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repo: Require lock type in ostree_repo_lock_pop 

This simplifies the lock state management considerably since the
previously pushed type doesn't need to be tracked. Instead, 2 counters
are kept to track how many times each lock type has been pushed. When
the number of exclusive locks drops to 0, the lock transitions back to
shared.
This commit is contained in:
Dan Nicholson 2021-04-28 21:13:15 -06:00
parent 0f36d8c221
commit c3ada6fa7a
4 changed files with 132 additions and 71 deletions
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4
src/libostree/ostree-repo-commit.c
View File

@ -2341,7 +2341,7 @@ ostree_repo_commit_transaction (OstreeRepo *self,
if (self->txn_locked)
{
if (!ostree_repo_lock_pop (self, cancellable, error))
if (!ostree_repo_lock_pop (self, OSTREE_REPO_LOCK_SHARED, cancellable, error))
return FALSE;
self->txn_locked = FALSE;
}
@ -2399,7 +2399,7 @@ ostree_repo_abort_transaction (OstreeRepo *self,
if (self->txn_locked)
{
if (!ostree_repo_lock_pop (self, cancellable, error))
if (!ostree_repo_lock_pop (self, OSTREE_REPO_LOCK_SHARED, cancellable, error))
return FALSE;
self->txn_locked = FALSE;
}

