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    Subject[patch 35/71] x86: fix SMP alternatives: use mutex instead of spinlock, text_poke is sleepable
    2.6.26-stable review patch.  If anyone has any objections, please let us
    know.

    ------------------
    From: Pekka Paalanen <pq@iki.fi>

    commit 2f1dafe50cc4e58a239fd81bd47f87f32042a1ee upstream

    text_poke is sleepable.
    The original fix by Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>.

    Signed-off-by: Pekka Paalanen <pq@iki.fi>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    arch/x86/kernel/alternative.c | 18 +++++++++---------
    1 file changed, 9 insertions(+), 9 deletions(-)

    --- a/arch/x86/kernel/alternative.c
    +++ b/arch/x86/kernel/alternative.c
    @@ -1,6 +1,6 @@
    #include <linux/module.h>
    #include <linux/sched.h>
    -#include <linux/spinlock.h>
    +#include <linux/mutex.h>
    #include <linux/list.h>
    #include <linux/kprobes.h>
    #include <linux/mm.h>
    @@ -279,7 +279,7 @@ struct smp_alt_module {
    struct list_head next;
    };
    static LIST_HEAD(smp_alt_modules);
    -static DEFINE_SPINLOCK(smp_alt);
    +static DEFINE_MUTEX(smp_alt);
    static int smp_mode = 1; /* protected by smp_alt */

    void alternatives_smp_module_add(struct module *mod, char *name,
    @@ -312,12 +312,12 @@ void alternatives_smp_module_add(struct
    __func__, smp->locks, smp->locks_end,
    smp->text, smp->text_end, smp->name);

    - spin_lock(&smp_alt);
    + mutex_lock(&smp_alt);
    list_add_tail(&smp->next, &smp_alt_modules);
    if (boot_cpu_has(X86_FEATURE_UP))
    alternatives_smp_unlock(smp->locks, smp->locks_end,
    smp->text, smp->text_end);
    - spin_unlock(&smp_alt);
    + mutex_unlock(&smp_alt);
    }

    void alternatives_smp_module_del(struct module *mod)
    @@ -327,17 +327,17 @@ void alternatives_smp_module_del(struct
    if (smp_alt_once || noreplace_smp)
    return;

    - spin_lock(&smp_alt);
    + mutex_lock(&smp_alt);
    list_for_each_entry(item, &smp_alt_modules, next) {
    if (mod != item->mod)
    continue;
    list_del(&item->next);
    - spin_unlock(&smp_alt);
    + mutex_unlock(&smp_alt);
    DPRINTK("%s: %s\n", __func__, item->name);
    kfree(item);
    return;
    }
    - spin_unlock(&smp_alt);
    + mutex_unlock(&smp_alt);
    }

    void alternatives_smp_switch(int smp)
    @@ -359,7 +359,7 @@ void alternatives_smp_switch(int smp)
    return;
    BUG_ON(!smp && (num_online_cpus() > 1));

    - spin_lock(&smp_alt);
    + mutex_lock(&smp_alt);

    /*
    * Avoid unnecessary switches because it forces JIT based VMs to
    @@ -383,7 +383,7 @@ void alternatives_smp_switch(int smp)
    mod->text, mod->text_end);
    }
    smp_mode = smp;
    - spin_unlock(&smp_alt);
    + mutex_unlock(&smp_alt);
    }

    #endif
    --


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