Module robust_list 

Robust list syscalls: set_robust_list, get_robust_list

Robust lists allow the kernel to clean up held futex-based mutexes when a thread dies, preventing deadlocks.

Linux ABI (robust_list_head in userspace): offset 0: struct robust_list list (next pointer, 8 bytes) offset 8: long futex_offset (offset from list entry to futex int) offset 16: struct robust_list *list_op_pending (pending operation)

Total: 24 bytes on x86_64.

Constants

FUTEX_OWNER_DIED 🔒

Futex value bit: the owner has died.

ROBUST_LIST_LIMIT 🔒

Maximum number of entries to walk in a robust list (Linux uses 4096).

TID_MASK 🔒

Mask for the TID portion of a futex value.

Functions

cleanup_robust_list

Walk the robust list for a dying task and mark owned futexes as “owner died”.

mark_futex_owner_died 🔒

Mark a futex as owner-died if the current thread still holds it.

read_u32_from_user 🔒

Read a u32 from userspace memory at the given address.

sys_get_robust_list

SYS_GET_ROBUST_LIST (611): Get the robust list head for a task.

sys_set_robust_list

SYS_SET_ROBUST_LIST (610): Register the robust list head for the current task.