170
src/libostree/ostree-repo.c
View File

@ -214,7 +214,8 @@ static GPrivate repo_lock_table = G_PRIVATE_INIT (free_repo_lock_table);
typedef struct {
int fd;
GQueue stack;
guint shared; /* Number of shared locks */
guint exclusive; /* Number of exclusive locks */
} OstreeRepoLock;
typedef struct {
@ -223,6 +224,22 @@ typedef struct {
const char *name;
} OstreeRepoLockInfo;
static const char *
lock_state_name (int state)
{
switch (state)
{
case LOCK_EX:
return "exclusive";
case LOCK_SH:
return "shared";
case LOCK_UN:
return "unlocked";
default:
g_assert_not_reached ();
}
}
static void
repo_lock_info (OstreeRepoLock *lock, OstreeRepoLockInfo *out_info)
{
@ -230,17 +247,14 @@ repo_lock_info (OstreeRepoLock *lock, OstreeRepoLockInfo *out_info)
g_assert (out_info != NULL);
OstreeRepoLockInfo info;
info.len = g_queue_get_length (&lock->stack);
info.len = lock->shared + lock->exclusive;
if (info.len == 0)
{
info.state = LOCK_UN;
info.name = "unlocked";
}
else if (lock->exclusive > 0)
info.state = LOCK_EX;
else
{
info.state = GPOINTER_TO_INT (g_queue_peek_head (&lock->stack));
info.name = (info.state == LOCK_EX) ? "exclusive" : "shared";
}
info.state = LOCK_SH;
info.name = lock_state_name (info.state);
*out_info = info;
}
@ -256,7 +270,6 @@ free_repo_lock (gpointer data)
repo_lock_info (lock, &info);
g_debug ("Free lock: state=%s, depth=%u", info.name, info.len);
g_queue_clear (&lock->stack);
if (lock->fd >= 0)
{
g_debug ("Closing repo lock file");
@ -339,6 +352,7 @@ push_repo_lock (OstreeRepo *self,
GError **error)
{
int flags = (lock_type == OSTREE_REPO_LOCK_EXCLUSIVE) ? LOCK_EX : LOCK_SH;
int next_state = flags;
if (!blocking)
flags |= LOCK_NB;
@ -355,7 +369,6 @@ push_repo_lock (OstreeRepo *self,
if (lock == NULL)
{
lock = g_new0 (OstreeRepoLock, 1);
g_queue_init (&lock->stack);
g_debug ("Opening repo lock file");
lock->fd = TEMP_FAILURE_RETRY (openat (self->repo_dir_fd, ".lock",
O_CREAT | O_RDWR | O_CLOEXEC,
@ -374,29 +387,40 @@ push_repo_lock (OstreeRepo *self,
repo_lock_info (lock, &info);
g_debug ("Push lock: state=%s, depth=%u", info.name, info.len);
if (info.state == LOCK_EX)
guint *counter;
if (next_state == LOCK_EX)
counter = &(lock->exclusive);
else
counter = &(lock->shared);
/* Check for overflow */
g_assert_cmpuint (*counter, <, G_MAXUINT);
if (info.state == LOCK_EX || info.state == next_state)
{
g_debug ("Repo already locked exclusively, extending stack");
g_queue_push_head (&lock->stack, GINT_TO_POINTER (LOCK_EX));
g_debug ("Repo already locked %s, maintaining state", info.name);
}
else
{
int next_state = (flags & LOCK_EX) ? LOCK_EX : LOCK_SH;
const char *next_state_name = (flags & LOCK_EX) ? "exclusive" : "shared";
/* We should never upgrade from exclusive to shared */
g_assert (!(info.state == LOCK_EX && next_state == LOCK_SH));
const char *next_state_name = lock_state_name (next_state);
g_debug ("Locking repo %s", next_state_name);
if (!do_repo_lock (lock->fd, flags))
return glnx_throw_errno_prefix (error, "Locking repo %s failed",
next_state_name);
g_queue_push_head (&lock->stack, GINT_TO_POINTER (next_state));
}
/* Update state */
(*counter)++;
return TRUE;
}
static gboolean
pop_repo_lock (OstreeRepo *self,
OstreeRepoLockType lock_type,
gboolean blocking,
GError **error)
{
@ -412,14 +436,46 @@ pop_repo_lock (OstreeRepo *self,
OstreeRepoLockInfo info;
repo_lock_info (lock, &info);
g_return_val_if_fail (info.len > 0, FALSE);
g_debug ("Pop lock: state=%s, depth=%u", info.name, info.len);
if (info.len > 1)
{
int next_state = GPOINTER_TO_INT (g_queue_peek_nth (&lock->stack, 1));
/* Drop back to the previous lock state if it differs */
if (next_state != info.state)
int state_to_drop;
guint *counter;
if (lock_type == OSTREE_REPO_LOCK_EXCLUSIVE)
{
state_to_drop = LOCK_EX;
counter = &(lock->exclusive);
}
else
{
state_to_drop = LOCK_SH;
counter = &(lock->shared);
}
/* Make sure caller specified a valid type to release */
g_assert_cmpuint (*counter, >, 0);
int next_state;
if (info.len == 1)
{
/* Lock counters will be empty, unlock */
next_state = LOCK_UN;
}
else if (state_to_drop == LOCK_EX)
next_state = (lock->exclusive > 1) ? LOCK_EX : LOCK_SH;
else
next_state = (lock->exclusive > 0) ? LOCK_EX : LOCK_SH;
if (next_state == LOCK_UN)
{
g_debug ("Unlocking repo");
if (!do_repo_unlock (lock->fd, flags))
return glnx_throw_errno_prefix (error, "Unlocking repo failed");
}
else if (info.state == next_state)
{
g_debug ("Maintaining lock state as %s", info.name);
}
else
{
/* We should never drop from shared to exclusive */
g_return_val_if_fail (next_state == LOCK_SH, FALSE);
@ -428,18 +484,9 @@ pop_repo_lock (OstreeRepo *self,
return glnx_throw_errno_prefix (error,
"Setting repo lock to shared failed");
}
else
g_debug ("Maintaining lock state as %s", info.name);
}
else
{
/* Lock stack will be empty, unlock */
g_debug ("Unlocking repo");
if (!do_repo_unlock (lock->fd, flags))
return glnx_throw_errno_prefix (error, "Unlocking repo failed");
}
g_queue_pop_head (&lock->stack);
/* Update state */
(*counter)--;
return TRUE;
}
@ -451,13 +498,13 @@ pop_repo_lock (OstreeRepo *self,
* @cancellable: a #GCancellable
* @error: a #GError
*
* Takes a lock on the repository and adds it to the lock stack. If @lock_type
* Takes a lock on the repository and adds it to the lock state. If @lock_type
* is %OSTREE_REPO_LOCK_SHARED, a shared lock is taken. If @lock_type is
* %OSTREE_REPO_LOCK_EXCLUSIVE, an exclusive lock is taken. The actual lock
* state is only changed when locking a previously unlocked repository or
* upgrading the lock from shared to exclusive. If the requested lock state is
* upgrading the lock from shared to exclusive. If the requested lock type is
* unchanged or would represent a downgrade (exclusive to shared), the lock
* state is not changed and the stack is simply updated.
* state is not changed.
*
* ostree_repo_lock_push() waits for the lock depending on the repository's
* lock-timeout-secs configuration. When lock-timeout-secs is -1, a blocking lock is
@ -542,13 +589,16 @@ ostree_repo_lock_push (OstreeRepo *self,
/**
* ostree_repo_lock_pop:
* @self: a #OstreeRepo
* @lock_type: the type of lock to release
* @cancellable: a #GCancellable
* @error: a #GError
*
* Remove the current repository lock state from the lock stack. If the lock
* stack becomes empty, the repository is unlocked. Otherwise, the lock state
* only changes when transitioning from an exclusive lock back to a shared
* lock.
* Release a lock of type @lock_type from the lock state. If the lock state
* becomes empty, the repository is unlocked. Otherwise, the lock state only
* changes when transitioning from an exclusive lock back to a shared lock. The
* requested @lock_type must be the same type that was requested in the call to
* ostree_repo_lock_push(). It is a programmer error if these do not match and
* the program may abort if the lock would reach an invalid state.
*
* ostree_repo_lock_pop() waits for the lock depending on the repository's
* lock-timeout-secs configuration. When lock-timeout-secs is -1, a blocking lock is
@ -565,6 +615,7 @@ ostree_repo_lock_push (OstreeRepo *self,
*/
gboolean
ostree_repo_lock_pop (OstreeRepo *self,
OstreeRepoLockType lock_type,
GCancellable *cancellable,
GError **error)
{
@ -583,7 +634,7 @@ ostree_repo_lock_pop (OstreeRepo *self,
else if (self->lock_timeout_seconds == REPO_LOCK_BLOCKING)
{
g_debug ("Popping lock blocking");
return pop_repo_lock (self, TRUE, error);
return pop_repo_lock (self, lock_type, TRUE, error);
}
else
{
@ -598,7 +649,7 @@ ostree_repo_lock_pop (OstreeRepo *self,
return FALSE;
g_autoptr(GError) local_error = NULL;
if (pop_repo_lock (self, FALSE, &local_error))
if (pop_repo_lock (self, lock_type, FALSE, &local_error))
return TRUE;
if (!g_error_matches (local_error, G_IO_ERROR,
@ -629,18 +680,22 @@ ostree_repo_lock_pop (OstreeRepo *self,
}
}
/*
struct OstreeRepoAutoLock {
OstreeRepo *repo;
OstreeRepoLockType lock_type;
};
/**
* ostree_repo_auto_lock_push: (skip)
* @self: a #OstreeRepo
* @lock_type: the type of lock to acquire
* @cancellable: a #GCancellable
* @error: a #GError
*
* Like ostree_repo_lock_push(), but for usage with #OstreeRepoAutoLock.
* The intended usage is to declare the #OstreeRepoAutoLock with
* g_autoptr() so that ostree_repo_auto_lock_cleanup() is called when it
* goes out of scope. This will automatically pop the lock status off
* the stack if it was acquired successfully.
* Like ostree_repo_lock_push(), but for usage with #OstreeRepoAutoLock. The
* intended usage is to declare the #OstreeRepoAutoLock with g_autoptr() so
* that ostree_repo_auto_lock_cleanup() is called when it goes out of scope.
* This will automatically release the lock if it was acquired successfully.
*
* |[<!-- language="C" -->
* g_autoptr(OstreeRepoAutoLock) lock = NULL;
@ -660,7 +715,11 @@ ostree_repo_auto_lock_push (OstreeRepo *self,
{
if (!ostree_repo_lock_push (self, lock_type, cancellable, error))
return NULL;
return (OstreeRepoAutoLock *)self;
OstreeRepoAutoLock *auto_lock = g_slice_new (OstreeRepoAutoLock);
auto_lock->repo = self;
auto_lock->lock_type = lock_type;
return auto_lock;
}
/**
@ -674,18 +733,19 @@ ostree_repo_auto_lock_push (OstreeRepo *self,
* Since: 2021.3
*/
void
ostree_repo_auto_lock_cleanup (OstreeRepoAutoLock *lock)
ostree_repo_auto_lock_cleanup (OstreeRepoAutoLock *auto_lock)
{
OstreeRepo *repo = lock;
if (repo)
if (auto_lock != NULL)
{
g_autoptr(GError) error = NULL;
int errsv = errno;
if (!ostree_repo_lock_pop (repo, NULL, &error))
if (!ostree_repo_lock_pop (auto_lock->repo, auto_lock->lock_type, NULL, &error))
g_critical ("Cleanup repo lock failed: %s", error->message);
errno = errsv;
g_slice_free (OstreeRepoAutoLock, auto_lock);
}
}

