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| author | Tejun Heo <tj@kernel.org> | 2010-09-21 07:57:19 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-09-26 17:21:27 -0700 |
| commit | 61e0ce1b361c699387029fdda4ba08e6ae4af326 (patch) | |
| tree | a82bae6ff62f619fede340117343d620db8e96e2 | |
| parent | e286d83959320fcf7eadfc81aeceb6e1a81667c9 (diff) | |
| download | lwn-61e0ce1b361c699387029fdda4ba08e6ae4af326.tar.gz lwn-61e0ce1b361c699387029fdda4ba08e6ae4af326.zip | |
percpu: fix pcpu_last_unit_cpu
commit 46b30ea9bc3698bc1d1e6fd726c9601d46fa0a91 upstream.
pcpu_first/last_unit_cpu are used to track which cpu has the first and
last units assigned. This in turn is used to determine the span of a
chunk for man/unmap cache flushes and whether an address belongs to
the first chunk or not in per_cpu_ptr_to_phys().
When the number of possible CPUs isn't power of two, a chunk may
contain unassigned units towards the end of a chunk. The logic to
determine pcpu_last_unit_cpu was incorrect when there was an unused
unit at the end of a chunk. It failed to ignore the unused unit and
assigned the unused marker NR_CPUS to pcpu_last_unit_cpu.
This was discovered through kdump failure which was caused by
malfunctioning per_cpu_ptr_to_phys() on a kvm setup with 50 possible
CPUs by CAI Qian.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: CAI Qian <caiqian@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | mm/percpu.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/percpu.c b/mm/percpu.c index 5adfc268b408..3bfd6e251f19 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -1702,9 +1702,9 @@ int __init pcpu_setup_first_chunk(const struct pcpu_alloc_info *ai, if (pcpu_first_unit_cpu == NR_CPUS) pcpu_first_unit_cpu = cpu; + pcpu_last_unit_cpu = cpu; } } - pcpu_last_unit_cpu = cpu; pcpu_nr_units = unit; for_each_possible_cpu(cpu) |