Remove GVL unlocking at all functions which process data modifiable in a second thread#723
Open
larskanis wants to merge 1 commit into
Open
Remove GVL unlocking at all functions which process data modifiable in a second thread#723larskanis wants to merge 1 commit into
larskanis wants to merge 1 commit into
Conversation
larskanis
changed the title
larskanis
force-pushed
the
DFVULN-801-2
branch
6 times, most recently
from
2facd7a to
b9a2e30
Compare
…n a second thread This removes possible VM crashs when data to be sent is modified/cleared in a second thread. It works by keeping the GVL lock for libpq functions that don't immediately process all the data and don't make a copy of it. These are the `PQsend*`, `PQexec*` and some related functions. Since pg-1.3 all the blocking functions or states are avoided by using the non-blocking API of libpq. Therefore holding the GVL somewhat longer shouldn't matter that much. Having some libpq function with and without unlocked GVL, results in `rb_thread_call_with_gvl()` sometimes needed and sometimes not to process callbacks. Therefore `ruby_thread_has_gvl_p()` is used to check if it's needed on ruby<4.0. In ruby-4.0+ `rb_thread_call_with_gvl()` doesn't care about whether GVL is already locked or not, so that it can be called in both cases. Fixes #721
cbandy
approved these changes
Jun 15, 2026
cbandy
left a comment
cbandy
left a comment
Contributor
There was a problem hiding this comment.
📝 PR title says GLV instead of GVL
|
|
||
|
|
||
| /* | ||
| * Definitions of blocking functions and their parameters |
Contributor
There was a problem hiding this comment.
It might be good to explain how one decides which functions to include/exclude from this list.
cbandy
reviewed
Jun 15, 2026
Comment on lines
-259
to
-266
| function(PQsendQuery, GVL_TYPE_NONVOID, int, const char *, query) \ | ||
| function(PQsendQueryParams, GVL_TYPE_NONVOID, int, int, resultFormat) \ | ||
| function(PQsendPrepare, GVL_TYPE_NONVOID, int, const Oid *, paramTypes) \ | ||
| function(PQsendQueryPrepared, GVL_TYPE_NONVOID, int, int, resultFormat) \ | ||
| function(PQsendDescribePrepared, GVL_TYPE_NONVOID, int, const char *, stmt) \ | ||
| function(PQsendDescribePortal, GVL_TYPE_NONVOID, int, const char *, portal) \ | ||
| function(PQsendClosePrepared, GVL_TYPE_NONVOID, int, const char *, stmt) \ | ||
| function(PQsendClosePortal, GVL_TYPE_NONVOID, int, const char *, portal) \ |
Contributor
There was a problem hiding this comment.
These are async, and docs describe them as returns 1 if it was able to dispatch the request, and 0 if not. Is it just a socket write? What can block during these?
larskanis
changed the title
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
This removes possible VM crashs when data to be sent is modified/cleared in a second thread.
It works by keeping the GVL lock for libpq functions that don't immediately process all the data and don't make a copy of it.
These are the
PQsend*,PQexec*and some related functions.Since pg-1.3 all the blocking functions or states are avoided by using the non-blocking API of libpq.
Therefore holding the GVL somewhat longer shouldn't matter that much.
Having some libpq function with and without unlocked GVL, results in
rb_thread_call_with_gvl()sometimes needed and sometimes not to process callbacks.Therefore
ruby_thread_has_gvl_p()is used to check if it's needed on ruby<4.0.In ruby-4.0+
rb_thread_call_with_gvl()doesn't care about whether GVL is already locked or not, so that it can be called in both cases.Fixes #721