diff options
| author | Hugh Dickins <hughd@google.com> | 2023-09-02 08:29:30 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2023-09-02 08:39:21 -0700 |
| commit | ee40d543e97d23d3392d8fb1ec9972eb4e9c7611 (patch) | |
| tree | 34a9b35afcedd52fdaf81a499efad59cb2d640a7 /kernel/sched/fair.c | |
| parent | 76be05d4fd6c91a3885298f1dc3efeef32846399 (diff) | |
mm/pagewalk: fix bootstopping regression from extra pte_unmap()
Mikhail reports early-6.6-based Fedora Rawhide not booting: "rcu_preempt
detected expedited stalls", minutes wait, and then hung_task splat while
kworker trying to synchronize_rcu_expedited(). Nothing logged to disk.
He bisected to my 6.6 a349d72fd9ef ("mm/pgtable: add rcu_read_lock() and
rcu_read_unlock()s"): but the one to blame is my 6.5 commit to fix the
espfix "bad pmd" warnings when booting x86_64 with CONFIG_EFI_PGT_DUMP=y.
Gaah, that added an "addr >= TASK_SIZE" check to avoid pte_offset_map(),
but failed to add the equivalent check when choosing to pte_unmap().
It's not a problem on 6.5 (for different reasons, it's harmless on both
64-bit and 32-bit), but becomes a bootstopper on 6.6 with the unbalanced
rcu_read_unlock() - RCU has a WARN_ON_ONCE for that, but it would have
scrolled off Mikhail's console too quickly.
Reported-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Closes: https://lore.kernel.org/linux-mm/CABXGCsNi8Tiv5zUPNXr6UJw6qV1VdaBEfGqEAMkkXE3QPvZuAQ@mail.gmail.com/
Fixes: 8b1cb4a2e819 ("mm/pagewalk: fix EFI_PGT_DUMP of espfix area")
Fixes: a349d72fd9ef ("mm/pgtable: add rcu_read_lock() and rcu_read_unlock()s")
Signed-off-by: Hugh Dickins <hughd@google.com>
Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/sched/fair.c')
0 files changed, 0 insertions, 0 deletions