diff options
Diffstat (limited to 'libpod/lock/shm')
-rw-r--r-- | libpod/lock/shm/shm_lock.c | 452 | ||||
-rw-r--r-- | libpod/lock/shm/shm_lock.go | 216 | ||||
-rw-r--r-- | libpod/lock/shm/shm_lock.h | 46 | ||||
-rw-r--r-- | libpod/lock/shm/shm_lock_test.go | 278 |
4 files changed, 992 insertions, 0 deletions
diff --git a/libpod/lock/shm/shm_lock.c b/libpod/lock/shm/shm_lock.c new file mode 100644 index 000000000..4af58d857 --- /dev/null +++ b/libpod/lock/shm/shm_lock.c @@ -0,0 +1,452 @@ +#include <errno.h> +#include <fcntl.h> +#include <pthread.h> +#include <stdbool.h> +#include <stdint.h> +#include <stdlib.h> +#include <sys/mman.h> +#include <sys/stat.h> +#include <sys/types.h> +#include <unistd.h> + +#include "shm_lock.h" + +// Compute the size of the SHM struct +static size_t compute_shm_size(uint32_t num_bitmaps) { + return sizeof(shm_struct_t) + (num_bitmaps * sizeof(lock_group_t)); +} + +// Take the given mutex. +// Handles exceptional conditions, including a mutex locked by a process that +// died holding it. +// Returns 0 on success, or positive errno on failure. +static int take_mutex(pthread_mutex_t *mutex) { + int ret_code; + + do { + ret_code = pthread_mutex_lock(mutex); + } while(ret_code == EAGAIN); + + if (ret_code == EOWNERDEAD) { + // The previous owner of the mutex died while holding it + // Take it for ourselves + ret_code = pthread_mutex_consistent(mutex); + if (ret_code != 0) { + // Someone else may have gotten here first and marked the state consistent + // However, the mutex could also be invalid. + // Fail here instead of looping back to trying to lock the mutex. + return ret_code; + } + } else if (ret_code != 0) { + return ret_code; + } + + return 0; +} + +// Release the given mutex. +// Returns 0 on success, or positive errno on failure. +static int release_mutex(pthread_mutex_t *mutex) { + int ret_code; + + do { + ret_code = pthread_mutex_unlock(mutex); + } while(ret_code == EAGAIN); + + if (ret_code != 0) { + return ret_code; + } + + return 0; +} + +// Set up an SHM segment holding locks for libpod. +// num_locks must not be 0. +// Path is the path to the SHM segment. It must begin with a single / and +// container no other / characters, and be at most 255 characters including +// terminating NULL byte. +// Returns a valid pointer on success or NULL on error. +// If an error occurs, negative ERRNO values will be written to error_code. +shm_struct_t *setup_lock_shm(char *path, uint32_t num_locks, int *error_code) { + int shm_fd, i, j, ret_code; + uint32_t num_bitmaps; + size_t shm_size; + shm_struct_t *shm; + pthread_mutexattr_t attr; + + // If error_code doesn't point to anything, we can't reasonably return errors + // So fail immediately + if (error_code == NULL) { + return NULL; + } + + // We need a nonzero number of locks + if (num_locks == 0) { + *error_code = -1 * EINVAL; + return NULL; + } + + if (path == NULL) { + *error_code = -1 * EINVAL; + return NULL; + } + + // Calculate the number of bitmaps required + num_bitmaps = num_locks / BITMAP_SIZE; + if (num_locks % BITMAP_SIZE != 0) { + // The actual number given is not an even multiple of our bitmap size + // So round up + num_bitmaps += 1; + } + + // Calculate size of the shm segment + shm_size = compute_shm_size(num_bitmaps); + + // Create a new SHM segment for us + shm_fd = shm_open(path, O_RDWR | O_CREAT | O_EXCL, 0600); + if (shm_fd < 0) { + *error_code = -1 * errno; + return NULL; + } + + // Increase its size to what we need + ret_code = ftruncate(shm_fd, shm_size); + if (ret_code < 0) { + *error_code = -1 * errno; + goto CLEANUP_UNLINK; + } + + // Map the shared memory