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Move to POSIX mutexes for SHM locks

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Signed-off-by: Matthew Heon <matthew.heon@gmail.com>
This commit is contained in:
Matthew Heon
2018-08-10 13:46:07 -04:00
committed by Matthew Heon
parent f38fccb48c
commit e73484c176
6 changed files with 271 additions and 171 deletions
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8
libpod/lock/lock.go
View File

@ -23,7 +23,7 @@ type Manager interface {
// RetrieveLock retrieves a lock given its UUID.
// The underlying lock MUST be the same as another other lock with the
// same UUID.
RetrieveLock(id string) (Locker, error)
RetrieveLock(id uint32) (Locker, error)
}
// Locker is similar to sync.Locker, but provides a method for freeing the lock
@ -37,7 +37,7 @@ type Locker interface {
// ID is guaranteed to uniquely identify the lock within the
// Manager - that is, calling RetrieveLock with this ID will return
// another instance of the same lock.
ID() string
ID() uint32
// Lock locks the lock.
// This call MUST block until it successfully acquires the lock or
// encounters a fatal error.
@ -46,8 +46,8 @@ type Locker interface {
// A call to Unlock() on a lock that is already unlocked lock MUST
// error.
Unlock() error
// Deallocate deallocates the underlying lock, allowing its reuse by
// other pods and containers.
// Free deallocates the underlying lock, allowing its reuse by other
// pods and containers.
// The lock MUST still be usable after a Free() - some libpod instances
// may still retain Container structs with the old lock. This simply
// advises the manager that the lock may be reallocated.

