Fix pending HostDB DNS queue removal race#13294
Open
bneradt wants to merge 1 commit into
Open
Conversation
A crash was observed while HostDB was probing pending DNS state for a
request, with the stack unwinding through the DNS lookup path:
#4 swoc::bwf::ExternalNames::operator()(...)
at libswoc_1.5.15/include/swoc/bwf_base.h:610
#7 HostDBContinuation::do_dns(...)
at src/iocore/hostdb/HostDB.cc:1352
apache#11 probe(...)
at src/iocore/hostdb/HostDB.cc:581
The core showed an obviously corrupted ExternalNames this pointer while
HostDB was allocating a continuation from the pending DNS path. The local
signal cleanup path could edit the pending-DNS queue without the bucket
lock, leaving stale revalidation readers able to walk links while they
were being changed.
This routes that cleanup through the locked pending-DNS removal helper
and uses its result to decide whether the continuation still owns
self-cleanup. This keeps queue membership checks and removals
synchronized without changing the timeout path's lifetime behavior.
bneradt
force-pushed
the
fix-hostdb-pending-dns-race
branch
from
bd24b72 to
8de3716
Compare
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
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
A crash was observed while HostDB was probing pending DNS state for a
request, with the stack unwinding through the DNS lookup path:
The core showed an obviously corrupted ExternalNames this pointer while
HostDB was allocating a continuation from the pending DNS path. The local
signal cleanup path could edit the pending-DNS queue without the bucket
lock, leaving stale revalidation readers able to walk links while they
were being changed.
This routes that cleanup through the locked pending-DNS removal helper
and uses its result to decide whether the continuation still owns
self-cleanup. This keeps queue membership checks and removals
synchronized without changing the timeout path's lifetime behavior.