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Make dotlock.c thread-safe on pthread systems.

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This is achieved by passing the define DOTLOCK_USE_PTHREAD.
This commit is contained in:
Werner Koch 2011-09-29 15:27:01 +02:00
parent ed8e267859
commit bf3d5beb71
2 changed files with 81 additions and 25 deletions
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7
common/ChangeLog
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@ -1,3 +1,10 @@
2011-09-29 Werner Koch <wk@g10code.com>
* dotlock.c (DOTLOCK_USE_PTHREAD): New macro.
[DOTLOCK_USE_PTHREAD] (all_lockfiles_mutex): New.
(LOCK_all_lockfiles, UNLOCK_all_lockfiles): New. Use them to
protect access to all_lockfiles.
2011-09-28 Werner Koch <wk@g10code.com>
* dotlock.c (dotlock_take, dotlock_take_unix, dotlock_take_w32):

99
common/dotlock.c
View File

@ -57,7 +57,8 @@
This installs an atexit handler and may also initialize mutex etc.
It is optional for non-threaded applications. Only the first call
has an effect.
has an effect. This needs to be done before any extra threads are
started.
To create a lock file (which prepares it but does not take the
lock) you do:
@ -71,12 +72,14 @@
It is important to handle the error. For example on a read-only
file system a lock can't be created (but is usually not needed).
FNAME is the file you want to lock; the actual lockfile is that
name with the suffix ".lock" appended. This call creates a unique
file temporary file (".#lk*") in the same directory as FNAME and
returns a handle for further operations. The module keeps track of
theses unique files so that they will be unlinked using the atexit
handler. If you don't need the lock file anymore, you may also
explicitly remove it with a call to:
name with the suffix ".lock" appended. On success a handle to be
used with the other functions is returned or NULL on error. Note
that the handle shall only be used by one thread at a time. This
function creates a unique file temporary file (".#lk*") in the same
directory as FNAME and returns a handle for further operations.
The module keeps track of theses unique files so that they will be
unlinked using the atexit handler. If you don't need the lock file
anymore, you may also explicitly remove it with a call to:
dotlock_destroy (h);
@ -124,6 +127,8 @@
to pass -DHAVE_CONFIG_H to the compiler. Macros used by this
module are:
DOTLOCK_USE_PTHREAD - Define if POSIX threads are in use.
DOTLOCK_GLIB_LOGGING - Define this to use Glib logging functions.
GNUPG_MAJOR_VERSION - Defined when used by GnuPG.
@ -150,6 +155,12 @@
it on the command line, remember to pass -D_FILE_OFFSET_BITS=64
Bugs:
=====
On Windows this module is not yet thread-safe.
Miscellaneous notes:
====================
@ -227,6 +238,9 @@
#ifdef HAVE_SIGNAL_H
# include <signal.h>
#endif
#ifdef DOTLOCK_USE_PTHREAD
# include <pthread.h>
#endif
#ifdef DOTLOCK_GLIB_LOGGING
# include <glib.h>
@ -285,6 +299,7 @@
# define my_error_1(a,b) log_error ((a), (b))
# define my_error_2(a,b,c) log_error ((a), (b), (c))
# define my_debug_1(a,b) log_debug ((a), (b))
# define my_fatal_0(a) log_fatal ((a))
#elif defined (DOTLOCK_GLIB_LOGGING)
# define my_info_0(a) g_message ((a))
# define my_info_1(a,b) g_message ((a), (b))
@ -294,6 +309,7 @@
# define my_error_1(a,b) g_warning ((a), (b))
# define my_error_2(a,b,c g_warning ((a), (b), (c))
# define my_debug_1(a,b) g_debug ((a), (b))
# define my_fatal_0(a) g_error ((a))
#else
# define my_info_0(a) fprintf (stderr, (a))
# define my_info_1(a,b) fprintf (stderr, (a), (b))
@ -303,6 +319,8 @@
# define my_error_1(a,b) fprintf (stderr, (a), (b))
# define my_error_2(a,b,c) fprintf (stderr, (a), (b), (c))
# define my_debug_1(a,b) fprintf (stderr, (a), (b))
# define my_fatal_0(a) do { fprintf (stderr,(a)); fflush (stderr); \
abort (); } while (0)
#endif
@ -331,11 +349,27 @@ struct dotlock_handle
/* A list of of all lock handles. The volatile attribute might help
if used in an atexit handler. */
static volatile dotlock_t all_lockfiles;
#ifdef DOTLOCK_USE_PTHREAD
static pthread_mutex_t all_lockfiles_mutex = PTHREAD_MUTEX_INITIALIZER;
# define LOCK_all_lockfiles() do { \
if (pthread_mutex_lock (&all_lockfiles_mutex)) \
my_fatal_0 ("locking all_lockfiles_mutex failed\n"); \
} while (0)
# define UNLOCK_all_lockfiles() do { \
if (pthread_mutex_unlock (&all_lockfiles_mutex)) \
my_fatal_0 ("unlocking all_lockfiles_mutex failed\n"); \
} while (0)
#else /*!DOTLOCK_USE_PTHREAD*/