in + shm = mmap(NULL, shm_size, PROT_READ | PROT_WRITE, MAP_SHARED, shm_fd, 0); + if (shm == MAP_FAILED) { + *error_code = -1 * errno; + goto CLEANUP_UNLINK; + } + + // We have successfully mapped the memory, now initialize the region + shm->magic = MAGIC; + shm->unused = 0; + shm->num_locks = num_bitmaps * BITMAP_SIZE; + shm->num_bitmaps = num_bitmaps; + + // Create an initializer for our pthread mutexes + ret_code = pthread_mutexattr_init(&attr); + if (ret_code != 0) { + *error_code = -1 * ret_code; + goto CLEANUP_UNMAP; + } + + // Set mutexes to pshared - multiprocess-safe + ret_code = pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_SHARED); + if (ret_code != 0) { + *error_code = -1 * ret_code; + goto CLEANUP_FREEATTR; + } + + // Set mutexes to robust - if a process dies while holding a mutex, we'll get + // a special error code on the next attempt to lock it. + // This should prevent panicing processes from leaving the state unusable. + ret_code = pthread_mutexattr_setrobust(&attr, PTHREAD_MUTEX_ROBUST); + if (ret_code != 0) { + *error_code = -1 * ret_code; + goto CLEANUP_FREEATTR; + } + + // Initialize the mutex that protects the bitmaps using the mutex attributes + ret_code = pthread_mutex_init(&(shm->segment_lock), &attr); + if (ret_code != 0) { + *error_code = -1 * ret_code; + goto CLEANUP_FREEATTR; + } + + // Initialize all bitmaps to 0 initially + // And initialize all semaphores they use + for (i = 0; i < num_bitmaps; i++) { + shm->locks[i].bitmap = 0; + for (j = 0; j < BITMAP_SIZE; j++) { + // Initialize each mutex + ret_code = pthread_mutex_init(&(shm->locks[i].locks[j]), &attr); + if (ret_code != 0) { + *error_code = -1 * ret_code; + goto CLEANUP_FREEATTR; + } + } + } + + // Close the file descriptor, we're done with it + // Ignore errors, it's ok if we leak a single FD and this should only run once + close(shm_fd); + + // Destroy the pthread initializer attribute. + // Again, ignore errors, this will only run once and we might leak a tiny bit + // of memory at worst. + pthread_mutexattr_destroy(&attr); + + return shm; + + // Cleanup after an error + CLEANUP_FREEATTR: + pthread_mutexattr_destroy(&attr); + CLEANUP_UNMAP: + munmap(shm, shm_size); + CLEANUP_UNLINK: + close(shm_fd); + shm_unlink(path); + return NULL; +} + +// Open an existing SHM segment holding libpod locks. +// num_locks is the number of locks that will be configured in the SHM segment. +// num_locks cannot be 0. +// Path is the path to the SHM segment. It must begin with a single / and +// container no other / characters, and be at most 255 characters including +// terminating NULL byte. +// Returns a valid pointer on success or NULL on error. +// If an error occurs, negative ERRNO values will be written to error_code. +shm_struct_t *open_lock_shm(char *path, uint32_t num_locks, int *error_code) { + int shm_fd; + shm_struct_t *shm; + size_t shm_size; + uint32_t num_bitmaps; + + if (error_code == NULL) { + return NULL; + } + + // We need a nonzero number of locks + if (num_locks == 0) { + *error_code = -1 * EINVAL; + return NULL; + } + + if (path == NULL) { + *error_code = -1 * EINVAL; + return NULL; + } + + // Calculate the number of bitmaps required + num_bitmaps = num_locks / BITMAP_SIZE; + if (num_locks % BITMAP_SIZE != 0) { + num_bitmaps += 1; + } + + // Calculate size of the shm segment + shm_size = compute_shm_size(num_bitmaps); + + shm_fd = shm_open(path, O_RDWR, 0600); + if (shm_fd < 0) { + *error_code = -1 * errno; + return NULL; + } + + // Map the shared memory in + shm = mmap(NULL, shm_size, PROT_READ | PROT_WRITE, MAP_SHARED, shm_fd, 0); + if (shm == MAP_FAILED) { + *error_code = -1 * errno; + } + + // Ignore errors, it's ok if we leak a single FD since this only runs once + close(shm_fd); + + // Check if we successfully mmap'd + if (shm == MAP_FAILED) { + return NULL; + } + + // Need to check the SHM to see if it's actually our locks + if (shm->magic != MAGIC) { + *error_code = -1 * errno; + goto CLEANUP; + } + if (shm->num_locks != (num_bitmaps * BITMAP_SIZE)) { + *error_code = -1 * errno; + goto CLEANUP; + } + + return shm; + + CLEANUP: + munmap(shm, shm_size); + return NULL; +} + +// Close an open SHM lock struct, unmapping the backing memory. +// The given shm_struct_t will be rendered unusable as a result. +// On success, 0 is returned. On failure, negative ERRNO values are returned. +int32_t close_lock_shm(shm_struct_t *shm) { + int ret_code; + size_t shm_size; + + // We can't unmap null... + if (shm == NULL) { + return -1 * EINVAL; + } + + shm_size = compute_shm_size(shm->num_bitmaps); + + ret_code = munmap(shm, shm_size); + + if (ret_code != 0) { + return -1 * errno; + } + + return 0; +} + +// Allocate the first available semaphore +// Returns a positive integer guaranteed to be less than UINT32_MAX on success, +// or negative errno values on failure +// On sucess, the returned integer is the number of the semaphore allocated +int64_t allocate_semaphore(shm_struct_t *shm) { + int ret_code, i; + bitmap_t test_map; + int64_t sem_number, num_within_bitmap; + + if (shm == NULL) { + return -1 * EINVAL; + } + + // Lock the semaphore controlling access to our shared memory + ret_code = take_mutex(&(shm->segment_lock)); + if (ret_code != 0) { + return -1 * ret_code; + } + + // Loop through our bitmaps to search for one that is not full + for (i = 0; i < shm->num_bitmaps; i++) { + if (shm->locks[i].bitmap != 0xFFFFFFFF) { + test_map = 0x1; + num_within_bitmap = 0; + while (test_map != 0) { + if ((test_map & shm->locks[i].bitmap) == 0) { + // Compute the number of the semaphore we are allocating + sem_number = (BITMAP_SIZE * i) + num_within_bitmap; + // OR in the bitmap + shm->locks[i].bitmap = shm->locks[i].bitmap | test_map; + + // Clear the mutex + ret_code = release_mutex(&(shm->segment_lock)); + if (ret_code != 0) { + return -1 * ret_code; + } + + // Return the semaphore we've allocated + return sem_number; + } + test_map = test_map << 1; + num_within_bitmap++; + } + // We should never fall through this loop + // TODO maybe an assert() here to panic if we do? + } + } + + // Clear the mutex + ret_code = release_mutex(&(shm->segment_lock)); + if (ret_code != 0) { + return -1 * ret_code; + } + + // All bitmaps are full + // We have no available semaphores, report allocation failure + return -1 * ENOSPC; +} + +// Deallocate a given semaphore +// Returns 0 on success, negative ERRNO values on failure +int32_t deallocate_semaphore(shm_struct_t *shm, uint32_t sem_index) { + bitmap_t test_map; + int bitmap_index, index_in_bitmap, ret_code, i; + + if (shm == NULL) { + return -1 * EINVAL; + } + + // Check if the lock index is valid + if (sem_index >= shm->num_locks) { + return -1 * EINVAL; + } + + bitmap_index = sem_index / BITMAP_SIZE; + index_in_bitmap = sem_index % BITMAP_SIZE; + + // This should never happen if the sem_index test above succeeded, but better + // safe than sorry + if (bitmap_index >= shm->num_bitmaps) { + return -1 * EFAULT; + } + + test_map = 0x1 << index_in_bitmap; + + // Lock the mutex controlling access to our shared memory + ret_code = take_mutex(&(shm->segment_lock)); + if (ret_code != 0) { + return -1 * ret_code; + } + + // Check if the semaphore is allocated + if ((test_map & shm->locks[bitmap_index].bitmap) == 0) { + ret_code = release_mutex(&(shm->segment_lock)); + if (ret_code != 0) { + return -1 * ret_code; + } + + return -1 * ENOENT; + } + + // The semaphore is allocated, clear it + // Invert the bitmask we used to test to clear the bit + test_map = ~test_map; + shm->locks[bitmap_index].bitmap = shm->locks[bitmap_index].bitmap & test_map; + + ret_code = release_mutex(&(shm->segment_lock)); + if (ret_code != 0) { + return -1 * ret_code; + } + + return 0; +} + +// Lock a given semaphore +// Does not check if the semaphore is allocated - this ensures that, even for +// removed containers, we can still successfully lock to check status (and +// subsequently realize they have been removed). +// Returns 0 on success, -1 on failure +int32_t lock_semaphore(shm_struct_t *shm, uint32_t sem_index) { + int bitmap_index, index_in_bitmap, ret_code; + + if (shm == NULL) { + return -1 * EINVAL; + } + + if (sem_index >= shm->num_locks) { + return -1 * EINVAL; + } + + bitmap_index = sem_index / BITMAP_SIZE; + index_in_bitmap = sem_index % BITMAP_SIZE; + + return -1 * take_mutex(&(shm->locks[bitmap_index].locks[index_in_bitmap])); +} + +// Unlock a given semaphore +// Does not check if the semaphore is allocated - this ensures that, even for +// removed containers, we can still successfully lock to check status (and +// subsequently realize they have been removed). +// Returns 0 on success, -1 on failure +int32_t unlock_semaphore(shm_struct_t *shm, uint32_t sem_index) { + int bitmap_index, index_in_bitmap, ret_code; + + if (shm == NULL) { + return -1 * EINVAL; + } + + if (sem_index >= shm->num_locks) { + return -1 * EINVAL; + } + + bitmap_index = sem_index / BITMAP_SIZE; + index_in_bitmap = sem_index % BITMAP_SIZE; + + return -1 * release_mutex(&(shm->locks[bitmap_index].locks[index_in_bitmap])); +} diff --git a/libpod/lock/shm/shm_lock.go b/libpod/lock/shm/shm_lock.go new file mode 100644 index 000000000..87d28e5c1 --- /dev/null +++ b/libpod/lock/shm/shm_lock.go @@ -0,0 +1,216 @@ +package shm + +// #cgo LDFLAGS: -lrt -lpthread +// #include <stdlib.h> +// #include "shm_lock.h" +// const uint32_t bitmap_size_c = BITMAP_SIZE; +import "C" + +import ( + "runtime" + "syscall" + "unsafe" + + "github.com/pkg/errors" + "github.com/sirupsen/logrus" +) + +var ( + // BitmapSize is the size of the bitmap used when managing SHM locks. + // an SHM lock manager's max locks will be rounded up to a multiple of + // this number. + BitmapSize uint32 = uint32(C.bitmap_size_c) +) + +// SHMLocks is a struct enabling POSIX semaphore locking in a shared memory +// segment. +type SHMLocks struct { // nolint + lockStruct *C.shm_struct_t + maxLocks uint32 + valid bool +} + +// CreateSHMLock sets up a shared-memory segment holding a given number of POSIX +// semaphores, and returns a struct that can be used to operate on those locks. +// numLocks must not be 0, and may be rounded up to a multiple of the bitmap +// size used by the underlying implementation. +func CreateSHMLock(path string, numLocks uint32) (*SHMLocks, error) { + if numLocks == 0 { + return nil, errors.Wrapf(syscall.EINVAL, "number of locks must be greater than 0") + } + + locks := new(SHMLocks) + + cPath := C.CString(path) + defer C.free(unsafe.Pointer(cPath)) + + var errCode C.int + lockStruct := C.setup_lock_shm(cPath, C.uint32_t(numLocks), &errCode) + if lockStruct == nil { + // We got a null pointer, so something errored + return nil, errors.Wrapf(syscall.Errno(-1*errCode), "failed to create %d locks in %s", numLocks, path) + } + + locks.lockStruct = lockStruct + locks.maxLocks = uint32(lockStruct.num_locks) + locks.valid = true + + logrus.Debugf("Initialized SHM lock manager at path %s", path) + + return locks, nil +} + +// OpenSHMLock opens an existing shared-memory segment holding a given number of +// POSIX semaphores. numLocks must match the number of locks the shared memory +// segment was created with. +func OpenSHMLock(path string, numLocks uint32) (*SHMLocks, error) { + if numLocks == 0 { + return nil, errors.Wrapf(syscall.EINVAL, "number of locks must be greater than 0") + } + + locks := new(SHMLocks) + + cPath := C.CString(path) + defer C.free(unsafe.Pointer(cPath)) + + var errCode C.int + lockStruct := C.open_lock_shm(cPath, C.uint32_t(numLocks), &errCode) + if lockStruct == nil { + // We got a null pointer, so something errored + return nil, errors.Wrapf(syscall.Errno(-1*errCode), "failed to open %d locks in %s", numLocks, path) + } + + locks.lockStruct = lockStruct + locks.maxLocks = numLocks + locks.valid = true + + return locks, nil +} + +// GetMaxLocks returns the maximum number of locks in the SHM +func (locks *SHMLocks) GetMaxLocks() uint32 { + return locks.maxLocks +} + +// Close closes an existing shared-memory segment. +// The segment will be rendered unusable after closing. +// WARNING: If you Close() while there are still locks locked, these locks may +// fail to release, causing a program freeze. +// Close() is only intended to be used while testing the locks. +func (locks *SHMLocks) Close() error { + if !locks.valid { + return errors.Wrapf(syscall.EINVAL, "locks have already been closed") + } + + locks.valid = false + + retCode := C.close_lock_shm(locks.lockStruct) + if retCode < 0 { + // Negative errno returned + return syscall.Errno(-1 * retCode) + } + + return nil +} + +// AllocateSemaphore allocates a semaphore from a shared-memory segment for use +// by a container or pod. +// Returns the index of the semaphore that was allocated. +// Allocations past the maximum number of locks given when the SHM segment was +// created will result in an error, and no semaphore will be allocated. +func (locks *SHMLocks) AllocateSemaphore() (uint32, error) { + if !locks.valid { + return 0, errors.Wrapf(syscall.EINVAL, "locks have already been closed") + } + + // This returns a U64, so we have the full u32 range available for + // semaphore indexes, and can still return error codes. + retCode := C.allocate_semaphore(locks.lockStruct) + if retCode < 0 { + // Negative errno returned + return 0, syscall.Errno(-1 * retCode) + } + + return uint32(retCode), nil +} + +// DeallocateSemaphore frees a semaphore in a shared-memory segment so it can be +// reallocated to another container or pod. +// The given semaphore must be already allocated, or an error will be returned. +func (locks *SHMLocks) DeallocateSemaphore(sem uint32) error { + if !locks.valid { + return errors.Wrapf(syscall.EINVAL, "locks have already been closed") + } + + if sem > locks.maxLocks { + return errors.Wrapf(syscall.EINVAL, "given semaphore %d is higher than maximum locks count %d", sem, locks.maxLocks) + } + + retCode := C.deallocate_semaphore(locks.lockStruct, C.uint32_t(sem)) + if retCode < 0 { + // Negative errno returned + return syscall.Errno(-1 * retCode) + } + + return nil +} + +// LockSemaphore locks the given semaphore. +// If the semaphore is already locked, LockSemaphore will block until the lock +// can be acquired. +// There is no requirement that the given semaphore be allocated. +// This ensures that attempts to lock a container after it has been deleted, +// but before the caller has queried the database to determine this, will +// succeed. +func (locks *SHMLocks) LockSemaphore(sem