net/mlx4_en: Fix mixed PFC and Global pause user control requests

[pandora-kernel.git] / kernel / sched_clock.c

diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c
index 9d8af0b..c3ae144 100644 (file)
--- a/kernel/sched_clock.c
+++ b/kernel/sched_clock.c
@@ -62,7 +62,7 @@
  */
 #include <linux/spinlock.h>
 #include <linux/hardirq.h>
-#include <linux/module.h>
+#include <linux/export.h>
 #include <linux/percpu.h>
 #include <linux/ktime.h>
 #include <linux/sched.h>
@@ -176,10 +176,36 @@ static u64 sched_clock_remote(struct sched_clock_data *scd)
        u64 this_clock, remote_clock;
        u64 *ptr, old_val, val;
 
+#if BITS_PER_LONG != 64
+again:
+       /*
+        * Careful here: The local and the remote clock values need to
+        * be read out atomic as we need to compare the values and
+        * then update either the local or the remote side. So the
+        * cmpxchg64 below only protects one readout.
+        *
+        * We must reread via sched_clock_local() in the retry case on
+        * 32bit as an NMI could use sched_clock_local() via the
+        * tracer and hit between the readout of
+        * the low32bit and the high 32bit portion.
+        */
+       this_clock = sched_clock_local(my_scd);
+       /*
+        * We must enforce atomic readout on 32bit, otherwise the
+        * update on the remote cpu can hit inbetween the readout of
+        * the low32bit and the high 32bit portion.
+        */
+       remote_clock = cmpxchg64(&scd->clock, 0, 0);
+#else
+       /*
+        * On 64bit the read of [my]scd->clock is atomic versus the
+        * update, so we can avoid the above 32bit dance.
+        */
        sched_clock_local(my_scd);
 again:
        this_clock = my_scd->clock;
        remote_clock = scd->clock;
+#endif
 
        /*
         * Use the opportunity that we have both locks