249
libpod/lock/shm/shm_lock.c
View File

@ -1,6 +1,6 @@
#include <errno.h>
#include <fcntl.h>
#include <semaphore.h>
#include <pthread.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdlib.h>
@ -12,19 +12,67 @@
#include "shm_lock.h"
// Compute the size of the SHM struct
size_t compute_shm_size(uint32_t num_bitmaps) {
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 be a multiple of BITMAP_SIZE (32 by default).
// 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, it will be written to the int pointed to by error_code.
shm_struct_t *setup_lock_shm(uint32_t num_locks, int *error_code) {
// 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
@ -34,67 +82,93 @@ shm_struct_t *setup_lock_shm(uint32_t num_locks, int *error_code) {
// We need a nonzero number of locks
if (num_locks == 0) {
*error_code = EINVAL;
*error_code = -1 * EINVAL;
return NULL;
}
if (path == NULL) {
*error_code = -1 * EINVAL;
return NULL;
}
// Calculate the number of bitmaps required
if (num_locks % BITMAP_SIZE != 0) {
// Number of locks not a multiple of BITMAP_SIZE
*error_code = EINVAL;
return NULL;
}
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(SHM_NAME, O_RDWR | O_CREAT | O_EXCL, 0600);
shm_fd = shm_open(path, O_RDWR | O_CREAT | O_EXCL, 0600);
if (shm_fd < 0) {
*error_code = errno;
*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 = errno;
*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 = errno;
*error_code = -1 * errno;
goto CLEANUP_UNLINK;
}
// We have successfully mapped the memory, now initialize the region
shm->magic = MAGIC;
shm->num_locks = num_locks;
shm->unused = 0;
shm->num_locks = num_bitmaps * BITMAP_SIZE;
shm->num_bitmaps = num_bitmaps;
// Initialize the semaphore that protects the bitmaps.
// Initialize to value 1, as we're a mutex, and set pshared as this will be
// shared between processes in an SHM.
ret_code = sem_init(&(shm->segment_lock), true, 1);
if (ret_code < 0) {
*error_code = errno;
// 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++) {
// As above, initialize to 1 to act as a mutex, and set pshared as we'll
// be living in an SHM.
ret_code = sem_init(&(shm->locks[i].locks[j]), true, 1);
if (ret_code < 0) {
*error_code = errno;
goto CLEANUP_UNMAP;
// 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;
}
}
}
@ -103,23 +177,33 @@ shm_struct_t *setup_lock_shm(uint32_t num_locks, int *error_code) {
// 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(SHM_NAME);
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 must be a multiple of BITMAP_SIZE (32 by default).
// 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, it will be written to the int pointed to by error_code.
shm_struct_t *open_lock_shm(uint32_t num_locks, int *error_code) {
// 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;
@ -131,30 +215,34 @@ shm_struct_t *open_lock_shm(uint32_t num_locks, int *error_code) {
// We need a nonzero number of locks
if (num_locks == 0) {
*error_code = EINVAL;
*error_code = -1 * EINVAL;
return NULL;
}
if (path == NULL) {
*error_code = -1 * EINVAL;
return NULL;
}
// Calculate the number of bitmaps required
if (num_locks % BITMAP_SIZE != 0) {
// Number of locks not a multiple of BITMAP_SIZE
*error_code = EINVAL;
return NULL;
}
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(SHM_NAME, O_RDWR, 0600);
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 = errno;
*error_code = -1 * errno;
}
// Ignore errors, it's ok if we leak a single FD since this only runs once
@ -167,11 +255,11 @@ shm_struct_t *open_lock_shm(uint32_t num_locks, int *error_code) {
// Need to check the SHM to see if it's actually our locks
if (shm->magic != MAGIC) {
*error_code = errno;
*error_code = -1 * errno;
goto CLEANUP;
}
if (shm->num_locks != num_locks) {
*error_code = errno;
if (shm->num_locks != (num_bitmaps * BITMAP_SIZE)) {
*error_code = -1 * errno;
goto CLEANUP;
}
@ -219,11 +307,9 @@ int64_t allocate_semaphore(shm_struct_t *shm) {
}
// Lock the semaphore controlling access to our shared memory
do {
ret_code = sem_wait(&(shm->segment_lock));
} while(ret_code == EINTR);
ret_code = take_mutex(&(shm->segment_lock));
if (ret_code != 0) {
return -1 * errno;
return -1 * ret_code;
}
// Loop through our bitmaps to search for one that is not full
@ -237,8 +323,13 @@ int64_t allocate_semaphore(shm_struct_t *shm) {
sem_number = (BITMAP_SIZE * i) + num_within_bitmap;
// OR in the bitmap
shm->locks[i].bitmap = shm->locks[i].bitmap | test_map;
// Clear the semaphore
sem_post(&(shm->segment_lock));
// 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;
}
@ -250,8 +341,11 @@ int64_t allocate_semaphore(shm_struct_t *shm) {
}
}
// Post to the semaphore to clear the lock
sem_post(&(shm->segment_lock));
// 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
@ -282,23 +376,20 @@ int32_t deallocate_semaphore(shm_struct_t *shm, uint32_t sem_index) {
return -1 * EFAULT;
}
test_map = 0x1;
for (i = 0; i < index_in_bitmap; i++) {
test_map = test_map << 1;
}
test_map = 0x1 << index_in_bitmap;
// Lock the semaphore controlling access to our shared memory
do {
ret_code = sem_wait(&(shm->segment_lock));
} while(ret_code == EINTR);
// Lock the mutex controlling access to our shared memory
ret_code = take_mutex(&(shm->segment_lock));
if (ret_code != 0) {
return -1 * errno;
return -1 * ret_code;
}
// Check if the semaphore is allocated
if ((test_map & shm->locks[bitmap_index].bitmap) == 0) {
// Post to the semaphore to clear the lock
sem_post(&(shm->segment_lock));
ret_code = release_mutex(&(shm->segment_lock));
if (ret_code != 0) {
return -1 * ret_code;
}
return -1 * ENOENT;
}
@ -308,8 +399,10 @@ int32_t deallocate_semaphore(shm_struct_t *shm, uint32_t sem_index) {
test_map = ~test_map;
shm->locks[bitmap_index].bitmap = shm->locks[bitmap_index].bitmap & test_map;
// Post to the semaphore to clear the lock
sem_post(&(shm->segment_lock));
ret_code = release_mutex(&(shm->segment_lock));
if (ret_code != 0) {
return -1 * ret_code;
}
return 0;
}
@ -333,15 +426,7 @@ int32_t lock_semaphore(shm_struct_t *shm, uint32_t sem_index) {
bitmap_index = sem_index / BITMAP_SIZE;
index_in_bitmap = sem_index % BITMAP_SIZE;
// Lock the semaphore controlling access to our shared memory
do {
ret_code = sem_wait(&(shm->locks[bitmap_index].locks[index_in_bitmap]));
} while(ret_code == EINTR);
if (ret_code != 0) {
return -1 * errno;
}
return 0;
return -1 * take_mutex(&(shm->locks[bitmap_index].locks[index_in_bitmap]));
}
// Unlock a given semaphore
@ -351,7 +436,6 @@ int32_t lock_semaphore(shm_struct_t *shm, uint32_t sem_index) {
// 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;
unsigned int sem_value = 0;
if (shm == NULL) {
return -1 * EINVAL;
@ -364,20 +448,5 @@ int32_t unlock_semaphore(shm_struct_t *shm, uint32_t sem_index) {
bitmap_index = sem_index / BITMAP_SIZE;
index_in_bitmap = sem_index % BITMAP_SIZE;
// Only allow a post if the semaphore is less than 1 (locked)
// This allows us to preserve mutex behavior
ret_code = sem_getvalue(&(shm->locks[bitmap_index].locks[index_in_bitmap]), &sem_value);
if (ret_code != 0) {
return -1 * errno;
}
if (sem_value >= 1) {
return -1 * EBUSY;
}
ret_code = sem_post(&(shm->locks[bitmap_index].locks[index_in_bitmap]));
if (ret_code != 0) {
return -1 * errno;
}
return 0;
return -1 * release_mutex(&(shm->locks[bitmap_index].locks[index_in_bitmap]));
}