uint32) error { + if !locks.valid { + return errors.Wrapf(syscall.EINVAL, "locks have already been closed") + } + + if sem > locks.maxLocks { + return errors.Wrapf(syscall.EINVAL, "given semaphore %d is higher than maximum locks count %d", sem, locks.maxLocks) + } + + // For pthread mutexes, we have to guarantee lock and unlock happen in + // the same thread. + runtime.LockOSThread() + + retCode := C.lock_semaphore(locks.lockStruct, C.uint32_t(sem)) + if retCode < 0 { + // Negative errno returned + return syscall.Errno(-1 * retCode) + } + + return nil +} + +// UnlockSemaphore unlocks the given semaphore. +// Unlocking a semaphore that is already unlocked with return EBUSY. +// There is no requirement that the given semaphore be allocated. +// This ensures that attempts to lock a container after it has been deleted, +// but before the caller has queried the database to determine this, will +// succeed. +func (locks *SHMLocks) UnlockSemaphore(sem uint32) error { + if !locks.valid { + return errors.Wrapf(syscall.EINVAL, "locks have already been closed") + } + + if sem > locks.maxLocks { + return errors.Wrapf(syscall.EINVAL, "given semaphore %d is higher than maximum locks count %d", sem, locks.maxLocks) + } + + retCode := C.unlock_semaphore(locks.lockStruct, C.uint32_t(sem)) + if retCode < 0 { + // Negative errno returned + return syscall.Errno(-1 * retCode) + } + + // For pthread mutexes, we have to guarantee lock and unlock happen in + // the same thread. + // OK if we take multiple locks - UnlockOSThread() won't actually unlock + // until the number of calls equals the number of calls to + // LockOSThread() + runtime.UnlockOSThread() + + return nil +} diff --git a/libpod/lock/shm/shm_lock.h b/libpod/lock/shm/shm_lock.h new file mode 100644 index 000000000..8e7e23fb7 --- /dev/null +++ b/libpod/lock/shm/shm_lock.h @@ -0,0 +1,46 @@ +#ifndef shm_locks_h_ +#define shm_locks_h_ + +#include <pthread.h> +#include <stdint.h> + +// Magic number to ensure we open the right SHM segment +#define MAGIC 0x87D1 + +// Type for our bitmaps +typedef uint32_t bitmap_t; + +// bitmap size +#define BITMAP_SIZE (sizeof(bitmap_t) * 8) + +// Struct to hold a single bitmap and associated locks +typedef struct lock_group { + bitmap_t bitmap; + pthread_mutex_t locks[BITMAP_SIZE]; +} lock_group_t; + +// Struct to hold our SHM locks. +// Unused is required to be 0 in the current implementation. If we ever make +// changes to this structure in the future, this will be repurposed as a version +// field. +typedef struct shm_struct { + uint16_t magic; + uint16_t unused; + pthread_mutex_t segment_lock; + uint32_t num_bitmaps; + uint32_t num_locks; + lock_group_t locks[]; +} shm_struct_t; + +static size_t compute_shm_size(uint32_t num_bitmaps); +static int take_mutex(pthread_mutex_t *mutex); +static int release_mutex(pthread_mutex_t *mutex); +shm_struct_t *setup_lock_shm(char *path, uint32_t num_locks, int *error_code); +shm_struct_t *open_lock_shm(char *path, uint32_t num_locks, int *error_code); +int32_t close_lock_shm(shm_struct_t *shm); +int64_t allocate_semaphore(shm_struct_t *shm); +int32_t deallocate_semaphore(shm_struct_t *shm, uint32_t sem_index); +int32_t lock_semaphore(shm_struct_t *shm, uint32_t sem_index); +int32_t unlock_semaphore(shm_struct_t *shm, uint32_t sem_index); + +#endif diff --git a/libpod/lock/shm/shm_lock_test.go b/libpod/lock/shm/shm_lock_test.go new file mode 100644 index 000000000..594eb5d8e --- /dev/null +++ b/libpod/lock/shm/shm_lock_test.go @@ -0,0 +1,278 @@ +package shm + +import ( + "fmt" + "os" + "runtime" + "syscall" + "testing" + "time" + + "github.com/stretchr/testify/assert" + "github.com/stretchr/testify/require" +) + +// All