# define LOCK_all_lockfiles() do { } while (0)
# define UNLOCK_all_lockfiles() do { } while (0)
#endif /*!DOTLOCK_USE_PTHREAD*/
/* If this has the value true all locking is disabled. */
static int never_lock;
/* Entirely disable all locking. This function should be called
before any locking is done. It may be called right at startup of
@ -352,13 +386,19 @@ static int
maybe_deadlock (dotlock_t h)
{
dotlock_t r;
int res = 0;
for ( r=all_lockfiles; r; r = r->next )
LOCK_all_lockfiles ();
for (r=all_lockfiles; r; r = r->next)
{
if ( r != h && r->locked )
return 1;
{
res = 1;
break;
}
}
return 0;
UNLOCK_all_lockfiles ();
return res;
}
#endif /*HAVE_POSIX_SYSTEM*/
@ -528,9 +568,7 @@ dotlock_create_unix (dotlock_t h, const char *file_to_lock)
dirpart = file_to_lock;
}
#ifdef _REENTRANT
/* fixme: aquire mutex on all_lockfiles */
#endif
LOCK_all_lockfiles ();
h->next = all_lockfiles;
all_lockfiles = h;
@ -539,6 +577,7 @@ dotlock_create_unix (dotlock_t h, const char *file_to_lock)
if (!h->tname)
{
all_lockfiles = h->next;
UNLOCK_all_lockfiles ();
jnlib_free (h);
return NULL;
}
@ -560,6 +599,7 @@ dotlock_create_unix (dotlock_t h, const char *file_to_lock)
if ( fd == -1 )
{
all_lockfiles = h->next;
UNLOCK_all_lockfiles ();
my_error_2 (_("failed to create temporary file `%s': %s\n"),
h->tname, strerror(errno));
jnlib_free (h->tname);
@ -590,19 +630,18 @@ dotlock_create_unix (dotlock_t h, const char *file_to_lock)
goto write_failed;
}
# ifdef _REENTRANT
/* release mutex */
# endif
h->lockname = jnlib_malloc (strlen (file_to_lock) + 6 );
if (!h->lockname)
{
all_lockfiles = h->next;
UNLOCK_all_lockfiles ();
unlink (h->tname);
jnlib_free (h->tname);
jnlib_free (h);
return NULL;
}
strcpy (stpcpy (h->lockname, file_to_lock), EXTSEP_S "lock");
UNLOCK_all_lockfiles ();
if (h->use_o_excl)
my_debug_1 ("locking for `%s' done via O_EXCL\n", h->lockname);
@ -610,9 +649,7 @@ dotlock_create_unix (dotlock_t h, const char *file_to_lock)
write_failed:
all_lockfiles = h->next;
# ifdef _REENTRANT
/* fixme: release mutex */
# endif
UNLOCK_all_lockfiles ();
my_error_2 (_("error writing to `%s': %s\n"), h->tname, strerror (errno));
close (fd);
unlink (h->tname);
@ -632,6 +669,7 @@ dotlock_create_unix (dotlock_t h, const char *file_to_lock)
static dotlock_t
dotlock_create_w32 (dotlock_t h, const char *file_to_lock)
{
LOCK_all_lockfiles ();
h->next = all_lockfiles;
all_lockfiles = h;
@ -639,6 +677,7 @@ dotlock_create_w32 (dotlock_t h, const char *file_to_lock)
if (!h->lockname)
{
all_lockfiles = h->next;
UNLOCK_all_lockfiles ();
jnlib_free (h);
return NULL;
}
@ -673,8 +712,9 @@ dotlock_create_w32 (dotlock_t h, const char *file_to_lock)
}
if (h->lockhd == INVALID_HANDLE_VALUE)
{
my_error_2 (_("can't create `%s': %s\n"), h->lockname, w32_strerror (-1));
all_lockfiles = h->next;
UNLOCK_all_lockfiles ();
my_error_2 (_("can't create `%s': %s\n"), h->lockname, w32_strerror (-1));
jnlib_free (h->lockname);
jnlib_free (h);
return NULL;
@ -733,11 +773,10 @@ dotlock_create (const char *file_to_lock, unsigned int flags)
if (never_lock)
{
h->disable = 1;
#ifdef _REENTRANT
/* fixme: aquire mutex on all_lockfiles */
#endif
LOCK_all_lockfiles ();
h->next = all_lockfiles;
all_lockfiles = h;
UNLOCK_all_lockfiles ();
return h;
}
@ -791,6 +830,7 @@ dotlock_destroy (dotlock_t h)
return;
/* First remove the handle from our global list of all locks. */
LOCK_all_lockfiles ();
for (hprev=NULL, htmp=all_lockfiles; htmp; hprev=htmp, htmp=htmp->next)
if (htmp == h)
{
@ -801,6 +841,7 @@ dotlock_destroy (dotlock_t h)
h->next = NULL;
break;
}
UNLOCK_all_lockfiles ();
/* Then destroy the lock. */
if (!h->disable)
@ -1123,7 +1164,10 @@ dotlock_release (dotlock_t h)
any locks left. It might happen that another atexit handler
tries to release the lock while the atexit handler of this module
already ran and thus H is undefined. */
if (!all_lockfiles)
LOCK_all_lockfiles ();
ret = !all_lockfiles;
UNLOCK_all_lockfiles ();
if (ret)
return 0;
if ( h->disable )
@ -1148,7 +1192,7 @@ dotlock_release (dotlock_t h)
/* Remove all lockfiles. This is usually called by the atexit handler
/* Remove all lockfiles. This is called by the atexit handler
installed by this module but may also be called by other
termination handlers. */
void
@ -1156,8 +1200,13 @@ dotlock_remove_lockfiles (void)
{
dotlock_t h, h2;
/* First set the lockfiles list to NULL so that for example
dotlock_release is ware that this fucntion is currently
running. */
LOCK_all_lockfiles ();
h = all_lockfiles;
all_lockfiles = NULL;
UNLOCK_all_lockfiles ();
while ( h )
{