52
libpod/lock/shm/shm_lock.go
View File

@ -1,47 +1,54 @@
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"
)
var (
bitmapSize uint32 = uint32(C.bitmap_size_c)
const (
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
valid bool
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 be a multiple of the lock bitmap size (by default, 32).
func CreateSHMLock(numLocks uint32) (*SHMLocks, error) {
if numLocks%bitmapSize != 0 || numLocks == 0 {
return nil, errors.Wrapf(syscall.EINVAL, "number of locks must be a multiple of %d", C.bitmap_size_c)
// 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 greater than 0 0")
}
locks := new(SHMLocks)
cPath := C.CString(path)
defer C.free(unsafe.Pointer(cPath))
var errCode C.int
lockStruct := C.setup_lock_shm(C.uint32_t(numLocks), &errCode)
lockStruct := C.setup_lock_shm(cPath, C.uint32_t(numLocks), &errCode)
if lockStruct == nil {
// We got a null pointer, so something errored
return nil, syscall.Errno(-1 * errCode)
}
locks.lockStruct = lockStruct
locks.maxLocks = numLocks
locks.maxLocks = uint32(lockStruct.num_locks)
locks.valid = true
return locks, nil
@ -49,17 +56,19 @@ func CreateSHMLock(numLocks uint32) (*SHMLocks, error) {
// 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 and be a multiple of the lock bitmap size (default
// 32).
func OpenSHMLock(numLocks uint32) (*SHMLocks, error) {
if numLocks%bitmapSize != 0 || numLocks == 0 {
return nil, errors.Wrapf(syscall.EINVAL, "number of locks must be a multiple of %d", C.bitmap_size_c)
// 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 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(C.uint32_t(numLocks), &errCode)
lockStruct := C.open_lock_shm(cPath, C.uint32_t(numLocks), &errCode)
if lockStruct == nil {
// We got a null pointer, so something errored
return nil, syscall.Errno(-1 * errCode)
@ -108,6 +117,8 @@ func (locks *SHMLocks) AllocateSemaphore() (uint32, error) {
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
@ -154,6 +165,10 @@ func (locks *SHMLocks) LockSemaphore(sem uint32) error {
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
@ -184,5 +199,12 @@ func (locks *SHMLocks) UnlockSemaphore(sem uint32) error {
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
}

35
libpod/lock/shm/shm_lock.h
View File

@ -1,14 +1,11 @@
#ifndef shm_locks_h_
#define shm_locks_h_
#include <semaphore.h>
#include <pthread.h>
#include <stdint.h>
// Magic number to ensure we open the right SHM segment
#define MAGIC 0xA5A5
// Name of the SHM
#define SHM_NAME "/libpod_lock"
#define MAGIC 0x87D1
// Type for our bitmaps
typedef uint32_t bitmap_t;
@ -18,22 +15,28 @@ typedef uint32_t bitmap_t;
// Struct to hold a single bitmap and associated locks
typedef struct lock_group {
bitmap_t bitmap;
sem_t locks[BITMAP_SIZE];
bitmap_t bitmap;
pthread_mutex_t locks[BITMAP_SIZE];
} lock_group_t;
// Struct to hold our SHM locks
// 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;
sem_t segment_lock;
uint32_t num_bitmaps;
uint32_t num_locks;
lock_group_t locks[];
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;
size_t compute_shm_size(uint32_t num_bitmaps);
shm_struct_t *setup_lock_shm(uint32_t num_locks, int *error_code);
shm_struct_t *open_lock_shm(uint32_t num_locks, int *error_code);
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);

