Skip to content
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.

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

Poll directory changes before resolving start promise on Windows #9

Merged
merged 1 commit into from Jun 14, 2019

Conversation

@as-cii
Copy link

@as-cii as-cii commented Jun 14, 2019

Refs: atom/atom#19507
Refs: atom/atom#19442 (comment)

When watching a path on Windows, a new thread gets spawned and a function is scheduled to be executed onto such thread. This function's responsibility is to invoke ReadDirectoryChangesW for the first time and to wake up the thread which invoked Watcher::start, signaling that nsfw is ready to report events.

Previously, the main thread would be woken up before calling ReadDirectoryChangesW. If any event occurred before or as ReadDirectoryChangesW took place, it wouldn't be reported to clients because that API only reports changes that occur between calls to it. This is an excerpt from MSDN:

When you first call ReadDirectoryChangesW, the system allocates a buffer to store change information. This buffer is associated with the directory handle until it is closed and its size does not change during its lifetime. Directory changes that occur between calls to this function are added to the buffer and then returned with the next call.

This pull request fixes the issue by waiting for ReadDirectoryChangesW to have been called before waking up the main thread. This ensures that file system events occurring after watching has started are always reported to clients.

/cc: @jasonrudolph @rafeca @nathansobo

When watching a path on Windows, a new thread gets spawned and a
function is scheduled to be executed onto such thread. This function's
responsibility is to invoke `ReadDirectoryChangesW` for the first time
and to wake up the thread which invoked `Watcher::start`, signaling that
nsfw is ready to report events.

Previously, the main thread would be woken up _before_ calling
`ReadDirectoryChangesW`. If any event occurred before or as
`ReadDirectoryChangesW` took place, it wouldn't be reported to clients
because that API only reports changes that occur _between_ calls to it.

This commit fixes the issue by waiting for `ReadDirectoryChangesW` to
have been called before waking up the main thread. This ensures that
file system events occurring after watching has started are always 
reported to clients.
@jasonrudolph
Copy link
Member

@jasonrudolph jasonrudolph commented Jun 14, 2019

@as-cii: I think this change looks good, but I'd feel more comfortable if we could verify that nsfw's CI passes following these changes. How would you feel about opening another upstream pull request for this change in https://github.com/Axosoft/nsfw so that we can see CI run and verify that all the CI runs pass?

@as-cii as-cii merged commit 8a87541 into master Jun 14, 2019
@as-cii as-cii deleted the fix-race-on-start branch Jun 14, 2019
jasonrudolph added a commit to atom/atom that referenced this pull request Jun 14, 2019
…fix"

This reverts commit a0742f8.

As of 8734f66, we're now using the nsfw fixes from
atom/nsfw#9, which should resolve the flakiness
we were seeing on Windows.
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Projects
None yet
Linked issues

Successfully merging this pull request may close these issues.

None yet

2 participants
You can’t perform that action at this time.