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Commit 33d91f00 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

net: u64_stats_fetch_begin_bh() and u64_stats_fetch_retry_bh() 



- Must disable preemption in case of 32bit UP in u64_stats_fetch_begin()
and u64_stats_fetch_retry()

- Add new u64_stats_fetch_begin_bh() and u64_stats_fetch_retry_bh() for
network usage, disabling BH on 32bit UP only.

Signed-off-by: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7a9b2d59

include/linux/u64_stats_sync.h

+44 −15
Original line number Diff line number Diff line
@@ -27,6 +27,9 @@ 
 *    (On UP, there is no seqcount_t protection, a reader allowing interrupts could

 *     read partial values)

 *

 * 7) For softirq uses, readers can use u64_stats_fetch_begin_bh() and

 *    u64_stats_fetch_retry_bh() helpers

 *

 * Usage :

 *

 * Stats producer (writer) should use following template granted it already got
@@ -58,54 +61,80 @@ 
 */

#include <linux/seqlock.h>



#if BITS_PER_LONG==32 && defined(CONFIG_SMP)

struct u64_stats_sync {

#if BITS_PER_LONG==32 && defined(CONFIG_SMP)

	seqcount_t	seq;

#endif

};



static void inline u64_stats_update_begin(struct u64_stats_sync *syncp)

{

#if BITS_PER_LONG==32 && defined(CONFIG_SMP)

	write_seqcount_begin(&syncp->seq);

#endif

}



static void inline u64_stats_update_end(struct u64_stats_sync *syncp)

{

#if BITS_PER_LONG==32 && defined(CONFIG_SMP)

	write_seqcount_end(&syncp->seq);

#endif

}



static unsigned int inline u64_stats_fetch_begin(const struct u64_stats_sync *syncp)

{

#if BITS_PER_LONG==32 && defined(CONFIG_SMP)

	return read_seqcount_begin(&syncp->seq);

#else

#if BITS_PER_LONG==32

	preempt_disable();

#endif

	return 0;

#endif

}



static bool inline u64_stats_fetch_retry(const struct u64_stats_sync *syncp,

					 unsigned int start)

{

#if BITS_PER_LONG==32 && defined(CONFIG_SMP)

	return read_seqcount_retry(&syncp->seq, start);

}



#else

struct u64_stats_sync {

};



static void inline u64_stats_update_begin(struct u64_stats_sync *syncp)

{

}



static void inline u64_stats_update_end(struct u64_stats_sync *syncp)

{

#if BITS_PER_LONG==32

	preempt_enable();

#endif

	return false;

#endif

}



static unsigned int inline u64_stats_fetch_begin(const struct u64_stats_sync *syncp)

/*

 * In case softirq handlers can update u64 counters, readers can use following helpers

 * - SMP 32bit arches use seqcount protection, irq safe.

 * - UP 32bit must disable BH.

 * - 64bit have no problem atomically reading u64 values, irq safe.

 */

static unsigned int inline u64_stats_fetch_begin_bh(const struct u64_stats_sync *syncp)

{

#if BITS_PER_LONG==32 && defined(CONFIG_SMP)

	return read_seqcount_begin(&syncp->seq);

#else

#if BITS_PER_LONG==32

	local_bh_disable();

#endif

	return 0;

#endif

}



static bool inline u64_stats_fetch_retry(const struct u64_stats_sync *syncp,

static bool inline u64_stats_fetch_retry_bh(const struct u64_stats_sync *syncp,

					 unsigned int start)

{

#if BITS_PER_LONG==32 && defined(CONFIG_SMP)

	return read_seqcount_retry(&syncp->seq, start);

#else

#if BITS_PER_LONG==32

	local_bh_enable();

#endif

	return false;

}

#endif

}



#endif /* _LINUX_U64_STATS_SYNC_H */