Skip to content

Make access to sysfs lock-free #852

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom
Open
wants to merge 1 commit into
base: master
Choose a base branch
from
Open

Make access to sysfs lock-free #852

wants to merge 1 commit into from

Conversation

ms-hujia
Copy link

This PR aims to remove the lock used in SysFsAccessInterface. The lock is not necessary and should be avoided based on below facts:

  1. Simultaneous read/write operations against the same sysfs instance are atomic by design.
  2. For simultaneous read/write operations to different sysfs instances belonging to the same device, it's the driver's responsibility to ensure the data consistency. If a lock is needed at user-level, this usually indicates defect at device driver.
  3. According to the spec of Level Zero, most get/set function has the note The implementation of this function should be lock-free..

@bellekal
Copy link
Contributor

According to the spec of Level Zero, most get/set function has the note The implementation of this function should be lock-free..
Yes, It is recommended to have the implementation lock-free and not a mandatory requirement. Please refer to Terminology.

Can you please let us know actual requirement/issue so that, We will try to support.

bellekal
bellekal reviewed Oct 10, 2025
View reviewed changes
level_zero/sysman/source/shared/linux/sysman_fs_access_interface.cpp

template <typename T>
ze_result_t FsAccessInterface::readValue(const std::string file, T &val) {
auto lock = this->obtainMutex();
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Intention of having lock here is not for handling race conditions for sysfs file reads, But to ensure correct operations with FdCacheInterface (Which ensures quicker reads by avoiding redundant file open and file close operations when multiple reads are requested). Adding lock here ensures fd is not closed before read is completed in multi thread environment.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Reviewers

1 more reviewer

@bellekal bellekal bellekal left review comments

Reviewers whose approvals may not affect merge requirements

Assignees

No one assigned

Labels

None yet

Projects

None yet

Milestone

No milestone

Development

Successfully merging this pull request may close these issues.

2 participants

@ms-hujia @bellekal