2.5.75

 kernel

diff -Nru a/kernel/signal.c b/kernel/signal.c
--- a/kernel/signal.c   Thu Jul 10 13:16:27 2003
+++ b/kernel/signal.c   Thu Jul 10 13:16:27 2003
@@ -579,8 +579,8 @@
 /*
  * Bad permissions for sending the signal
  */
-static inline int check_kill_permission(int sig, struct siginfo *info,
-               struct task_struct *t)
+static int check_kill_permission(int sig, struct siginfo *info,
+             struct task_struct *t)
 {
    int error = -EINVAL;
    if (sig < 0 || sig > _NSIG)
@@ -797,10 +797,11 @@
    int ret;
 
    spin_lock_irqsave(&t->sighand->siglock, flags);
-   if (t->sighand->action[sig-1].sa.sa_handler == SIG_IGN)
+   if (sigismember(&t->blocked, sig) || t->sighand->action[sig-1].sa.sa_handler == SIG_IGN) {
       t->sighand->action[sig-1].sa.sa_handler = SIG_DFL;
-   sigdelset(&t->blocked, sig);
-   recalc_sigpending_tsk(t);
+      sigdelset(&t->blocked, sig);
+      recalc_sigpending_tsk(t);
+   }
    ret = specific_send_sig_info(sig, info, t);
    spin_unlock_irqrestore(&t->sighand->siglock, flags);
 
@@ -2081,12 +2082,58 @@
    info.si_signo = sig;
    info.si_errno = 0;
    info.si_code = SI_USER;
-   info.si_pid = current->pid;
+   info.si_pid = current->tgid;
    info.si_uid = current->uid;
 
    return kill_something_info(sig, &info, pid);
 }
 
+/**
+ *  sys_tkill - send signal to one specific thread
+ *  @tgid: the thread group ID of the thread
+ *  @pid: the PID of the thread
+ *  @sig: signal to be sent
+ *
+ *  This syscall also checks the tgid and returns -ESRCH even if the PID
+ *  exists but it's not belonging to the target process anymore. This
+ *  method solves the problem of threads exiting and PIDs getting reused.
+ */
+asmlinkage long sys_tgkill(int tgid, int pid, int sig)
+{
+   struct siginfo info;
+   int error;
+   struct task_struct *p;
+
+   /* This is only valid for single tasks */
+   if (pid <= 0 || tgid <= 0)
+      return -EINVAL;
+
+   info.si_signo = sig;
+   info.si_errno = 0;
+   info.si_code = SI_TKILL;
+   info.si_pid = current->tgid;
+   info.si_uid = current->uid;
+
+   read_lock(&tasklist_lock);
+   p = find_task_by_pid(pid);
+   error = -ESRCH;
+   if (p && (p->tgid == tgid)) {
+      error = check_kill_permission(sig, &info, p);
+      /*
+       * The null signal is a permissions and process existence
+       * probe.  No signal is actually delivered.
+       */
+      if (!error && sig && p->sighand) {
+         spin_lock_irq(&p->sighand->siglock);
+         handle_stop_signal(sig, p);
+         error = specific_send_sig_info(sig, &info, p);
+         spin_unlock_irq(&p->sighand->siglock);
+      }
+   }
+   read_unlock(&tasklist_lock);
+   return error;
+}
+
 /*
  *  Send a signal to only one task, even if it's a CLONE_THREAD task.
  */
@@ -2104,7 +2151,7 @@
    info.si_signo = sig;
    info.si_errno = 0;
    info.si_code = SI_TKILL;
-   info.si_pid = current->pid;
+   info.si_pid = current->tgid;
    info.si_uid = current->uid;
 
    read_lock(&tasklist_lock);