56
libpod/lock/shm/shm_lock_test.go
View File

@ -3,6 +3,7 @@ package shm
import (
"fmt"
"os"
"runtime"
"syscall"
"testing"
"time"
@ -17,11 +18,13 @@ import (
// We can at least verify that the locks work within the local process.
// 4 * BITMAP_SIZE to ensure we have to traverse bitmaps
const numLocks = 128
const numLocks uint32 = 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(numLocks)
shmLock, err := CreateSHMLock(lockPath, numLocks)
if err != nil {
fmt.Fprintf(os.Stderr, "Error creating SHM for tests: %v\n", err)
os.Exit(-1)
@ -42,19 +45,15 @@ func TestMain(m *testing.M) {
}
func runLockTest(t *testing.T, testFunc func(*testing.T, *SHMLocks)) {
locks, err := OpenSHMLock(numLocks)
locks, err := OpenSHMLock(lockPath, numLocks)
if err != nil {
t.Fatalf("Error opening locks: %v", err)
}
defer func() {
// Unlock and deallocate all locks
// Ignore EBUSY (lock is already unlocked)
// Deallocate all locks
// Ignore ENOENT (lock is not allocated)
var i uint32
for i = 0; i < numLocks; i++ {
if err := locks.UnlockSemaphore(i); err != nil && err != syscall.EBUSY {
t.Fatalf("Error unlocking semaphore %d: %v", i, err)
}
if err := locks.DeallocateSemaphore(i); err != nil && err != syscall.ENOENT {
t.Fatalf("Error deallocating semaphore %d: %v", i, err)
}
@ -73,16 +72,22 @@ func runLockTest(t *testing.T, testFunc func(*testing.T, *SHMLocks)) {
}
}
// Test that creating an SHM with a bad size fails
func TestCreateNewSHMBadSize(t *testing.T) {
// 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
_, err := CreateSHMLock(7)
assert.Error(t, err)
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(0)
_, err := CreateSHMLock("/test2", 0)
assert.Error(t, err)
}
@ -241,3 +246,28 @@ func TestLockSemaphoreActuallyLocks(t *testing.T) {
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(0)
assert.NoError(t, err)
err = locks.LockSemaphore(1)
assert.NoError(t, err)
err = locks.UnlockSemaphore(1)
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(0)
assert.NoError(t, err)
})
}

42
libpod/lock/shm_lock_manager_linux.go
View File

@ -3,13 +3,7 @@
package lock
import (
"fmt"
"math"
"strconv"
"syscall"
"github.com/pkg/errors"
"github.com/projectatomic/libpod/libpod/lock/shm"
"github.com/containers/libpod/libpod/lock/shm"
)
// SHMLockManager manages shared memory locks.
@ -18,8 +12,8 @@ type SHMLockManager struct {
}
// NewSHMLockManager makes a new SHMLockManager with the given number of locks.
func NewSHMLockManager(numLocks uint32) (Manager, error) {
locks, err := shm.CreateSHMLock(numLocks)
func NewSHMLockManager(path string, numLocks uint32) (Manager, error) {
locks, err := shm.CreateSHMLock(path, numLocks)
if err != nil {
return nil, err
}
@ -32,8 +26,8 @@ func NewSHMLockManager(numLocks uint32) (Manager, error) {
// OpenSHMLockManager opens an existing SHMLockManager with the given number of
// locks.
func OpenSHMLockManager(numLocks uint32) (Manager, error) {
locks, err := shm.OpenSHMLock(numLocks)
func OpenSHMLockManager(path string, numLocks uint32) (Manager, error) {
locks, err := shm.OpenSHMLock(path, numLocks)
if err != nil {
return nil, err
}
@ -59,27 +53,9 @@ func (m *SHMLockManager) AllocateLock() (Locker, error) {
}
// RetrieveLock retrieves a lock from the manager given its ID.
func (m *SHMLockManager) RetrieveLock(id string) (Locker, error) {
intID, err := strconv.ParseInt(id, 16, 64)
if err != nil {
return nil, errors.Wrapf(err, "given ID %q is not a valid SHMLockManager ID - cannot be parsed as int", id)
}
if intID < 0 {
return nil, errors.Wrapf(syscall.EINVAL, "given ID %q is not a valid SHMLockManager ID - must be positive", id)
}
if intID > math.MaxUint32 {
return nil, errors.Wrapf(syscall.EINVAL, "given ID %q is not a valid SHMLockManager ID - too large", id)
}
var u32ID uint32 = uint32(intID)
if u32ID >= m.locks.GetMaxLocks() {
return nil, errors.Wrapf(syscall.EINVAL, "given ID %q is not a valid SHMLockManager ID - too large to fit", id)
}
func (m *SHMLockManager) RetrieveLock(id uint32) (Locker, error) {
lock := new(SHMLock)
lock.lockID = u32ID
lock.lockID = id
lock.manager = m
return lock, nil
@ -92,8 +68,8 @@ type SHMLock struct {
}
// ID returns the ID of the lock.
func (l *SHMLock) ID() string {
return fmt.Sprintf("%x", l.lockID)
func (l *SHMLock) ID() uint32 {
return l.lockID
}
// Lock acquires the lock.