fix(server): retry wl_event_loop_dispatch interrupted by signals

commit: ad674f5256764b698efd3fe6a0389ac5cc6f81ef
author: brice · 25d ago · 2026-09-27 18:15 UTC
committer: brice · 25d ago · 2026-09-27 18:47 UTC
parent: 6f1d5dd
signature: GPG VerifiedCD88F9E564E0102646FB6077A1A07C7C7C3E349D · arch-gpg Verified for the committer email
refs: tag: v0.5.0

2 files · +29 -1

M server/display.go +9 -1


@@ -154,6 +154,7 @@ func (d *Display) Run(ctx context.Context) error {
154	154		defer runtime.UnlockOSThread()
155	155		defer close(d.stopped)
156	156		defer d.destroy()
	157	+	consecutiveFailures := 0
157	158		for {
158	159		if ctx.Err() != nil {
159	160		return nil

@@ -171,8 +172,15 @@ func (d *Display) Run(ctx context.Context) error {
171	172		wlDisplayFlushClients(d.c)
172	173		// The timeout only bounds how late ctx cancellation is seen.
173	174		if wlEventLoopDispatch(d.loop, 100) < 0 {
174		-	return errors.New("purego-libwayland: wl_event_loop_dispatch failed")
	175	+	errno := lastErrno()
	176	+	consecutiveFailures++
	177	+	// epoll_wait is interrupted by Go's preemption signals (EINTR); a persistent failure (EBADF, EINVAL) repeats.
	178	+	if consecutiveFailures < 16 {
	179	+	continue
	180	+	}
	181	+	return fmt.Errorf("purego-libwayland: wl_event_loop_dispatch failed %d times in a row: %w", consecutiveFailures, errno)
175	182		}
	183	+	consecutiveFailures = 0
176	184		wlDisplayFlushClients(d.c)
177	185		}
178	186		}

 	defer runtime.UnlockOSThread()
 	defer close(d.stopped)
 	defer d.destroy()
+	consecutiveFailures := 0
 	for {
 		if ctx.Err() != nil {
 			return nil
 		wlDisplayFlushClients(d.c)
 		// The timeout only bounds how late ctx cancellation is seen.
 		if wlEventLoopDispatch(d.loop, 100) < 0 {
-			return errors.New("purego-libwayland: wl_event_loop_dispatch failed")
+			errno := lastErrno()
+			consecutiveFailures++
+			// epoll_wait is interrupted by Go's preemption signals (EINTR); a persistent failure (EBADF, EINVAL) repeats.
+			if consecutiveFailures < 16 {
+				continue
+			}
+			return fmt.Errorf("purego-libwayland: wl_event_loop_dispatch failed %d times in a row: %w", consecutiveFailures, errno)
 		}
+		consecutiveFailures = 0
 		wlDisplayFlushClients(d.c)
 	}
 }

M server/lib.go +20 -0


@@ -6,6 +6,7 @@ import (
6	6		"unsafe"
7	7
8	8		"github.com/bnema/purego"
	9	+	"golang.org/x/sys/unix"
9	10		)
10	11
11	12		// libwayland-server entry points. Only non-varargs functions are bound.

@@ -30,6 +31,7 @@ var (
30	31
31	32		symDisplayFlushClients, symEventLoopDispatch, symResourceCreate uintptr
32	33		symResourceSetDispatcher, symResourcePostEventArr, symResourceDestroy, symResourceGetID uintptr
	34	+	symErrnoLocation uintptr
33	35
34	36		// Shared C callbacks. purego callbacks are never freed, so there is one
35	37		// of each for the whole process.

@@ -82,6 +84,19 @@ func load() error {
82	84		return
83	85		}
84	86		}
	87	+	symErrnoLocation, err = purego.Dlsym(lib, "__errno_location")
	88	+	if err != nil {
	89	+	libc, openErr := purego.Dlopen("libc.so.6", purego.RTLD_NOW\|purego.RTLD_GLOBAL)
	90	+	if openErr != nil {
	91	+	loadErr = fmt.Errorf("purego-libwayland: open libc.so.6: %w", openErr)
	92	+	return
	93	+	}
	94	+	symErrnoLocation, err = purego.Dlsym(libc, "__errno_location")
	95	+	if err != nil {
	96	+	loadErr = fmt.Errorf("purego-libwayland: resolve __errno_location: %w", err)
	97	+	return
	98	+	}
	99	+	}
85	100
86	101		cbDispatcher = purego.NewCallbackInts(func(a *purego.CallbackArgs) uintptr {
87	102		// C memory owned by libwayland; reinterpret pointer bits without uintptr-to-pointer conversion.

