lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <1305833911-7717-12-git-send-email-vgoyal@redhat.com>
Date:	Thu, 19 May 2011 15:38:29 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	linux-kernel@...r.kernel.org, jaxboe@...ionio.com, axboe@...nel.dk
Cc:	dpshah@...gle.com, vgoyal@...hat.com
Subject: [PATCH 11/13] blk-cgroup: Make 64bit per cpu stats safe on 32bit arch

Some of the stats are 64bit and updation will be non atomic on 32bit
architecture. Use sequence counters on 32bit arch to make reading
of stats safe.

Signed-off-by: Vivek Goyal <vgoyal@...hat.com>
---
 block/blk-cgroup.c |   27 ++++++++++++++++++++++-----
 block/blk-cgroup.h |    2 ++
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 34bfcef..3622518e 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -400,14 +400,25 @@ void blkiocg_update_dispatch_stats(struct blkio_group *blkg,
 				uint64_t bytes, bool direction, bool sync)
 {
 	struct blkio_group_stats_cpu *stats_cpu;
+	unsigned long flags;
+
+	/*
+	 * Disabling interrupts to provide mutual exclusion between two
+	 * writes on same cpu. It probably is not needed for 64bit. Not
+	 * optimizing that case yet.
+	 */
+	local_irq_save(flags);
 
 	stats_cpu = this_cpu_ptr(blkg->stats_cpu);
 
+	u64_stats_update_begin(&stats_cpu->syncp);
 	stats_cpu->sectors += bytes >> 9;
 	blkio_add_stat(stats_cpu->stat_arr_cpu[BLKIO_STAT_CPU_SERVICED],
 			1, direction, sync);
 	blkio_add_stat(stats_cpu->stat_arr_cpu[BLKIO_STAT_CPU_SERVICE_BYTES],
 			bytes, direction, sync);
+	u64_stats_update_end(&stats_cpu->syncp);
+	local_irq_restore(flags);
 }
 EXPORT_SYMBOL_GPL(blkiocg_update_dispatch_stats);
 
@@ -622,15 +633,21 @@ static uint64_t blkio_read_stat_cpu(struct blkio_group *blkg,
 {
 	int cpu;
 	struct blkio_group_stats_cpu *stats_cpu;
-	uint64_t val = 0;
+	u64 val = 0, tval;
 
 	for_each_possible_cpu(cpu) {
+		unsigned int start;
 		stats_cpu  = per_cpu_ptr(blkg->stats_cpu, cpu);
 
-		if (type == BLKIO_STAT_CPU_SECTORS)
-			val += stats_cpu->sectors;
-		else
-			val += stats_cpu->stat_arr_cpu[type][sub_type];
+		do {
+			start = u64_stats_fetch_begin(&stats_cpu->syncp);
+			if (type == BLKIO_STAT_CPU_SECTORS)
+				tval = stats_cpu->sectors;
+			else
+				tval = stats_cpu->stat_arr_cpu[type][sub_type];
+		} while(u64_stats_fetch_retry(&stats_cpu->syncp, start));
+
+		val += tval;
 	}
 
 	return val;
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index fd730a2..2622267 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -14,6 +14,7 @@
  */
 
 #include <linux/cgroup.h>
+#include <linux/u64_stats_sync.h>
 
 enum blkio_policy_id {
 	BLKIO_POLICY_PROP = 0,		/* Proportional Bandwidth division */
@@ -154,6 +155,7 @@ struct blkio_group_stats {
 struct blkio_group_stats_cpu {
 	uint64_t sectors;
 	uint64_t stat_arr_cpu[BLKIO_STAT_CPU_NR][BLKIO_STAT_TOTAL];
+	struct u64_stats_sync syncp;
 };
 
 struct blkio_group {
-- 
1.7.4.4

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