Re: [PATCH] cpu/cacheinfo: Fix teardown path

[Borislav Petkov]

On Mon, Jul 27, 2015 at 09:58:05AM +0200, Borislav Petkov wrote:
> Philip MÃller reported a hang when booting 32-bit 4.1 kernel on an AMD
> box. A fragment of the splat was enough to pinpoint the issue:

Bah, this goes to Greg and not to tip. Anyway, here's a version with
updated tags.

Greg, please queue for 4.2 as it fixes a hang.

Thanks.

---
From: Borislav Petkov <bp@xxxxxxx>
Date: Mon, 27 Jul 2015 08:36:27 +0200
Subject: [PATCH] cpu/cacheinfo: Fix teardown path
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Philip MÃller reported a hang when booting 32-bit 4.1 kernel on an AMD
box. A fragment of the splat was enough to pinpoint the issue:

  task: f58e0000 ti: f58e8000 task.ti: f58e800
  EIP: 0060:[<c135a903>] EFLAGS: 00010206 CPU: 0
  EIP is at free_cache_attributes+0x83/0xd0
  EAX: 00000001 EBX: f589d46c ECX: 00000090 EDX: 360c2000
  ESI: 00000000 EDI: c1724a80 EBP: f58e9ec0 ESP: f58e9ea0
   DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
  CR0: 8005003b CR2: 000000ac CR3: 01731000 CR4: 000006d0

cache_shared_cpu_map_setup() did check sibling CPUs cacheinfo descriptor
while the respective teardown path cache_shared_cpu_map_remove() didn't.
Fix that.

>From tglx's version: to be on the safe side, move the cacheinfo
descriptor check to free_cache_attributes(), thus cleaning up the
hotplug path a little and making this even more robust.

Reported-and-tested-by: Philip MÃller <philm@xxxxxxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Acked-by: Sudeep Holla <sudeep.holla@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 4.1
Cc: Andre Przywara <andre.przywara@xxxxxxx>
Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
Cc: manjaro-dev@xxxxxxxxxxx
Cc: Philip MÃller <philm@xxxxxxxxxxx>
Link: https://lkml.kernel.org/r/55B47BB8.6080202@xxxxxxxxxxx
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
---
 drivers/base/cacheinfo.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
index 764280a91776..e9fd32e91668 100644
--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -148,7 +148,11 @@ static void cache_shared_cpu_map_remove(unsigned int cpu)
 
 			if (sibling == cpu) /* skip itself */
 				continue;
+
 			sib_cpu_ci = get_cpu_cacheinfo(sibling);
+			if (!sib_cpu_ci->info_list)
+				continue;
+
 			sib_leaf = sib_cpu_ci->info_list + index;
 			cpumask_clear_cpu(cpu, &sib_leaf->shared_cpu_map);
 			cpumask_clear_cpu(sibling, &this_leaf->shared_cpu_map);
@@ -159,6 +163,9 @@ static void cache_shared_cpu_map_remove(unsigned int cpu)
 
 static void free_cache_attributes(unsigned int cpu)
 {
+	if (!per_cpu_cacheinfo(cpu))
+		return;
+
 	cache_shared_cpu_map_remove(cpu);
 
 	kfree(per_cpu_cacheinfo(cpu));
@@ -514,8 +521,7 @@ static int cacheinfo_cpu_callback(struct notifier_block *nfb,
 		break;
 	case CPU_DEAD:
 		cache_remove_dev(cpu);
-		if (per_cpu_cacheinfo(cpu))
-			free_cache_attributes(cpu);
+		free_cache_attributes(cpu);
 		break;
 	}
 	return notifier_from_errno(rc);
-- 
2.5.0.rc2.28.g6003e7f

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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