Fix lock-order inversion deadlock in Diags::tag_activated#13106
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This fixes a deadlock between Diags::tag_table_lock and the dynamic loader lock. The issue occurs when Regex::exec() lazily constructs a thread_local RegexContext whose destructor registration via __cxa_thread_atexit_impl acquires the dl loader lock. Holding tag_table_lock across exec() creates a lock-order inversion with dlopen() callers that construct a DbgCtl during plugin static initialization (which takes tag_table_lock while already holding the dl loader lock). This changes activated_tags to use std::shared_ptr<Regex> and snapshots the regex under the lock before releasing it and calling exec(). The same pattern is applied to activate_taglist() which now compiles the new regex outside the lock. Fixes: apache#13101
cmcfarlen
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Apr 23, 2026
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Cherry-picked to 10.2.x |
cmcfarlen
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Apr 29, 2026
(cherry picked from commit 571ee72)
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This fixes a deadlock between Diags::tag_table_lock and the dynamic loader lock. The issue occurs when Regex::exec() lazily constructs a thread_local RegexContext whose destructor registration via __cxa_thread_atexit_impl acquires the dl loader lock. Holding tag_table_lock across exec() creates a lock-order inversion with dlopen() callers that construct a DbgCtl during plugin static initialization (which takes tag_table_lock while already holding the dl loader lock).
This changes activated_tags to use std::shared_ptr and snapshots the regex under the lock before releasing it and calling exec(). The same pattern is applied to activate_taglist() which now compiles the new regex outside the lock.
Fixes: #13101