---
name: "io_uring_register_sync_cancel"
section: "3"
platform: "linux"
package: "liburing"
version: "2.15-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/io_uring_register_sync_cancel"
---

# io\_uring\_register\_sync\_cancel(3)

issue a synchronous cancelation request

## NAME

io\_uring\_register\_sync\_cancel - issue a synchronous cancelation request

## SYNOPSIS

```
#include <liburing.h>
```

**int io\_uring\_register\_sync\_cancel(struct io\_uring \****ring***,**                                   **struct io\_uring\_sync\_cancel\_reg \****reg***);**

## DESCRIPTION

The [**io\_uring\_register\_sync\_cancel**(3)](/io_uring_register_sync_cancel/3.md) function performs a synchronous cancelation request based on the parameters specified in *reg .*

The *reg* argument must be filled in with the appropriate information for the cancelation request. It looks as follows:

```
struct io_uring_sync_cancel_reg {
    __u64 addr;
    __s32 fd;
    __u32 flags;
    struct __kernel_timespec timeout;
    __u8 opcode;
    __u8 pad[7];
    __u64 pad2[3];
};
```

The arguments largely mirror what the async prep functions support, see [**io\_uring\_prep\_cancel**(3)](/io_uring_prep_cancel/3.md) for details. Similarly, the return value is the same. The exception is the *timeout* argument, which can be used to limit the time that the kernel will wait for cancelations to be successful. If the *tv\_sec* and *tv\_nsec* values are set to anything but **-1UL ,** then they indicate a relative timeout upon which cancelations should be completed by.

The *pad* values must be zero filled.

## RETURN VALUE

See [**io\_uring\_prep\_cancel**(3)](/io_uring_prep_cancel/3.md) for details on the return value. If *timeout* is set to indicate a timeout, then **-ETIME** will be returned if exceeded. If an unknown value is set in the request, or if the pad values are not cleared to zero, then *-EINVAL* is returned.

## SEE ALSO

[**io\_uring\_prep\_cancel**(3)](/io_uring_prep_cancel/3.md)