diff options
Diffstat (limited to 'hurd/hurdioctl.c')
-rw-r--r-- | hurd/hurdioctl.c | 66 |
1 files changed, 47 insertions, 19 deletions
diff --git a/hurd/hurdioctl.c b/hurd/hurdioctl.c index 8482571..073c15e 100644 --- a/hurd/hurdioctl.c +++ b/hurd/hurdioctl.c @@ -1,5 +1,5 @@ /* ioctl commands which must be done in the C library. - Copyright (C) 1994, 1995, 1996, 1997 Free Software Foundation, Inc. + Copyright (C) 1994, 1995, 1996, 1997, 1999 Free Software Foundation, Inc. This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or @@ -132,13 +132,39 @@ _HURD_HANDLE_IOCTLS (fioclex, FIOCLEX, FIONCLEX); #include <hurd/term.h> #include <hurd/tioctl.h> -static void -rectty_dtable (mach_port_t cttyid) +/* Install a new CTTYID port, atomically updating the dtable appropriately. + This consumes the send right passed in. */ + +void +_hurd_locked_install_cttyid (mach_port_t cttyid) { + mach_port_t old; + struct hurd_port *const port = &_hurd_ports[INIT_PORT_CTTYID]; + struct hurd_userlink ulink; int i; - HURD_CRITICAL_BEGIN; - __mutex_lock (&_hurd_dtable_lock); + /* Install the new cttyid port, and preserve it with a ulink. + We unroll the _hurd_port_set + _hurd_port_get here so that + there is no window where the cell is unlocked and CTTYID could + be changed by another thread. (We also delay the deallocation + of the old port until the end, to minimize the duration of the + critical section.) + + It is important that changing the cttyid port is only ever done by + holding the dtable lock continuously while updating the port cell and + re-ctty'ing the dtable; dtable.c assumes we do this. Otherwise, the + pgrp-change notification code in dtable.c has to worry about racing + against us here in odd situations. The one exception to this is + setsid, which holds the dtable lock while changing the pgrp and + clearing the cttyid port, and then unlocks the dtable lock to allow + + + */ + + __spin_lock (&port->lock); + old = _hurd_userlink_clear (&port->users) ? port->port : MACH_PORT_NULL; + port->port = cttyid; + cttyid = _hurd_port_locked_get (port, &ulink); for (i = 0; i < _hurd_dtablesize; ++i) { @@ -178,6 +204,18 @@ rectty_dtable (mach_port_t cttyid) } __mutex_unlock (&_hurd_dtable_lock); + + if (old != MACH_PORT_NULL) + __mach_port_deallocate (__mach_task_self (), old); + _hurd_port_free (port, &ulink, cttyid); +} + +static void +install_ctty (mach_port_t cttyid) +{ + HURD_CRITICAL_BEGIN; + __mutex_lock (&_hurd_dtable_lock); + _hurd_locked_install_cttyid (cttyid); HURD_CRITICAL_END; } @@ -199,10 +237,7 @@ _hurd_setcttyid (mach_port_t cttyid) } /* Install the port, consuming the reference we just created. */ - _hurd_port_set (&_hurd_ports[INIT_PORT_CTTYID], cttyid); - - /* Reset all the ctty ports in all the descriptors. */ - __USEPORT (CTTYID, (rectty_dtable (cttyid), 0)); + install_ctty (cttyid); return 0; } @@ -233,10 +268,7 @@ tiocsctty (int fd, return __hurd_fail (err); /* Make it our own. */ - _hurd_port_set (&_hurd_ports[INIT_PORT_CTTYID], cttyid); - - /* Reset all the ctty ports in all the descriptors. */ - __USEPORT (CTTYID, (rectty_dtable (cttyid), 0)); + install_ctty (cttyid); return 0; } @@ -262,12 +294,8 @@ tiocnotty (int fd, if (err) return __hurd_fail (err); - /* Clear our cttyid port cell. */ - _hurd_port_set (&_hurd_ports[INIT_PORT_CTTYID], MACH_PORT_NULL); - - /* Reset all the ctty ports in all the descriptors. */ - - __USEPORT (CTTYID, (rectty_dtable (MACH_PORT_NULL), 0)); + /* Clear our cttyid port. */ + install_ctty (MACH_PORT_NULL); return 0; } |