Enum LockError 

#[non_exhaustive]
pub enum LockError {
    Map {
        bytes: usize,
        source: Error,
    },
    Guard {
        source: Error,
    },
    Refused {
        bytes: usize,
        limit: Option<u64>,
        source: Error,
    },
    Dump {
        source: Error,
    },
    Unavailable,
    Forked,
    Untracked {
        source: Error,
    },
    Alignment {
        align: usize,
        page: usize,
    },
}

Why a Locked value could not be created, or why its memory is not locked.

Refused, Dump, Untracked, Unavailable and Forked describe a degraded value that exists: under LockPolicy::BestEffort the first four are reported by Locked::lock_error from construction on, and Forked from the moment a forked child looks. Locked::require_locked turns any of them into an error and drops the value. The other variants mean no value was created.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Map

The operating system would not map the region at all.

Fields

bytes: usize

The size of the mapping requested, guard pages included.

source: Error

The OS error.

Guard

The region was mapped but a guard page could not be protected.

Fields

source: Error

The OS error.

Refused

mlock refused the interior, almost always because it would exceed RLIMIT_MEMLOCK (64 KiB by default on many Linux hosts). Every value costs at least one page of that limit whatever its size, so the default holds sixteen 4 KiB-page values, or a single one where pages are 64 KiB. Raise the limit with ulimit -l, LimitMEMLOCK= in a systemd unit, or the container runtime’s ulimit setting.

Fields

bytes: usize

The bytes that would have been locked.

limit: Option<u64>

The soft RLIMIT_MEMLOCK at the time, when it is finite and readable.

source: Error

The OS error.

Dump

The region is locked but could not be excluded from core dumps (madvise(MADV_DONTDUMP) on Linux or Android was refused, which a seccomp filter can do). The bytes would appear in a core dump.

Fields

source: Error

The OS error.

Unavailable

This platform or build has no memory locking: non-Unix targets, Miri (which maps the region but cannot lock it) and Kani. The value is wiped on drop as usual.

Forked

The value was created in another process. Memory locks are not inherited across fork, so in the child the region is unlocked until Locked::relock is called there.

Untracked

This process cannot tell its values when they cross a fork: the atfork handler that counts forks could not be registered (only want of memory makes pthread_atfork fail). A forked child would then inherit a lock it does not have with nothing to say so, so the value is treated as unlocked here.

Fields

source: Error

The OS error.

Alignment

T needs an alignment larger than a page, which the region cannot provide.

Fields

align: usize

T’s alignment.

page: usize

The page size, or 0 when the backend has no pages.

Trait Implementations

impl Debug for LockError

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for LockError

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Error for LockError

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.