fix: store and execute desired action on emergency action

Fixes #7854

Talos runs an emergency handler if the sequence experience and
unrecoverable failure. The emergency handler was unconditionally
executing "reboot" action if no other action was received (which only
gets received if the sequence completes successfully), so the Shutdown
request might result in a Reboot behavior on error during shutdown
phase.

This is not a pretty fix, but it's hard to deliver the intent from one
part of the code to another right now, so instead use a global variable
which stores default emergency intention, and gets overridden early in
the Shutdown sequence.

Signed-off-by: Andrey Smirnov <andrey.smirnov@siderolabs.com>

internal/app/machined/main.go

@@ -27,6 +27,7 @@ import (
 	"github.com/siderolabs/talos/internal/app/apid"
 	"github.com/siderolabs/talos/internal/app/dashboard"
 	"github.com/siderolabs/talos/internal/app/machined/pkg/runtime"
+	"github.com/siderolabs/talos/internal/app/machined/pkg/runtime/emergency"
 	v1alpha1runtime "github.com/siderolabs/talos/internal/app/machined/pkg/runtime/v1alpha1"
 	"github.com/siderolabs/talos/internal/app/machined/pkg/system"
 	"github.com/siderolabs/talos/internal/app/machined/pkg/system/services"
@@ -95,7 +96,7 @@ func syncNonVolatileStorageBuffers() {
 
 //nolint:gocyclo
 func handle(ctx context.Context, err error) {
-	rebootCmd := unix.LINUX_REBOOT_CMD_RESTART
+	rebootCmd := int(emergency.RebootCmd.Load())
 
 	var rebootErr runtime.RebootError
 

internal/app/machined/pkg/controllers/network/platform_config.go

@@ -534,6 +534,13 @@ func (ctrl *PlatformConfigController) runWithRestarts(ctx context.Context, logge
 			return
 		}
 
+		// skip restarting if context is already done
+		select {
+		case <-ctx.Done():
+			return
+		default:
+		}
+
 		interval := backoff.NextBackOff()
 
 		logger.Error("restarting platform network config", zap.Duration("interval", interval), zap.Error(err))

internal/app/machined/pkg/runtime/emergency/emergency.go

@@ -0,0 +1,19 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+// Package emergency provides values to handle emergency (panic/unrecoverable error) handling for machined.
+package emergency
+
+import (
+	"sync/atomic"
+
+	"golang.org/x/sys/unix"
+)
+
+// RebootCmd is a command to reboot the system after an unrecoverable error.
+var RebootCmd atomic.Int64
+
+func init() {
+	RebootCmd.Store(unix.LINUX_REBOOT_CMD_RESTART)
+}

internal/app/machined/pkg/runtime/v1alpha1/v1alpha1_sequencer.go

@@ -375,7 +375,10 @@ func (*Sequencer) Reset(r runtime.Runtime, in runtime.ResetOptions) []runtime.Ph
 
 // Shutdown is the shutdown sequence.
 func (*Sequencer) Shutdown(r runtime.Runtime, in *machineapi.ShutdownRequest) []runtime.Phase {
-	phases := PhaseList{}.AppendWhen(
+	phases := PhaseList{}.Append(
+		"storeShudown",
+		StoreShutdownEmergency,
+	).AppendWhen(
 		!in.GetForce() && !r.Config().Machine().Kubelet().SkipNodeRegistration(),
 		"drain",
 		CordonAndDrainNode,

internal/app/machined/pkg/runtime/v1alpha1/v1alpha1_sequencer_tasks.go

@@ -47,6 +47,7 @@ import (
 	installer "github.com/siderolabs/talos/cmd/installer/pkg/install"
 	"github.com/siderolabs/talos/internal/app/machined/pkg/runtime"
 	"github.com/siderolabs/talos/internal/app/machined/pkg/runtime/disk"
+	"github.com/siderolabs/talos/internal/app/machined/pkg/runtime/emergency"
 	"github.com/siderolabs/talos/internal/app/machined/pkg/runtime/v1alpha1/bootloader/grub"
 	"github.com/siderolabs/talos/internal/app/machined/pkg/runtime/v1alpha1/platform"
 	"github.com/siderolabs/talos/internal/app/machined/pkg/system"
@@ -2255,6 +2256,17 @@ func FlushMeta(runtime.Sequence, any) (runtime.TaskExecutionFunc, string) {
 	}, "flushMeta"
 }
 
+// StoreShutdownEmergency stores shutdown emergency state.
+func StoreShutdownEmergency(runtime.Sequence, any) (runtime.TaskExecutionFunc, string) {
+	return func(ctx context.Context, logger *log.Logger, r runtime.Runtime) error {
+		// for shutdown sequence, store power_off as the intent, it will be picked up
+		// by emergency handled in machined/main.go if the Shutdown sequence fails
+		emergency.RebootCmd.Store(unix.LINUX_REBOOT_CMD_POWER_OFF)
+
+		return nil
+	}, "storeShutdownEmergency"
+}
+
 func pauseOnFailure(callback func(runtime.Sequence, any) (runtime.TaskExecutionFunc, string),
 	timeout time.Duration,
 ) func(seq runtime.Sequence, data any) (runtime.TaskExecutionFunc, string) {