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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Wed, 15 May 2019 08:46:04 +0100 Received: from b03ledav005.gho.boulder.ibm.com (b03ledav005.gho.boulder.ibm.com [9.17.130.236]) by b03cxnp08027.gho.boulder.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x4F7k3vs6619434 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 15 May 2019 07:46:03 GMT Received: from b03ledav005.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3C30ABE053; Wed, 15 May 2019 07:46:03 +0000 (GMT) Received: from b03ledav005.gho.boulder.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id EBCEEBE051; Wed, 15 May 2019 07:46:02 +0000 (GMT) Received: from sofia.ibm.com (unknown [9.124.35.248]) by b03ledav005.gho.boulder.ibm.com (Postfix) with ESMTP; Wed, 15 May 2019 07:46:02 +0000 (GMT) Received: by sofia.ibm.com (Postfix, from userid 1000) id 351052E3579; Wed, 15 May 2019 13:15:59 +0530 (IST) From: "Gautham R. Shenoy" To: Paul Mackerras , Nicholas Piggin , Michael Ellerman , "Aneesh Kumar K.V" Subject: [PATCH v3] powerpc/pseries: Fix cpu_hotplug_lock acquisition in resize_hpt() Date: Wed, 15 May 2019 13:15:52 +0530 X-Mailer: git-send-email 1.8.3.1 X-TM-AS-GCONF: 00 x-cbid: 19051507-0036-0000-0000-00000ABA5ECD X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00011100; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000285; SDB=6.01203565; UDB=6.00631764; IPR=6.00984492; MB=3.00026899; MTD=3.00000008; XFM=3.00000015; UTC=2019-05-15 07:46:06 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19051507-0037-0000-0000-00004BCB7361 Message-Id: <1557906352-29048-1-git-send-email-ego@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:, , definitions=2019-05-15_05:, , signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1905150050 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Gautham R. Shenoy" , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" From: "Gautham R. Shenoy" The calls to arch_add_memory()/arch_remove_memory() are always made with the read-side cpu_hotplug_lock acquired via memory_hotplug_begin(). On pSeries, arch_add_memory()/arch_remove_memory() eventually call resize_hpt() which in turn calls stop_machine() which acquires the read-side cpu_hotplug_lock again, thereby resulting in the recursive acquisition of this lock. Lockdep complains as follows in these code-paths. swapper/0/1 is trying to acquire lock: (____ptrval____) (cpu_hotplug_lock.rw_sem){++++}, at: stop_machine+0x2c/0x60 but task is already holding lock: (____ptrval____) (cpu_hotplug_lock.rw_sem){++++}, at: mem_hotplug_begin+0x20/0x50 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(cpu_hotplug_lock.rw_sem); lock(cpu_hotplug_lock.rw_sem); *** DEADLOCK *** May be due to missing lock nesting notation 3 locks held by swapper/0/1: #0: (____ptrval____) (&dev->mutex){....}, at: __driver_attach+0x12c/0x1b0 #1: (____ptrval____) (cpu_hotplug_lock.rw_sem){++++}, at: mem_hotplug_begin+0x20/0x50 #2: (____ptrval____) (mem_hotplug_lock.rw_sem){++++}, at: percpu_down_write+0x54/0x1a0 stack backtrace: CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.0.0-rc5-58373-gbc99402235f3-dirty #166 Call Trace: [c0000000feb03150] [c000000000e32bd4] dump_stack+0xe8/0x164 (unreliable) [c0000000feb031a0] [c00000000020d6c0] __lock_acquire+0x1110/0x1c70 [c0000000feb03320] [c00000000020f080] lock_acquire+0x240/0x290 [c0000000feb033e0] [c00000000017f554] cpus_read_lock+0x64/0xf0 [c0000000feb03420] [c00000000029ebac] stop_machine+0x2c/0x60 [c0000000feb03460] [c0000000000d7f7c] pseries_lpar_resize_hpt+0x19c/0x2c0 [c0000000feb03500] [c0000000000788d0] resize_hpt_for_hotplug+0x70/0xd0 [c0000000feb03570] [c000000000e5d278] arch_add_memory+0x58/0xfc [c0000000feb03610] [c0000000003553a8] devm_memremap_pages+0x5e8/0x8f0 [c0000000feb036c0] [c0000000009c2394] pmem_attach_disk+0x764/0x830 [c0000000feb037d0] [c0000000009a7c38] nvdimm_bus_probe+0x118/0x240 [c0000000feb03860] [c000000000968500] really_probe+0x230/0x4b0 [c0000000feb038f0] [c000000000968aec] driver_probe_device+0x16c/0x1e0 [c0000000feb03970] [c000000000968ca8] __driver_attach+0x148/0x1b0 [c0000000feb039f0] [c0000000009650b0] bus_for_each_dev+0x90/0x130 [c0000000feb03a50] [c000000000967dd4] driver_attach+0x34/0x50 [c0000000feb03a70] [c000000000967068] bus_add_driver+0x1a8/0x360 [c0000000feb03b00] [c00000000096a498] driver_register+0x108/0x170 [c0000000feb03b70] [c0000000009a7400] __nd_driver_register+0xd0/0xf0 [c0000000feb03bd0] [c00000000128aa90] nd_pmem_driver_init+0x34/0x48 [c0000000feb03bf0] [c000000000010a10] do_one_initcall+0x1e0/0x45c [c0000000feb03cd0] [c00000000122462c] kernel_init_freeable+0x540/0x64c [c0000000feb03db0] [c00000000001110c] kernel_init+0x2c/0x160 [c0000000feb03e20] [c00000000000bed4] ret_from_kernel_thread+0x5c/0x68 Fix this issue by 1) Requiring all the calls to pseries_lpar_resize_hpt() be made with cpu_hotplug_lock held. 2) In pseries_lpar_resize_hpt() invoke stop_machine_cpuslocked() as a consequence of 1) 3) To satisfy 1), in hpt_order_set(), call mmu_hash_ops.resize_hpt() with cpu_hotplug_lock held. Reported-by: Aneesh Kumar K.V Signed-off-by: Gautham R. Shenoy --- v2 -> v3 : Updated the comment for pseries_lpar_resize_hpt() Updated the commit-log with the full backtrace. v1 -> v2 : Rebased against powerpc/next instead of linux/master arch/powerpc/mm/book3s64/hash_utils.c | 9 ++++++++- arch/powerpc/platforms/pseries/lpar.c | 8 ++++++-- 2 files changed, 14 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c index 919a861..d07fcafd 100644 --- a/arch/powerpc/mm/book3s64/hash_utils.c +++ b/arch/powerpc/mm/book3s64/hash_utils.c @@ -38,6 +38,7 @@ #include #include #include +#include #include #include @@ -1928,10 +1929,16 @@ static int hpt_order_get(void *data, u64 *val) static int hpt_order_set(void *data, u64 val) { + int ret; + if (!mmu_hash_ops.resize_hpt) return -ENODEV; - return mmu_hash_ops.resize_hpt(val); + cpus_read_lock(); + ret = mmu_hash_ops.resize_hpt(val); + cpus_read_unlock(); + + return ret; } DEFINE_DEBUGFS_ATTRIBUTE(fops_hpt_order, hpt_order_get, hpt_order_set, "%llu\n"); diff --git a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c index 1034ef1..557d592 100644 --- a/arch/powerpc/platforms/pseries/lpar.c +++ b/arch/powerpc/platforms/pseries/lpar.c @@ -859,7 +859,10 @@ static int pseries_lpar_resize_hpt_commit(void *data) return 0; } -/* Must be called in user context */ +/* + * Must be called in process context. The caller must hold the + * cpus_lock. + */ static int pseries_lpar_resize_hpt(unsigned long shift) { struct hpt_resize_state state = { @@ -913,7 +916,8 @@ static int pseries_lpar_resize_hpt(unsigned long shift) t1 = ktime_get(); - rc = stop_machine(pseries_lpar_resize_hpt_commit, &state, NULL); + rc = stop_machine_cpuslocked(pseries_lpar_resize_hpt_commit, + &state, NULL); t2 = ktime_get(); -- 1.9.4