eventpoll: document ep_clear_and_put() two-pass pattern

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ep_clear_and_put() walks the rbtree twice: once to drain each epi's
pwqlist, then again to ep_remove() each entry. The split is
load-bearing -- fusing the passes into one loop would let a poll
callback still queued on some epi_i fire after epi_{i+k} has already
been freed -- but the previous comments described each pass in
isolation and did not explain the ordering invariant or the
cooperation with removal path C (eventpoll_release_file).

Add a function-level docblock that labels this as path B from the
top-of-file "Removal paths" section, names the two passes and the
ordering invariant, explains the pwqlist drain as synchronization
with in-flight ep_poll_callback() via whead->lock, describes the
C-path hand-off when epi_fget() returns NULL, and states the
ep->refcount invariant that keeps ep_remove()'s WARN_ON_ONCE safe
across the loop.

Also tighten the per-pass comments to one line each and fix the
minor grammar bug in the poll_wait release comment ("these file" ->
"poll-on-ep").

No functional change.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
Link: https://patch.msgid.link/20260424-work-epoll-rework-v1-5-249ed00a20f3@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>

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Christian Brauner 2026-04-24 15:46:36 +02:00

parent a573cb40f9

commit 858c14b1f0

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fs/eventpoll.c

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