3
src/libostree/ostree-repo.h
View File

@ -1520,6 +1520,7 @@ gboolean ostree_repo_lock_push (OstreeRepo *self,
GError **error);
_OSTREE_PUBLIC
gboolean ostree_repo_lock_pop (OstreeRepo *self,
OstreeRepoLockType lock_type,
GCancellable *cancellable,
GError **error);
@ -1533,7 +1534,7 @@ gboolean ostree_repo_lock_pop (OstreeRepo *self,
*
* Since: 2021.3
*/
typedef OstreeRepo OstreeRepoAutoLock;
typedef struct OstreeRepoAutoLock OstreeRepoAutoLock;
_OSTREE_PUBLIC
OstreeRepoAutoLock * ostree_repo_auto_lock_push (OstreeRepo *self,

6
tests/test-core.js
View File

@ -137,9 +137,9 @@ assertEquals(actual_checksum, networks_checksum)
// Basic locking API sanity test
repo.lock_push(OSTree.RepoLockType.SHARED, null);
repo.lock_push(OSTree.RepoLockType.SHARED, null);
repo.lock_pop(null);
repo.lock_pop(null);
repo.lock_pop(OSTree.RepoLockType.SHARED, null);
repo.lock_pop(OSTree.RepoLockType.SHARED, null);
repo.lock_push(OSTree.RepoLockType.EXCLUSIVE, null);
repo.lock_pop(null);
repo.lock_pop(OSTree.RepoLockType.EXCLUSIVE, null);
print("ok test-core");