tests here are in the same process, which somewhat limits their utility +// The big intent of this package it multiprocess locking, which is really hard +// to test without actually having multiple processes... +// We can at least verify that the locks work within the local process. + +var ( + // 4 * BITMAP_SIZE to ensure we have to traverse bitmaps + numLocks = 4 * BitmapSize +) + +const lockPath = "/libpod_test" + +// We need a test main to ensure that the SHM is created before the tests run +func TestMain(m *testing.M) { + shmLock, err := CreateSHMLock(lockPath, numLocks) + if err != nil { + fmt.Fprintf(os.Stderr, "Error creating SHM for tests: %v\n", err) + os.Exit(-1) + } + + // Close the SHM - every subsequent test will reopen + if err := shmLock.Close(); err != nil { + fmt.Fprintf(os.Stderr, "Error closing SHM locks: %v\n", err) + os.Exit(-1) + } + + exitCode := m.Run() + + // We need to remove the SHM segment to clean up after ourselves + os.RemoveAll("/dev/shm/libpod_lock") + + os.Exit(exitCode) +} + +func runLockTest(t *testing.T, testFunc func(*testing.T, *SHMLocks)) { + locks, err := OpenSHMLock(lockPath, numLocks) + if err != nil { + t.Fatalf("Error opening locks: %v", err) + } + defer func() { + // Deallocate all locks + // Ignore ENOENT (lock is not allocated) + var i uint32 + for i = 0; i < numLocks; i++ { + if err := locks.DeallocateSemaphore(i); err != nil && err != syscall.ENOENT { + t.Fatalf("Error deallocating semaphore %d: %v", i, err) + } + } + + if err := locks.Close(); err != nil { + t.Fatalf("Error closing locks: %v", err) + } + }() + + success := t.Run("locks", func(t *testing.T) { + testFunc(t, locks) + }) + if !success { + t.Fail() + } +} + +// Test that creating an SHM with a bad size rounds up to a good size +func TestCreateNewSHMBadSizeRoundsUp(t *testing.T) { + // Odd number, not a power of 2, should never be a word size on a system + lock, err := CreateSHMLock("/test1", 7) + assert.NoError(t, err) + + assert.Equal(t, lock.GetMaxLocks(), BitmapSize) + + if err := lock.Close(); err != nil { + t.Fatalf("Error closing locks: %v", err) + } +} + +// Test that creating an SHM with 0 size fails +func TestCreateNewSHMZeroSize(t *testing.T) { + _, err := CreateSHMLock("/test2", 0) + assert.Error(t, err) +} + +// Test that deallocating an unallocated lock errors +func TestDeallocateUnallocatedLockErrors(t *testing.T) { + runLockTest(t, func(t *testing.T, locks *SHMLocks) { + err := locks.DeallocateSemaphore(0) + assert.Error(t, err) + }) +} + +// Test that unlocking an unlocked lock fails +func TestUnlockingUnlockedLockFails(t *testing.T) { + runLockTest(t, func(t *testing.T, locks *SHMLocks) { + err := locks.UnlockSemaphore(0) + assert.Error(t, err) + }) +} + +// Test that locking and double-unlocking fails +func TestDoubleUnlockFails(t *testing.T) { + runLockTest(t, func(t *testing.T, locks *SHMLocks) { + err := locks.LockSemaphore(0) + assert.NoError(t, err) + + err = locks.UnlockSemaphore(0) + assert.NoError(t, err) + + err = locks.UnlockSemaphore(0) + assert.Error(t, err) + }) +} + +// Test allocating - lock - unlock - deallocate cycle, single lock +func TestLockLifecycleSingleLock(t *testing.T) { + runLockTest(t, func(t *testing.T, locks *SHMLocks) { + sem, err := locks.AllocateSemaphore() + require.NoError(t, err) + + err = locks.LockSemaphore(sem) + assert.NoError(t, err) + + err = locks.UnlockSemaphore(sem) + assert.NoError(t, err) + + err = locks.DeallocateSemaphore(sem) + assert.NoError(t, err) + }) +} + +// Test allocate two locks returns different