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    Subject[PATCH 10/27] Blackfin: fix deadlock in SMP IPI handler
    Date
    From: Sonic Zhang <sonic.zhang@analog.com>

    When a low priority interrupt (like ethernet) is triggered between 2 high
    priority IPI messages, a deadlock in disable_irq() is hit by the second
    IPI handler. This is because the second IPI message is queued within the
    first IPI handler, but the handler doesn't process all messages, and new
    ones are inserted rather than appended. So now we process all the pending
    messages, and append new ones to the pending list.

    URL: http://blackfin.uclinux.org/gf/tracker/5226
    Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
    Signed-off-by: Mike Frysinger <vapier@gentoo.org>
    ---
    arch/blackfin/mach-common/smp.c | 13 +++++++------
    1 files changed, 7 insertions(+), 6 deletions(-)

    diff --git a/arch/blackfin/mach-common/smp.c b/arch/blackfin/mach-common/smp.c
    index c187da2..6184005 100644
    --- a/arch/blackfin/mach-common/smp.c
    +++ b/arch/blackfin/mach-common/smp.c
    @@ -144,7 +144,7 @@ static void ipi_call_function(unsigned int cpu, struct ipi_message *msg)

    static irqreturn_t ipi_handler(int irq, void *dev_instance)
    {
    - struct ipi_message *msg, *mg;
    + struct ipi_message *msg;
    struct ipi_message_queue *msg_queue;
    unsigned int cpu = smp_processor_id();

    @@ -154,7 +154,8 @@ static irqreturn_t ipi_handler(int irq, void *dev_instance)
    msg_queue->count++;

    spin_lock(&msg_queue->lock);
    - list_for_each_entry_safe(msg, mg, &msg_queue->head, list) {
    + while (!list_empty(&msg_queue->head)) {
    + msg = list_entry(msg_queue->head.next, typeof(*msg), list);
    list_del(&msg->list);
    switch (msg->type) {
    case BFIN_IPI_RESCHEDULE:
    @@ -221,7 +222,7 @@ int smp_call_function(void (*func)(void *info), void *info, int wait)
    for_each_cpu_mask(cpu, callmap) {
    msg_queue = &per_cpu(ipi_msg_queue, cpu);
    spin_lock_irqsave(&msg_queue->lock, flags);
    - list_add(&msg->list, &msg_queue->head);
    + list_add_tail(&msg->list, &msg_queue->head);
    spin_unlock_irqrestore(&msg_queue->lock, flags);
    platform_send_ipi_cpu(cpu);
    }
    @@ -261,7 +262,7 @@ int smp_call_function_single(int cpuid, void (*func) (void *info), void *info,

    msg_queue = &per_cpu(ipi_msg_queue, cpu);
    spin_lock_irqsave(&msg_queue->lock, flags);
    - list_add(&msg->list, &msg_queue->head);
    + list_add_tail(&msg->list, &msg_queue->head);
    spin_unlock_irqrestore(&msg_queue->lock, flags);
    platform_send_ipi_cpu(cpu);

    @@ -292,7 +293,7 @@ void smp_send_reschedule(int cpu)

    msg_queue = &per_cpu(ipi_msg_queue, cpu);
    spin_lock_irqsave(&msg_queue->lock, flags);
    - list_add(&msg->list, &msg_queue->head);
    + list_add_tail(&msg->list, &msg_queue->head);
    spin_unlock_irqrestore(&msg_queue->lock, flags);
    platform_send_ipi_cpu(cpu);

    @@ -320,7 +321,7 @@ void smp_send_stop(void)
    for_each_cpu_mask(cpu, callmap) {
    msg_queue = &per_cpu(ipi_msg_queue, cpu);
    spin_lock_irqsave(&msg_queue->lock, flags);
    - list_add(&msg->list, &msg_queue->head);
    + list_add_tail(&msg->list, &msg_queue->head);
    spin_unlock_irqrestore(&msg_queue->lock, flags);
    platform_send_ipi_cpu(cpu);
    }
    --
    1.6.3.1


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