[PATCH RT 18/25][RFC 3.0.23-rt39-rc1] net: u64_stat: Protect seqcount

[Steven Rostedt]

From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

On RT we must prevent that the writer gets preempted inside the write
section. Otherwise a preempting reader might spin forever.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: stable-rt@xxxxxxxxxxxxxxx
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 include/linux/u64_stats_sync.h |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/include/linux/u64_stats_sync.h b/include/linux/u64_stats_sync.h
index 8da8c4e..b39549f 100644
--- a/include/linux/u64_stats_sync.h
+++ b/include/linux/u64_stats_sync.h
@@ -70,6 +70,7 @@ struct u64_stats_sync {
 static inline void u64_stats_update_begin(struct u64_stats_sync *syncp)
 {
 #if BITS_PER_LONG==32 && defined(CONFIG_SMP)
+	preempt_disable_rt();
 	write_seqcount_begin(&syncp->seq);
 #endif
 }
@@ -78,6 +79,7 @@ static inline void u64_stats_update_end(struct u64_stats_sync *syncp)
 {
 #if BITS_PER_LONG==32 && defined(CONFIG_SMP)
 	write_seqcount_end(&syncp->seq);
+	preempt_enable_rt();
 #endif
 }
 
-- 
1.7.8.3


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