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Merge pull request #10651 from laurazard/shim-refactor-without-pending

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runc-shim: fix races/prevent init exits from being dropped
This commit is contained in:
Samuel Karp 2024-09-05 19:10:42 +00:00 committed by GitHub
commit c8b095f3c2
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GPG Key ID: B5690EEEBB952194
1 changed files with 110 additions and 78 deletions
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188
cmd/containerd-shim-runc-v2/task/service.go
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@ -74,15 +74,17 @@ func NewTaskService(ctx context.Context, publisher shim.Publisher, sd shutdown.S
}
go ep.Run(ctx)
s := &service{
context: ctx,
events: make(chan interface{}, 128),
ec: reaper.Default.Subscribe(),
ep: ep,
shutdown: sd,
containers: make(map[string]*runc.Container),
running: make(map[int][]containerProcess),
pendingExecs: make(map[*runc.Container]int),
exitSubscribers: make(map[*map[int][]runcC.Exit]struct{}),
context: ctx,
events: make(chan interface{}, 128),
ec: reaper.Default.Subscribe(),
ep: ep,
shutdown: sd,
containers: make(map[string]*runc.Container),
running: make(map[int][]containerProcess),
runningExecs: make(map[*runc.Container]int),
execCountSubscribers: make(map[*runc.Container]chan<- int),
containerInitExit: make(map[*runc.Container]runcC.Exit),
exitSubscribers: make(map[*map[int][]runcC.Exit]struct{}),
}
go s.processExits()
runcC.Monitor = reaper.Default
@ -117,7 +119,19 @@ type service struct {
lifecycleMu sync.Mutex
running map[int][]containerProcess // pid -> running process, guarded by lifecycleMu
pendingExecs map[*runc.Container]int // container -> num pending execs, guarded by lifecycleMu
runningExecs map[*runc.Container]int // container -> num running execs, guarded by lifecycleMu
// container -> subscription to exec exits/changes to s.runningExecs[container],
// guarded by lifecycleMu
execCountSubscribers map[*runc.Container]chan<- int
// container -> init exits, guarded by lifecycleMu
// Used to stash container init process exits, so that we can hold them
// until after we've made sure to publish all the container's exec exits.
// Also used to prevent starting new execs from being started if the
// container's init process (read: pid, not [process.Init]) has already been
// reaped by the shim.
// Note that this flag gets updated before the container's [process.Init.Status]
// is transitioned to "stopped".
containerInitExit map[*runc.Container]runcC.Exit
// Subscriptions to exits for PIDs. Adding/deleting subscriptions and
// dereferencing the subscription pointers must only be done while holding
// lifecycleMu.
@ -138,8 +152,7 @@ type containerProcess struct {
//
// The returned handleStarted closure records that the process has started so
// that its exit can be handled efficiently. If the process has already exited,
// it handles the exit immediately. In addition, if the process is an exec and
// its container's init process has already exited, that exit is also processed.
// it handles the exit immediately.
// handleStarted should be called after the event announcing the start of the
// process has been published. Note that s.lifecycleMu must not be held when
// calling handleStarted.
@ -174,44 +187,8 @@ func (s *service) preStart(c *runc.Container) (handleStarted func(*runc.Containe
pid = p.Pid()
}
_, init := p.(*process.Init)
s.lifecycleMu.Lock()
var initExits []runcC.Exit
var initCps []containerProcess
if !init {
s.pendingExecs[c]--
initPid := c.Pid()
iExits, initExited := exits[initPid]
if initExited && s.pendingExecs[c] == 0 {
// c's init process has exited before handleStarted was called and
// this is the last pending exec process start - we need to process
// the exit for the init process after processing this exec, so:
// - delete c from the s.pendingExecs map
// - keep the exits for the init pid to process later (after we process
// this exec's exits)
// - get the necessary containerProcesses for the init process (that we
// need to process the exits), and remove them from s.running (which we skipped
// doing in processExits).
delete(s.pendingExecs, c)
initExits = iExits
var skipped []containerProcess
for _, initPidCp := range s.running[initPid] {
if initPidCp.Container == c {
initCps = append(initCps, initPidCp)
} else {
skipped = append(skipped, initPidCp)
}
}
if len(skipped) == 0 {
delete(s.running, initPid)
} else {
s.running[initPid] = skipped
}
}
}
ees, exited := exits[pid]
delete(s.exitSubscribers, &exits)
exits = nil
@ -220,11 +197,6 @@ func (s *service) preStart(c *runc.Container) (handleStarted func(*runc.Containe
for _, ee := range ees {
s.handleProcessExit(ee, c, p)
}
for _, eee := range initExits {
for _, cp := range initCps {
s.handleProcessExit(eee, cp.Container, cp.Process)
}
}
} else {
// Process start was successful, add to `s.running`.
s.running[pid] = append(s.running[pid], containerProcess{
@ -305,7 +277,11 @@ func (s *service) Start(ctx context.Context, r *taskAPI.StartRequest) (*taskAPI.