@@ -111,6 +126,11 @@ func wlEventLoopDispatch(loop uintptr, timeout int32) int32 {
111	126		r, _, _ := purego.Syscall6(symEventLoopDispatch, loop, uintptr(timeout), 0, 0, 0, 0)
112	127		return int32(r)
113	128		}
	129	+	func lastErrno() unix.Errno {
	130	+	p, _, _ := purego.Syscall6(symErrnoLocation, 0, 0, 0, 0, 0, 0)
	131	+	// C memory owned by libc; reinterpret pointer bits without uintptr-to-pointer conversion.
	132	+	return unix.Errno((int32)(unsafe.Pointer(&p)))
	133	+	}
114	134		func wlResourceCreate(client, iface uintptr, version int32, id uint32) uintptr {
115	135		r, _, _ := purego.Syscall6(symResourceCreate, client, iface, uintptr(version), uintptr(id), 0, 0)
116	136		return r


@@ -6,6 +6,7 @@ import (
6	"unsafe"	6		"unsafe"
7		7
8	"github.com/bnema/purego"	8		"github.com/bnema/purego"
		9	+	"golang.org/x/sys/unix"
9	)	10		)
10		11
11	// libwayland-server entry points. Only non-varargs functions are bound.	12		// libwayland-server entry points. Only non-varargs functions are bound.

@@ -30,6 +31,7 @@ var (
30		31
31	symDisplayFlushClients, symEventLoopDispatch, symResourceCreate uintptr	32		symDisplayFlushClients, symEventLoopDispatch, symResourceCreate uintptr
32	symResourceSetDispatcher, symResourcePostEventArr, symResourceDestroy, symResourceGetID uintptr	33		symResourceSetDispatcher, symResourcePostEventArr, symResourceDestroy, symResourceGetID uintptr
		34	+	symErrnoLocation uintptr
33		35
34	// Shared C callbacks. purego callbacks are never freed, so there is one	36		// Shared C callbacks. purego callbacks are never freed, so there is one
35	// of each for the whole process.	37		// of each for the whole process.

@@ -82,6 +84,19 @@ func load() error {
82	return	84		return
83	}	85		}
84	}	86		}
		87	+	symErrnoLocation, err = purego.Dlsym(lib, "__errno_location")
		88	+	if err != nil {
		89	+	libc, openErr := purego.Dlopen("libc.so.6", purego.RTLD_NOW\|purego.RTLD_GLOBAL)
		90	+	if openErr != nil {
		91	+	loadErr = fmt.Errorf("purego-libwayland: open libc.so.6: %w", openErr)
		92	+	return
		93	+	}
		94	+	symErrnoLocation, err = purego.Dlsym(libc, "__errno_location")
		95	+	if err != nil {
		96	+	loadErr = fmt.Errorf("purego-libwayland: resolve __errno_location: %w", err)
		97	+	return
		98	+	}
		99	+	}
85		100
86	cbDispatcher = purego.NewCallbackInts(func(a *purego.CallbackArgs) uintptr {	101		cbDispatcher = purego.NewCallbackInts(func(a *purego.CallbackArgs) uintptr {
87	// C memory owned by libwayland; reinterpret pointer bits without uintptr-to-pointer conversion.	102		// C memory owned by libwayland; reinterpret pointer bits without uintptr-to-pointer conversion.

@@ -111,6 +126,11 @@ func wlEventLoopDispatch(loop uintptr, timeout int32) int32 {
111	r, _, _ := purego.Syscall6(symEventLoopDispatch, loop, uintptr(timeout), 0, 0, 0, 0)	126		r, _, _ := purego.Syscall6(symEventLoopDispatch, loop, uintptr(timeout), 0, 0, 0, 0)
112	return int32(r)	127		return int32(r)
113	}	128		}
		129	+	func lastErrno() unix.Errno {
		130	+	p, _, _ := purego.Syscall6(symErrnoLocation, 0, 0, 0, 0, 0, 0)
		131	+	// C memory owned by libc; reinterpret pointer bits without uintptr-to-pointer conversion.
		132	+	return unix.Errno((int32)(unsafe.Pointer(&p)))
		133	+	}
114	func wlResourceCreate(client, iface uintptr, version int32, id uint32) uintptr {	134		func wlResourceCreate(client, iface uintptr, version int32, id uint32) uintptr {
115	r, _, _ := purego.Syscall6(symResourceCreate, client, iface, uintptr(version), uintptr(id), 0, 0)	135		r, _, _ := purego.Syscall6(symResourceCreate, client, iface, uintptr(version), uintptr(id), 0, 0)
116	return r	136		return r