below).

Two potential issues that I see, both of which relate to
inconsistencies with rt_sigqueueinfo():

1) With rt_siqueueinfo(), we can get the PID (TGID) of the sender,
which enables the receiver of the signal to know who the sender was,
and perhaps use that information to (for example) send a signal in the
other direction.

With rt_tgsigqueueinfo(), we don't quite have that ability: all that
the receiver gets is the TGID of the sender, not the TID.  This means
that we can't (for example) send a signal back to the precise thread
that signaled us. I'm not sure if this matters or not (but perhaps it
might when sender and receiver are in the same process?).  I'm also
not sure whether we want to do anything about this (i.e., extending
siginfo_t to include a si_tid field), but I wanted to point out this
assymetry w.r.t. to rt_sigqueueinfo(), in case you had not considered
it.

2) With rt_sigqueueinfo(), we can specify the si_pid and and si_uid
fields that should be sent to the receiver.  This is not possible with
rt_tgsigqueueinfo(), which always supplied the caller';s PID and UID
in the si_pid and si_uid fields sent to the receiver.  See the
following, created using my test programs below (the 111 & 222
arguments to t_*sigqueueinfo set the si_pid and si_uid fields in the
siginfo_t given to the *sigqueueinfo() syscall):

$ ./multithread_sig_receiver 0
Main: TGID = 11711; TID = 11711
Main: blocked signals
Thread 1: PID = 11711; TID = 11712
Thread 1: about to wait for signals
Thread 0: about to wait for signals
                        $ ./t_rt_sigqueueinfo 11711 44 1 -1 111 222
                        My PID is 11714
Thread 0: got signal: si_signo=44 si_code=-1 si_pid=111 si_uid=222
si_value.sival_int=1
                        $ ./t_rt_tgsigqueueinfo 11711 11712 44 1 -1 111 222
                        My PID is 11715
Thread 1: got signal: si_signo=44 si_code=-1 si_pid=11715 si_uid=1000
si_value.sival_int=1

The problem is the different code paths taken by
rt_tgsigqueueinfo()/tgkill() versus rt_sigqueueinfo():

sys_rt_sigqueueinfo()  sys_tgkill()                sys_rt_sigqueueinfo()
        |                   |                              |
        v                   v                              v
do_rt_sigqueueinfo()   do_tkill()                  kill_proc_info()
        |                   |                              |
        |                   v                              v
        +------------> do_send_specific()          kill_pid_info()
                            |                              |
                            v                              v
                       specific_send_sig_info()    group_send_sig_info()
                            |                              |
                            |                              v
                            |                      __group_send_sig_info()
                            |                              |
                            |                              v
                            +--------------------> send_signal()

And in do_send_specifc() there are the lines:

        info->si_pid = task_tgid_vnr(current);
        info->si_uid = current->uid;

I suspect this should be fixed to be consistent with sigqueueinfo().

Cheers,

Michael

=====

/*#* multithread_sig_receiver.c

   Copyright 2008, Linux Foundation;
   written by Michael Kerrisk <mtk.manpages@gmail.com>
*/
#define _GNU_SOURCE
#include <sys/syscall.h>
#include <ctype.h>
#include <unistd.h>
#include <signal.h>
#include <pthread.h>
#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

#define errExit(msg)    do { perror(msg); exit(EXIT_FAILURE); \
                        } while (0)