locks +func TestAllocateTwoLocksGetsDifferentLocks(t *testing.T) { + runLockTest(t, func(t *testing.T, locks *SHMLocks) { + sem1, err := locks.AllocateSemaphore() + assert.NoError(t, err) + + sem2, err := locks.AllocateSemaphore() + assert.NoError(t, err) + + assert.NotEqual(t, sem1, sem2) + }) +} + +// Test allocate all locks successful and all are unique +func TestAllocateAllLocksSucceeds(t *testing.T) { + runLockTest(t, func(t *testing.T, locks *SHMLocks) { + sems := make(map[uint32]bool) + var i uint32 + for i = 0; i < numLocks; i++ { + sem, err := locks.AllocateSemaphore() + assert.NoError(t, err) + + // Ensure the allocate semaphore is unique + _, ok := sems[sem] + assert.False(t, ok) + + sems[sem] = true + } + }) +} + +// Test allocating more than the given max fails +func TestAllocateTooManyLocksFails(t *testing.T) { + runLockTest(t, func(t *testing.T, locks *SHMLocks) { + // Allocate all locks + var i uint32 + for i = 0; i < numLocks; i++ { + _, err := locks.AllocateSemaphore() + assert.NoError(t, err) + } + + // Try and allocate one more + _, err := locks.AllocateSemaphore() + assert.Error(t, err) + }) +} + +// Test allocating max locks, deallocating one, and then allocating again succeeds +func TestAllocateDeallocateCycle(t *testing.T) { + runLockTest(t, func(t *testing.T, locks *SHMLocks) { + // Allocate all locks + var i uint32 + for i = 0; i < numLocks; i++ { + _, err := locks.AllocateSemaphore() + assert.NoError(t, err) + } + + // Now loop through again, deallocating and reallocating. + // Each time we free 1 semaphore, allocate again, and make sure + // we get the same semaphore back. + var j uint32 + for j = 0; j < numLocks; j++ { + err := locks.DeallocateSemaphore(j) + assert.NoError(t, err) + + newSem, err := locks.AllocateSemaphore() + assert.NoError(t, err) + assert.Equal(t, j, newSem) + } + }) +} + +// Test that locks actually lock +func TestLockSemaphoreActuallyLocks(t *testing.T) { + runLockTest(t, func(t *testing.T, locks *SHMLocks) { + // This entire test is very ugly - lots of sleeps to try and get + // things to occur in the right order. + // It also doesn't even exercise the multiprocess nature of the + // locks. + + // Get the current time + startTime := time.Now() + + // Start a goroutine to take the lock and then release it after + // a second. + go func() { + err := locks.LockSemaphore(0) + assert.NoError(t, err) + + time.Sleep(1 * time.Second) + + err = locks.UnlockSemaphore(0) + assert.NoError(t, err) + }() + + // Sleep for a quarter of a second to give the goroutine time + // to kick off and grab the lock + time.Sleep(250 * time.Millisecond) + + // Take the lock + err := locks.LockSemaphore(0) + assert.NoError(t, err) + + // Get the current time + endTime := time.Now() + + // Verify that at least 1 second has passed since start + duration := endTime.Sub(startTime) + assert.True(t, duration.Seconds() > 1.0) + }) +} + +// Test that locking and unlocking two semaphores succeeds +// Ensures that runtime.LockOSThread() is doing its job +func TestLockAndUnlockTwoSemaphore(t *testing.T) { + runLockTest(t, func(t *testing.T, locks *SHMLocks) { + err := locks.LockSemaphore(5) + assert.NoError(t, err) + + err = locks.LockSemaphore(6) + assert.NoError(t, err) + + err = locks.UnlockSemaphore(6) + assert.NoError(t, err) + + // Now yield scheduling + // To try and get us on another OS thread + runtime.Gosched() + + // And unlock the last semaphore + // If we are in a different OS thread, this should fail. + // However, runtime.UnlockOSThread() should guarantee we are not + err = locks.UnlockSemaphore(5) + assert.NoError(t, err) + }) +} |