linux-kernel - powerpc/hugetlb: BUG: using smp_processor

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Date:	Fri, 17 Jan 2014 13:23:50 +0400
From:	Nikita Yushchenko <nyushchenko@....rtsoft.ru>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Cc:	Alexey Lugovskoy <lugovskoy@....rtsoft.ru>
Subject: powerpc/hugetlb: BUG: using smp_processor_id() in preemptible

Hi

While running LTP hugeltb tests on freescale powerpc board, I'm getting 

[ 7253.637591] BUG: using smp_processor_id() in preemptible [00000000 00000000]
code: hugemmap01/9048
[ 7253.637601] caller is free_hugepd_range.constprop.25+0x88/0x1a8
[ 7253.637605] CPU: 1 PID: 9048 Comm: hugemmap01 Not tainted 3.10.20-rt14+ #114
[ 7253.637606] Call Trace:
[ 7253.637617] [cb049d80] [c0007ea4] show_stack+0x4c/0x168 (unreliable)
[ 7253.637624] [cb049dc0] [c031c674] debug_smp_processor_id+0x114/0x134
[ 7253.637628] [cb049de0] [c0016d28] free_hugepd_range.constprop.25+0x88/0x1a8
[ 7253.637632] [cb049e00] [c001711c] hugetlb_free_pgd_range+0x6c/0x168
[ 7253.637639] [cb049e40] [c0117408] free_pgtables+0x12c/0x150
[ 7253.637646] [cb049e70] [c011ce38] unmap_region+0xa0/0x11c
[ 7253.637671] [cb049ef0] [c011f03c] do_munmap+0x224/0x3bc
[ 7253.637676] [cb049f20] [c011f2e0] vm_munmap+0x38/0x5c
[ 7253.637682] [cb049f40] [c000ef88] ret_from_syscall+0x0/0x3c
[ 7253.637686] --- Exception: c01 at 0xff16004

This is on 3.10 based kernel but looks like code in question did not change
since then.

Immediate reason of this dump is usage of smp_processor_id() in hugepd_free(),
which is executed in preemptible context on this path.

Perhaps need to add preempt_disable() / preempt_enable() somewhere.
But what is the proper location for these?


Nikita
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