net: netconsole: Defer netpoll cleanup to avoid lock release during list traversal

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Current issue:
- The `target_list_lock` spinlock is held while iterating over
  target_list() entries.
- Mid-loop, the lock is released to call __netpoll_cleanup(), then
  reacquired.
- This practice compromises the protection provided by
  `target_list_lock`.

Reason for current design:
1. __netpoll_cleanup() may sleep, incompatible with holding a spinlock.
2. target_list_lock must be a spinlock because write_msg() cannot sleep.
   (See commit b5427c2717 ("[NET] netconsole: Support multiple logging
    targets"))

Defer the cleanup of the netpoll structure to outside the
target_list_lock() protected area. Create another list
(target_cleanup_list) to hold the entries that need to be cleaned up,
and clean them using a mutex (target_cleanup_list_lock).

Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

...

This commit is contained in:

Breno Leitao 2024-08-08 05:25:11 -07:00 • committed by Paolo Abeni

parent f2ab4c1a92

commit 97714695ef

1 changed files with 67 additions and 16 deletions

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drivers/net/netconsole.c

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