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Provide consistent locking around getc() in ttread(). This is necessary 

to prevent crashes in MPSAFE tty drivers like ucom.
This commit is contained in:
mlelstv 2012-09-30 11:49:44 +00:00
parent 219dae9ba5
commit cfb7ebba73
1 changed files with 5 additions and 8 deletions
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13
sys/kern/tty.c
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@ -1,4 +1,4 @@
/* $NetBSD: tty.c,v 1.253 2012/08/17 16:21:19 christos Exp $ */
/* $NetBSD: tty.c,v 1.254 2012/09/30 11:49:44 mlelstv Exp $ */
/*-
* Copyright (c) 2008 The NetBSD Foundation, Inc.
@ -63,7 +63,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: tty.c,v 1.253 2012/08/17 16:21:19 christos Exp $");
__KERNEL_RCSID(0, "$NetBSD: tty.c,v 1.254 2012/09/30 11:49:44 mlelstv Exp $");
#include <sys/param.h>
#include <sys/systm.h>
@ -1928,7 +1928,6 @@ ttread(struct tty *tp, struct uio *uio, int flag)
goto loop;
}
read:
mutex_spin_exit(&tty_lock);
/*
* Input present, check for input mapping and processing.
@ -1940,16 +1939,14 @@ ttread(struct tty *tp, struct uio *uio, int flag)
*/
if (CCEQ(cc[VDSUSP], c) &&
ISSET(lflag, IEXTEN|ISIG) == (IEXTEN|ISIG)) {
mutex_spin_enter(&tty_lock);
ttysig(tp, TTYSIG_PG1, SIGTSTP);
if (first) {
error = ttypause(tp, hz);
mutex_spin_exit(&tty_lock);
if (error)
break;
goto loop;
} else
mutex_spin_exit(&tty_lock);
goto loop;
}
break;
}
/*
@ -1973,11 +1970,11 @@ ttread(struct tty *tp, struct uio *uio, int flag)
break;
first = 0;
}
/*
* Look to unblock output now that (presumably)
* the input queue has gone down.
*/
mutex_spin_enter(&tty_lock);
if (ISSET(tp->t_state, TS_TBLOCK) && tp->t_rawq.c_cc < TTYHOG / 5) {
if (ISSET(tp->t_iflag, IXOFF) &&
cc[VSTART] != _POSIX_VDISABLE &&