diff options
Diffstat (limited to 'libpod/lock')
| -rw-r--r-- | libpod/lock/locks.go | 26 | ||||
| -rw-r--r-- | libpod/lock/locks_test.go | 97 |
2 files changed, 117 insertions, 6 deletions
diff --git a/libpod/lock/locks.go b/libpod/lock/locks.go index c61bd78d2..4d7c26aa2 100644 --- a/libpod/lock/locks.go +++ b/libpod/lock/locks.go @@ -50,7 +50,7 @@ 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) +// 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) @@ -95,7 +95,9 @@ func (locks *SHMLocks) Close() error { // 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 +// 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") @@ -110,8 +112,9 @@ func (locks *SHMLocks) AllocateSemaphore() (uint32, error) { return uint32(retCode), nil } -// DeallocateSemaphore frees a semaphore in a shared-memory segment for use by -// a container of pod +// 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") @@ -130,7 +133,13 @@ func (locks *SHMLocks) DeallocateSemaphore(sem uint32) error { return nil } -// LockSemaphore locks the given semaphore +// 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") @@ -149,7 +158,12 @@ func (locks *SHMLocks) LockSemaphore(sem uint32) error { return nil } -// UnlockSemaphore locks the given semaphore +// 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") diff --git a/libpod/lock/locks_test.go b/libpod/lock/locks_test.go index 62a36c5da..6d4525f6a 100644 --- a/libpod/lock/locks_test.go +++ b/libpod/lock/locks_test.go @@ -4,6 +4,7 @@ import ( "fmt" "os" "syscall" + "time" "testing" "github.com/stretchr/testify/assert" @@ -145,3 +146,99 @@ func TestAllocateTwoLocksGetsDifferentLocks(t *testing.T) { 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) + 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 + 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 + 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) + }) +} |