#define errExitEN(en, msg) \
                        do { errno = en; perror(msg); \
                             exit(EXIT_FAILURE); } while (0)

static sigset_t test_sigs;

struct thread_arg {
    int   thread_num;
    char *argv_string;
};

static pid_t
gettid(void)
{
    return syscall(SYS_gettid);
}

#if 0
static void
handler(int sig, siginfo_t *si, void *uc)
{
    printf("PID = %ld; TID = %ld; caught signal %d: \n",
            (long) getpid(), (long) gettid(), sig);
    printf("%p\n", si);
    printf("si_signo=%d ", si->si_signo);
    printf("si_code=%d ", si->si_code);
    printf("si_pid=%ld ", (long) si->si_pid);
    printf("si_uid=%ld ", (long) si->si_uid);
    printf("si_value.sival_int=%d\n", si->si_value.sival_int);
}
#endif

static void
wait_for_signals(int tnum)
{
    siginfo_t si;

    printf("Thread %d: about to wait for signals\n", tnum);

    for (;;) {
        if (sigwaitinfo(&test_sigs, &si) == -1)
            errExit("sigwaitinfo");
        printf("Thread %d: got signal: ", tnum);
        printf("si_signo=%d ", si.si_signo);
        printf("si_code=%d ", si.si_code);
        printf("si_pid=%ld ", (long) si.si_pid);
        printf("si_uid=%ld ", (long) si.si_uid);
        printf("si_value.sival_int=%d\n", si.si_value.sival_int);
    }
} /* wait_for_signals */


static void *
threadFunc(void *arg)
{
    struct thread_arg *ta = (struct thread_arg *) arg;
    int nsecs;

    printf("Thread %d: PID = %ld; TID = %ld\n", ta->thread_num,
            (long) getpid(), (long) gettid());

    nsecs = atoi(ta->argv_string);

    if (nsecs > 0) {
        printf("Thread %d: sleeping\n", ta->thread_num);
        sleep(nsecs);
        printf("Thread %d: finished sleeping\n", ta->thread_num);
    }

    wait_for_signals(ta->thread_num);
    return NULL;        /* NOTREACHED */
} /* threadFunc */


#define MAX_ARGS 1000

int
main(int argc, char *argv[])
{
    pthread_t t;
    int s, j;
//    struct sigaction sa;
    struct thread_arg ta[MAX_ARGS];
    sigset_t new;

    if (argc < 2) {
        fprintf(stderr, "Usage: %s <nsecs>...\n", argv[0]);
        fprintf(stderr, "Each <nsecs> argument causes a separate "
                "thread to be created;\n");
        fprintf(stderr, "The thread sleeps <nsecs> seconds before "
                "accepting signals with sigwaitinfo()\n");

        fprintf(stderr, "\n");
        exit(EXIT_SUCCESS);
    }

    if (argc > MAX_ARGS) {
        fprintf(stderr, "Too many arguments\n");
        exit(EXIT_SUCCESS);
    }

    sigemptyset(&test_sigs);
    for (s = 1; s < NSIG; s++)
        if (s != SIGINT && s != SIGQUIT && s != SIGTERM)
            sigaddset(&test_sigs, s);

    sigemptyset(&new);
    if (sigprocmask(SIG_SETMASK, &new, NULL) == -1)
        errExit("sigprocmask");

#if 0
    for (s = 1; s < NSIG; s++) {
        if (sigismember(&test_sigs, s)) {
            sa.sa_flags = SA_SIGINFO;
            sa.sa_sigaction = handler;
            sigemptyset(&sa.sa_mask);
            if (sigaction(s, &sa, NULL) == -1 && errno != EINVAL)
                errExit("sigaction");
        }
    }
    printf("Established handler for signals\n");
#endif

    printf("Main: TGID = %ld; TID = %ld\n",
            (long) getpid(), (long) gettid());

    s = pthread_sigmask(SIG_SETMASK, &test_sigs, NULL);
    if (s != 0)
        errExit("pthread_sigmask");
    printf("Main: blocked signals\n");

    for (j = 0; j + 1 < argc; j++) {
        ta[j].thread_num = j + 1;
        ta[j].argv_string = argv[j + 1];

        s = pthread_create(&t, NULL, threadFunc, &ta[j]);
        if (s != 0)
            errExitEN(s, "pthread_create");
    }

    wait_for_signals(0);
} /* main */

=====

/*#* t_rt_tgsigqueueinfo.c

   Copyright 2008, Linux Foundation;
   written by Michael Kerrisk <mtk.manpages@gmail.com>
*/
#define _GNU_SOURCE
#include <unistd.h>
#include <sys/syscall.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <signal.h>
#include <sys/types.h>

