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PR 48587 Newunit allocator 

Currently GFortran newer reuses unit numbers allocated with NEWUNIT=,
instead having a simple counter that is decremented each time such a
unit is opened.  For a long running program which repeatedly opens
files with NEWUNIT= and closes them, the counter can wrap around and
cause an abort.  This patch replaces the counter with an allocator
that keeps track of which units numbers are allocated, and can reuse
them once they have been deallocated.  Since operating systems tend to
limit the number of simultaneous open files for a process to a
relatively modest number, a relatively simple approach with a linear
scan through an array suffices.  Though as a small optimization there
is a low water indicator keeping track of the index for which all unit
numbers below are already allocated.  This linear scan also ensures
that we always allocate the smallest available unit number.

2016-10-15  Janne Blomqvist  <jb@gcc.gnu.org>

        PR libfortran/48587
        * io/io.h (get_unique_unit_number): Remove prototype.
        (newunit_alloc): New prototype.
        * io/open.c (st_open): Call newunit_alloc.
        * io/unit.c (newunits,newunit_size,newunit_lwi): New static
        variables.
        (GFC_FIRST_NEWUNIT): Rename to NEWUNIT_START.
        (next_available_newunit): Remove variable.
        (get_unit): Call newunit_alloc, don't try to create negative
        external unit.
        (close_unit_1): Call newunit_free.
        (close_units): Free newunits array.
        (get_unique_number): Remove function.
        (newunit_alloc): New function.
        (newunit_free): New function.
        * io/transfer.c (data_transfer_init): Check for invalid unit
        number.

testsuite ChangeLog:

2016-10-15  Janne Blomqvist  <jb@gcc.gnu.org>

        PR libfortran/48587
        * gfortran.dg/negative_unit2.f90: New testcase.

From-SVN: r241199
This commit is contained in:
Janne Blomqvist 2016-10-15 16:14:15 +03:00
parent 64190f049a
commit c04d4ede17
6 changed files with 123 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
gcc/testsuite/ChangeLog
View File

@ -1,3 +1,8 @@
2016-10-15 Janne Blomqvist <jb@gcc.gnu.org>
PR libfortran/48587
* gfortran.dg/negative_unit2.f90: New test.
2016-10-14 Jakub Jelinek <jakub@redhat.com>
PR middle-end/77959

20
libgfortran/ChangeLog
View File

@ -1,3 +1,23 @@
2016-10-15 Janne Blomqvist <jb@gcc.gnu.org>
PR libfortran/48587
* io/io.h (get_unique_unit_number): Remove prototype.
(newunit_alloc): New prototype.
* io/open.c (st_open): Call newunit_alloc.
* io/unit.c (newunits,newunit_size,newunit_lwi): New static
variables.
(GFC_FIRST_NEWUNIT): Rename to NEWUNIT_START.
(next_available_newunit): Remove variable.
(get_unit): Call newunit_alloc, don't try to create negative
external unit.
(close_unit_1): Call newunit_free.
(close_units): Free newunits array.
(get_unique_number): Remove function.
(newunit_alloc): New function.
(newunit_free): New function.
* io/transfer.c (data_transfer_init): Check for invalid unit
number.
2016-10-09 Janne Blomqvist <jb@gcc.gnu.org>
PR libfortran/67585

5
libgfortran/io/io.h
View File

@ -715,8 +715,9 @@ internal_proto (finish_last_advance_record);
extern int unit_truncate (gfc_unit *, gfc_offset, st_parameter_common *);
internal_proto (unit_truncate);
extern GFC_INTEGER_4 get_unique_unit_number (st_parameter_common *);
internal_proto(get_unique_unit_number);
extern int newunit_alloc (void);
internal_proto(newunit_alloc);
/* open.c */

2
libgfortran/io/open.c
View File

@ -812,7 +812,7 @@ st_open (st_parameter_open *opp)
if ((opp->common.flags & IOPARM_LIBRETURN_MASK) == IOPARM_LIBRETURN_OK)
{
if ((opp->common.flags & IOPARM_OPEN_HAS_NEWUNIT))
opp->common.unit = get_unique_unit_number(&opp->common);
opp->common.unit = newunit_alloc ();
else if (opp->common.unit < 0)
{
u = find_unit (opp->common.unit);

10
libgfortran/io/transfer.c
View File

@ -2601,7 +2601,15 @@ data_transfer_init (st_parameter_dt *dtp, int read_flag)
dtp->u.p.current_unit = get_unit (dtp, 1);
if (dtp->u.p.current_unit->s == NULL)
if (dtp->u.p.current_unit == NULL)
{
/* This means we tried to access an external unit < 0 without
having opened it first with NEWUNIT=. */
generate_error (&dtp->common, LIBERROR_BAD_OPTION,
"Invalid unit number in statement");
return;
}
else if (dtp->u.p.current_unit->s == NULL)
{ /* Open the unit with some default flags. */
st_parameter_open opp;
unit_convert conv;

