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Don't assume that p_session hasn't changed out from under us after unlocking

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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.
This commit is contained in:
John Baldwin 2003-04-17 22:30:43 +00:00
parent f385f7156a
commit b5a2bad175
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=113634
1 changed files with 11 additions and 12 deletions
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23
sys/kern/subr_prf.c
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@ -161,22 +161,23 @@ void
tprintf(struct proc *p, int pri, const char *fmt, ...)
{
struct tty *tp = NULL;
int flags = 0, shld = 0;
int flags = 0;
va_list ap;
struct putchar_arg pca;
int retval;
struct session *sess = NULL;
if (pri != -1)
flags |= TOLOG;
if (p != NULL) {
PROC_LOCK(p);
if (p->p_flag & P_CONTROLT && p->p_session->s_ttyvp) {
SESS_LOCK(p->p_session);
SESSHOLD(p->p_session);
tp = p->p_session->s_ttyp;
SESS_UNLOCK(p->p_session);
sess = p->p_session;
SESS_LOCK(sess);
PROC_UNLOCK(p);
shld++;
SESSHOLD(sess);
tp = sess->s_ttyp;
SESS_UNLOCK(sess);
if (ttycheckoutq(tp, 0))
flags |= TOTTY;
else
@ -190,12 +191,10 @@ tprintf(struct proc *p, int pri, const char *fmt, ...)
va_start(ap, fmt);
retval = kvprintf(fmt, putchar, &pca, 10, ap);
va_end(ap);
if (shld) {
PROC_LOCK(p);
SESS_LOCK(p->p_session);
SESSRELE(p->p_session);
SESS_UNLOCK(p->p_session);
PROC_UNLOCK(p);
if (sess != NULL) {
SESS_LOCK(sess);
SESSRELE(sess);
SESS_UNLOCK(sess);
}
msgbuftrigger = 1;
}