Don't assume that p_session hasn't changed out from under us after unlocking
the process and session. Instead, cache a true reference to the session when we do the hold and release our reference on that session. This avoids the need for the proc lock when dropping the reference.
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@ -161,22 +161,23 @@ void
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tprintf(struct proc *p, int pri, const char *fmt, ...)
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{
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struct tty *tp = NULL;
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int flags = 0, shld = 0;
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int flags = 0;
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va_list ap;
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struct putchar_arg pca;
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int retval;
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struct session *sess = NULL;
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if (pri != -1)
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flags |= TOLOG;
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if (p != NULL) {
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PROC_LOCK(p);
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if (p->p_flag & P_CONTROLT && p->p_session->s_ttyvp) {
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SESS_LOCK(p->p_session);
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SESSHOLD(p->p_session);
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tp = p->p_session->s_ttyp;
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SESS_UNLOCK(p->p_session);
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sess = p->p_session;
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SESS_LOCK(sess);
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PROC_UNLOCK(p);
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shld++;
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SESSHOLD(sess);
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tp = sess->s_ttyp;
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SESS_UNLOCK(sess);
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if (ttycheckoutq(tp, 0))
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flags |= TOTTY;
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else
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@ -190,12 +191,10 @@ tprintf(struct proc *p, int pri, const char *fmt, ...)
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va_start(ap, fmt);
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retval = kvprintf(fmt, putchar, &pca, 10, ap);
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va_end(ap);
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if (shld) {
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PROC_LOCK(p);
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SESS_LOCK(p->p_session);
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SESSRELE(p->p_session);
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SESS_UNLOCK(p->p_session);
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PROC_UNLOCK(p);
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if (sess != NULL) {
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SESS_LOCK(sess);
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SESSRELE(sess);
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SESS_UNLOCK(sess);
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}
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msgbuftrigger = 1;
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}
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