#define errExit(msg)    do { perror(msg); exit(EXIT_FAILURE); \
                        } while (0)

#if defined(__i386__)
#define SYS_rt_tgsigqueueinfo 333
#endif

static int
rt_tgsigqueueinfo(pid_t tgid, pid_t tid, int sig, siginfo_t *si)
{
    return syscall(SYS_rt_tgsigqueueinfo, tgid, tid, sig, si);
}


int
main(int argc, char *argv[])
{
    pid_t tgid, tid;
    siginfo_t si;
    int sig, val;

    if (argc < 5) {
        fprintf(stderr, "Usage: %s <tgid> <tid> <sig> <val> "
                "[<si_code> [<si_pid [<si_uid>]]]\n", argv[0]);
        exit(EXIT_SUCCESS);
    }

    printf("My PID is %ld\n", (long) getpid());

    tgid = atoi(argv[1]);
    tid = atoi(argv[2]);
    sig = atoi(argv[3]);
    val = atoi(argv[4]);

    si.si_signo = sig + 1;
    si.si_code = (argc > 5) ? atoi(argv[5]) : SI_QUEUE;
    si.si_pid = (argc > 6) ? atoi(argv[6]) : getpid();
    si.si_uid = (argc > 7) ? atoi(argv[7]) : getuid();
    si.si_value.sival_int = val;

    /*
    printf("Sending: si.si_signo = %d, si.si_code = %d, "
            "si.si_pid = %ld, si.si_uid = %ld\n",
            si.si_signo, si.si_code, (long) si.si_pid, (long) si.si_uid);
    */
    if (rt_tgsigqueueinfo(tgid, tid, sig, &si) == -1)
        errExit("rt_tgsigqueueinfo");

    exit(EXIT_SUCCESS);
} /* main */

=====

/*#* t_rt_sigqueueinfo.c

   Copyright 2008, Linux Foundation;
   written by Michael Kerrisk <mtk.manpages@gmail.com>
*/
#define _GNU_SOURCE
#include <unistd.h>
#include <sys/syscall.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <signal.h>
#include <sys/types.h>

#define errExit(msg)    do { perror(msg); exit(EXIT_FAILURE); \
                        } while (0)

static int
rt_sigqueueinfo(pid_t tgid, int sig, siginfo_t *si)
{
    return syscall(SYS_rt_sigqueueinfo, tgid, sig, si);
}


int
main(int argc, char *argv[])
{
    pid_t tgid;
    siginfo_t si;
    int sig, val;

    if (argc < 4) {
        fprintf(stderr, "Usage: %s <tgid> <sig> <val> "
                "[<si_code> [<si_pid [<si_uid>]]]\n", argv[0]);
        exit(EXIT_SUCCESS);
    }

    printf("My PID is %ld\n", (long) getpid());

    tgid = atoi(argv[1]);
    sig = atoi(argv[2]);
    val = atoi(argv[3]);

    si.si_signo = sig + 1;
    si.si_code = (argc > 4) ? atoi(argv[4]) : SI_QUEUE;
    si.si_pid = (argc > 5) ? atoi(argv[5]) : getpid();
    si.si_uid = (argc > 6) ? atoi(argv[6]) : getuid();
    si.si_value.sival_int = val;

    /*
    printf("Sending: si.si_signo = %d, si.si_code = %d, "
            "si.si_pid = %ld, si.si_uid = %ld\n",
            si.si_signo, si.si_code, (long) si.si_pid, (long) si.si_uid);
    */
    if (rt_sigqueueinfo(tgid, sig, &si) == -1)
        errExit("rt_sigqueueinfo");

    exit(EXIT_SUCCESS);
} /* main */

=====