if r.ExecID == "" {
cinit = container
} else {
s.pendingExecs[container]++
if _, initExited := s.containerInitExit[container]; initExited {
s.lifecycleMu.Unlock()
return nil, errdefs.ToGRPCf(errdefs.ErrFailedPrecondition, "container %s init process is not running", container.ID)
}
s.runningExecs[container]++
}
handleStarted, cleanup := s.preStart(cinit)
s.lifecycleMu.Unlock()
@ -313,6 +289,17 @@ func (s *service) Start(ctx context.Context, r *taskAPI.StartRequest) (*taskAPI.
p, err := container.Start(ctx, r)
if err != nil {
// If we failed to even start the process, s.runningExecs
// won't get decremented in s.handleProcessExit. We still need
// to update it.
if r.ExecID != "" {
s.lifecycleMu.Lock()
s.runningExecs[container]--
if ch, ok := s.execCountSubscribers[container]; ok {
ch <- s.runningExecs[container]
}
s.lifecycleMu.Unlock()
}
handleStarted(container, p)
return nil, errdefs.ToGRPC(err)
}
@ -677,28 +664,23 @@ func (s *service) processExits() {
// Handle the exit for a created/started process. If there's more than
// one, assume they've all exited. One of them will be the correct
// process.
var cps, skipped []containerProcess
var cps []containerProcess
for _, cp := range s.running[e.Pid] {
_, init := cp.Process.(*process.Init)
if init && s.pendingExecs[cp.Container] != 0 {
// This exit relates to a container for which we have pending execs. In
// order to ensure order between execs and the init process for a given
// container, skip processing this exit here and let the `handleStarted`
// closure for the pending exec publish it.
skipped = append(skipped, cp)
} else {
cps = append(cps, cp)
if init {
s.containerInitExit[cp.Container] = e
}
cps = append(cps, cp)
}
if len(skipped) > 0 {
s.running[e.Pid] = skipped
} else {
delete(s.running, e.Pid)
}
delete(s.running, e.Pid)
s.lifecycleMu.Unlock()
for _, cp := range cps {
s.handleProcessExit(e, cp.Container, cp.Process)
if ip, ok := cp.Process.(*process.Init); ok {
s.handleInitExit(e, cp.Container, ip)
} else {
s.handleProcessExit(e, cp.Container, cp.Process)
}
}
}
}
@ -707,18 +689,60 @@ func (s *service) send(evt interface{}) {
s.events <- evt
}
// s.mu must be locked when calling handleProcessExit
func (s *service) handleProcessExit(e runcC.Exit, c *runc.Container, p process.Process) {
if ip, ok := p.(*process.Init); ok {
// Ensure all children are killed
if runc.ShouldKillAllOnExit(s.context, c.Bundle) {
if err := ip.KillAll(s.context); err != nil {
log.G(s.context).WithError(err).WithField("id", ip.ID()).
Error("failed to kill init's children")
}
// handleInitExit processes container init process exits.
// This is handled separately from non-init exits, because there
// are some extra invariants we want to ensure in this case, namely:
// - for a given container, the init process exit MUST be the last exit published
// This is achieved by:
// - killing all running container processes (if the container has a shared pid
// namespace, otherwise all other processes have been reaped already).
// - waiting for the container's running exec counter to reach 0.
// - finally, publishing the init exit.
func (s *service) handleInitExit(e runcC.Exit, c *runc.Container, p *process.Init) {
// kill all running container processes
if runc.ShouldKillAllOnExit(s.context, c.Bundle) {
if err := p.KillAll(s.context); err != nil {
log.G(s.context).WithError(err).WithField("id", p.ID()).
Error("failed to kill init's children")
}
}
s.lifecycleMu.Lock()
numRunningExecs := s.runningExecs[c]
if numRunningExecs == 0 {
delete(s.runningExecs, c)
s.lifecycleMu.Unlock()
s.handleProcessExit(e, c, p)
return
}
events := make(chan int, numRunningExecs)
s.execCountSubscribers[c] = events
s.lifecycleMu.Unlock()
go func() {
defer func() {
s.lifecycleMu.Lock()
defer s.lifecycleMu.Unlock()
delete(s.execCountSubscribers, c)
delete(s.runningExecs, c)
}()
// wait for running processes to exit
for {
if runningExecs := <-events; runningExecs == 0 {
break
}
}
// all running processes have exited now, and no new
// ones can start, so we can publish the init exit
s.handleProcessExit(e, c, p)
}()
}
func (s *service) handleProcessExit(e runcC.Exit, c *runc.Container, p process.Process) {
p.SetExited(e.Status)
s.send(&eventstypes.TaskExit{
ContainerID: c.ID,
@ -727,6 +751,14 @@ func (s *service) handleProcessExit(e runcC.Exit, c *runc.Container, p process.P
ExitStatus: uint32(e.Status),
ExitedAt: protobuf.ToTimestamp(p.ExitedAt()),
})
if _, init := p.(*process.Init); !init {
s.lifecycleMu.Lock()
s.runningExecs[c]--
if ch, ok := s.execCountSubscribers[c]; ok {
ch <- s.runningExecs[c]
}
s.lifecycleMu.Unlock()
}
}
func (s *service) getContainerPids(ctx context.Context, container *runc.Container) ([]uint32, error) {