On Tue, 3 Jun 2003, Linus Torvalds wrote:
> > are you suggesting to extend sys_tgkill() functionality to also detect -1
> > for the PID, and do a process-signal send?
>
> I don't care much, but that zero special case is definitely not a good
> idea.
>
> You might make the thing acceptable to me by just removing the "zero means
> everythign", and replacing that logic with
>
> if (!tgid)
> tgid = current->tgid;
>
> which is similar to how we handle zeroes in some other places. In other
> words, a zero is not a "wildcard", it means "_this_ thread group".
i did it this way mostly because i wanted to avoid duplicating code, and
wanted to 'fold' tkill into the new variant.
in the attached patch sys_tgkill(tgid,pid,sig) means only that, nothing
more: send the signal to the thread specified by (tgid,pid) - return
-ESRCH if it does not exist in that combination.
Ingo
--- linux/include/asm-i386/unistd.h.orig
+++ linux/include/asm-i386/unistd.h
@@ -273,6 +273,7 @@
#define __NR_clock_gettime (__NR_timer_create+6)
#define __NR_clock_getres (__NR_timer_create+7)
#define __NR_clock_nanosleep (__NR_timer_create+8)
+#define __NR_tgkill 268
#define NR_syscalls 268
--- linux/arch/i386/kernel/entry.S.orig
+++ linux/arch/i386/kernel/entry.S
@@ -874,6 +874,7 @@ ENTRY(sys_call_table)
.long sys_clock_gettime /* 265 */
.long sys_clock_getres
.long sys_clock_nanosleep
+ .long sys_tgkill
nr_syscalls=(.-sys_call_table)/4
--- linux/kernel/signal.c.orig
+++ linux/kernel/signal.c
@@ -570,7 +570,7 @@ static int rm_from_queue(unsigned long m
/*
* Bad permissions for sending the signal
*/
-static inline int check_kill_permission(int sig, struct siginfo *info,
+static int check_kill_permission(int sig, struct siginfo *info,
struct task_struct *t)
{
int error = -EINVAL;
@@ -1930,6 +1930,52 @@ sys_kill(int pid, int sig)
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->pid;
+ 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.
*/
-
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This archive was generated by hypermail 2b29 : Sat Jun 07 2003 - 22:00:20 EST