108
libgfortran/io/unit.c
View File

@ -29,6 +29,7 @@ see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
#include "unix.h"
#include <stdlib.h>
#include <string.h>
#include <assert.h>
/* IO locking rules:
@ -68,12 +69,34 @@ see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
on it. unlock_unit or close_unit must be always called only with the
private lock held. */
/* Subroutines related to units */
/* Unit number to be assigned when NEWUNIT is used in an OPEN statement. */
#define GFC_FIRST_NEWUNIT -10
/* Table of allocated newunit values. A simple solution would be to
map OS file descriptors (fd's) to unit numbers, e.g. with newunit =
-fd - 2, however that doesn't work since Fortran allows an existing
unit number to be reassociated with a new file. Thus the simple
approach may lead to a situation where we'd try to assign a
(negative) unit number which already exists. Hence we must keep
track of allocated newunit values ourselves. This is the purpose of
the newunits array. The indices map to newunit values as newunit =
-index + NEWUNIT_FIRST. E.g. newunits[0] having the value true
means that a unit with number NEWUNIT_FIRST exists. Similar to
POSIX file descriptors, we always allocate the lowest (in absolute
value) available unit number.
*/
static bool *newunits;
static int newunit_size; /* Total number of elements in the newunits array. */
/* Low water indicator for the newunits array. Below the LWI all the
units are allocated, above and equal to the LWI there may be both
allocated and free units. */
static int newunit_lwi;
static void newunit_free (int);
/* Unit numbers assigned with NEWUNIT start from here. */
#define NEWUNIT_START -10
#define NEWUNIT_STACK_SIZE 16
static GFC_INTEGER_4 next_available_newunit = GFC_FIRST_NEWUNIT;
/* A stack to save previously used newunit-assigned unit numbers to
allow them to be reused without reallocating the gfc_unit structure
@ -81,6 +104,7 @@ static GFC_INTEGER_4 next_available_newunit = GFC_FIRST_NEWUNIT;
static gfc_saved_unit newunit_stack[NEWUNIT_STACK_SIZE];
static int newunit_tos = 0; /* Index to Top of Stack. */
#define CACHE_SIZE 3
static gfc_unit *unit_cache[CACHE_SIZE];
gfc_offset max_offset;
@ -551,7 +575,7 @@ get_unit (st_parameter_dt *dtp, int do_create)
if ((dtp->common.flags & IOPARM_DT_HAS_UDTIO) != 0)
{
dtp->u.p.unit_is_internal = 1;
dtp->common.unit = get_unique_unit_number (&dtp->common);
dtp->common.unit = newunit_alloc ();
unit = get_gfc_unit (dtp->common.unit, do_create);
set_internal_unit (dtp, unit, kind);
fbuf_init (unit, 128);
@ -567,7 +591,7 @@ get_unit (st_parameter_dt *dtp, int do_create)
}
else
{
dtp->common.unit = get_unique_unit_number (&dtp->common);
dtp->common.unit = newunit_alloc ();
unit = xcalloc (1, sizeof (gfc_unit));
fbuf_init (unit, 128);
}
@ -579,8 +603,12 @@ get_unit (st_parameter_dt *dtp, int do_create)
dtp->u.p.unit_is_internal = 0;
dtp->internal_unit = NULL;
dtp->internal_unit_desc = NULL;
unit = get_gfc_unit (dtp->common.unit, do_create);
return unit;
/* For an external unit with unit number < 0 creating it on the fly
is not allowed, such units must be created with
OPEN(NEWUNIT=...). */
if (dtp->common.unit < 0)
return get_gfc_unit (dtp->common.unit, 0);
return get_gfc_unit (dtp->common.unit, do_create);
}
@ -734,6 +762,9 @@ close_unit_1 (gfc_unit *u, int locked)
free_format_hash_table (u);
fbuf_destroy (u);
if (u->unit_number <= NEWUNIT_START)
newunit_free (u->unit_number);
if (!locked)
__gthread_mutex_unlock (&u->lock);
@ -788,6 +819,9 @@ close_units (void)
free (newunit_stack[newunit_tos].unit->s);
free (newunit_stack[newunit_tos--].unit);
}
free (newunits);
#ifdef HAVE_FREELOCALE
freelocale (c_locale);
#endif
@ -885,25 +919,53 @@ finish_last_advance_record (gfc_unit *u)
fbuf_flush (u, u->mode);
}
/* Assign a negative number for NEWUNIT in OPEN statements or for
internal units. */
GFC_INTEGER_4
get_unique_unit_number (st_parameter_common *common)
int
newunit_alloc (void)
{
GFC_INTEGER_4 num;
#ifdef HAVE_SYNC_FETCH_AND_ADD
num = __sync_fetch_and_add (&next_available_newunit, -1);
#else
__gthread_mutex_lock (&unit_lock);
num = next_available_newunit--;
__gthread_mutex_unlock (&unit_lock);
#endif
/* Do not allow NEWUNIT numbers to wrap. */
if (num > GFC_FIRST_NEWUNIT)
if (!newunits)
{
generate_error (common, LIBERROR_INTERNAL, "NEWUNIT exhausted");
return 0;
newunits = xcalloc (16, 1);
newunit_size = 16;
}
return num;
/* Search for the next available newunit. */
for (int ii = newunit_lwi; ii < newunit_size; ii++)
{
if (!newunits[ii])
{
newunits[ii] = true;
newunit_lwi = ii + 1;
__gthread_mutex_unlock (&unit_lock);
return -ii + NEWUNIT_START;
}
}
/* Search failed, bump size of array and allocate the first
available unit. */
int old_size = newunit_size;
newunit_size *= 2;
newunits = xrealloc (newunits, newunit_size);
memset (newunits + old_size, 0, old_size);
newunits[old_size] = true;
newunit_lwi = old_size + 1;
__gthread_mutex_unlock (&unit_lock);
return -old_size + NEWUNIT_START;
}
/* Free a previously allocated newunit= unit number. unit_lock must
be held when calling. */
static void
newunit_free (int unit)
{
int ind = -unit + NEWUNIT_START;
assert(ind >= 0 && ind < newunit_size);
newunits[ind] = false;
if (ind < newunit_lwi)
newunit_lwi = ind;
}