From 6a7fe61d74f80456b32cb46ef21715bbffaf49a7 Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Thu, 8 Jan 2026 15:07:03 -0800
Subject: [PATCH] std.Io.Threaded.operate: handle poll buffer exceeded

---
 lib/std/Io/Threaded.zig | 141 ++++++++++++++++++++--------------------
 1 file changed, 72 insertions(+), 69 deletions(-)

diff --git a/lib/std/Io/Threaded.zig b/lib/std/Io/Threaded.zig
index 1f4bcf3478..e58d923793 100644
--- a/lib/std/Io/Threaded.zig
+++ b/lib/std/Io/Threaded.zig
@@ -2458,81 +2458,84 @@ fn operate(userdata: ?*anyopaque, operations: []Io.Operation) void {
 
     var poll_buffer: [poll_buffer_len]posix.pollfd = undefined;
     var map_buffer: [poll_buffer_len]u8 = undefined; // poll_buffer index to operations index
-    var poll_i: usize = 0;
+    var operation_index: usize = 0;
 
-    // Put all the file reads with nonblocking enabled into the poll set.
-    if (operations.len > poll_buffer.len) @panic("TODO");
-
-    for (operations, 0..) |*operation, operation_index| switch (operation.*) {
-        .noop => continue,
-        .file_read_streaming => |*o| {
-            if (o.nonblocking) {
-                o.result = error.WouldBlock;
-                poll_buffer[poll_i] = .{
-                    .fd = o.file.handle,
-                    .events = posix.POLL.IN,
-                    .revents = undefined,
-                };
-                map_buffer[poll_i] = @intCast(operation_index);
-                poll_i += 1;
-            } else {
-                o.result = fileReadStreaming(o.file, o.data) catch |err| switch (err) {
-                    error.Canceled => {
-                        setOperationsCanceled(operations[operation_index..]);
-                        return;
-                    },
-                    else => err,
-                };
+    while (operation_index < operations.len) {
+        var poll_i: usize = 0;
+        while (operation_index < operations.len) : (operation_index += 1) {
+            switch (operations[operation_index]) {
+                .noop => continue,
+                .file_read_streaming => |*o| {
+                    if (o.nonblocking) {
+                        o.result = error.WouldBlock;
+                        poll_buffer[poll_i] = .{
+                            .fd = o.file.handle,
+                            .events = posix.POLL.IN,
+                            .revents = 0,
+                        };
+                        if (map_buffer.len - poll_i == 0) break;
+                        map_buffer[poll_i] = @intCast(operation_index);
+                        poll_i += 1;
+                    } else {
+                        o.result = fileReadStreaming(o.file, o.data) catch |err| switch (err) {
+                            error.Canceled => {
+                                setOperationsError(operations[operation_index..], error.Canceled);
+                                return;
+                            },
+                            else => err,
+                        };
+                    }
+                },
             }
-        },
-    };
-
-    if (poll_i == 0) {
-        @branchHint(.likely);
-        return;
-    }
-
-    while (true) {
-        const syscall = Syscall.start() catch |err| switch (err) {
-            error.Canceled => {
-                setAllOperationsError(operations, map_buffer[0..poll_i], error.Canceled);
-                return;
-            },
-        };
-        const poll_rc = posix.system.poll(&poll_buffer, poll_i, -1);
-        syscall.finish();
-        switch (posix.errno(poll_rc)) {
-            .SUCCESS => {
-                if (poll_rc == 0) {
-                    // Spurious timeout; handle same as INTR.
-                    continue;
-                }
-                break;
-            },
-            .INTR => continue,
-            .NOMEM => {
-                setAllOperationsError(operations, map_buffer[0..poll_i], error.SystemResources);
-                return;
-            },
-            else => {
-                setAllOperationsError(operations, map_buffer[0..poll_i], error.Unexpected);
-                return;
-            },
         }
-    }
 
-    for (poll_buffer[0..poll_i], map_buffer[0..poll_i]) |*poll_fd, operation_index| {
-        if (poll_fd.revents == 0) continue;
-        switch (operations[operation_index]) {
-            .noop => unreachable,
-            .file_read_streaming => |*o| {
-                o.result = fileReadStreaming(o.file, o.data);
-            },
+        if (poll_i == 0) {
+            @branchHint(.likely);
+            return;
+        }
+
+        while (true) {
+            const syscall = Syscall.start() catch |err| switch (err) {
+                error.Canceled => {
+                    setPollOperationsError(operations, map_buffer[0..poll_i], error.Canceled);
+                    setOperationsError(operations[operation_index..], error.Canceled);
+                    return;
+                },
+            };
+            const poll_rc = posix.system.poll(&poll_buffer, poll_i, -1);
+            syscall.finish();
+            switch (posix.errno(poll_rc)) {
+                .SUCCESS => {
+                    if (poll_rc == 0) {
+                        // Spurious timeout; handle same as INTR.
+                        continue;
+                    }
+                    for (poll_buffer[0..poll_i], map_buffer[0..poll_i]) |*poll_fd, i| {
+                        if (poll_fd.revents == 0) continue;
+                        switch (operations[i]) {
+                            .noop => unreachable,
+                            .file_read_streaming => |*o| {
+                                o.result = fileReadStreaming(o.file, o.data);
+                            },
+                        }
+                    }
+                    break;
+                },
+                .INTR => continue,
+                .NOMEM => {
+                    setPollOperationsError(operations, map_buffer[0..poll_i], error.SystemResources);
+                    break;
+                },
+                else => {
+                    setPollOperationsError(operations, map_buffer[0..poll_i], error.Unexpected);
+                    break;
+                },
+            }
         }
     }
 }
 
-fn setAllOperationsError(
+fn setPollOperationsError(
     operations: []Io.Operation,
     map: []const u8,
     err: error{ Canceled, SystemResources, Unexpected },
@@ -2543,10 +2546,10 @@ fn setAllOperationsError(
     };
 }
 
-fn setOperationsCanceled(operations: []Io.Operation) void {
+fn setOperationsError(operations: []Io.Operation, err: error{ Canceled, SystemResources, Unexpected }) void {
     for (operations) |*op| switch (op.*) {
         .noop => unreachable,
-        inline else => |*o| o.result = error.Canceled,
+        inline else => |*o| o.result = err,
     };
 }