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    Subject[PATCH AUTOSEL 4.19 180/258] percpu: convert spin_lock_irq to spin_lock_irqsave.
    Date
    From: Dennis Zhou <dennis@kernel.org>

    [ Upstream commit 6ab7d47bcbf0144a8cb81536c2cead4cde18acfe ]

    From Michael Cree:
    "Bisection lead to commit b38d08f3181c ("percpu: restructure
    locking") as being the cause of lockups at initial boot on
    the kernel built for generic Alpha.

    On a suggestion by Tejun Heo that:

    So, the only thing I can think of is that it's calling
    spin_unlock_irq() while irq handling isn't set up yet.
    Can you please try the followings?

    1. Convert all spin_[un]lock_irq() to
    spin_lock_irqsave/unlock_irqrestore()."

    Fixes: b38d08f3181c ("percpu: restructure locking")
    Reported-and-tested-by: Michael Cree <mcree@orcon.net.nz>
    Acked-by: Tejun Heo <tj@kernel.org>
    Signed-off-by: Dennis Zhou <dennis@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    mm/percpu-km.c | 5 +++--
    1 file changed, 3 insertions(+), 2 deletions(-)

    diff --git a/mm/percpu-km.c b/mm/percpu-km.c
    index 38de70ab1a0d..0f643dc2dc65 100644
    --- a/mm/percpu-km.c
    +++ b/mm/percpu-km.c
    @@ -50,6 +50,7 @@ static struct pcpu_chunk *pcpu_create_chunk(gfp_t gfp)
    const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
    struct pcpu_chunk *chunk;
    struct page *pages;
    + unsigned long flags;
    int i;

    chunk = pcpu_alloc_chunk(gfp);
    @@ -68,9 +69,9 @@ static struct pcpu_chunk *pcpu_create_chunk(gfp_t gfp)
    chunk->data = pages;
    chunk->base_addr = page_address(pages) - pcpu_group_offsets[0];

    - spin_lock_irq(&pcpu_lock);
    + spin_lock_irqsave(&pcpu_lock, flags);
    pcpu_chunk_populated(chunk, 0, nr_pages, false);
    - spin_unlock_irq(&pcpu_lock);
    + spin_unlock_irqrestore(&pcpu_lock, flags);

    pcpu_stats_chunk_alloc();
    trace_percpu_create_chunk(chunk->base_addr);
    --
    2.19.1
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