167d0f258f
Andre Wild reported the following warning: WARNING: CPU: 2 PID: 1205 at kernel/cpu.c:240 lockdep_assert_cpus_held+0x4c/0x60 Modules linked in: CPU: 2 PID: 1205 Comm: bash Not tainted 4.13.0-rc2-00022-gfd2b2c57ec20 #10 Hardware name: IBM 2964 N96 702 (z/VM 6.4.0) task: 00000000701d8100 task.stack: 0000000073594000 Krnl PSW : 0704f00180000000 0000000000145e24 (lockdep_assert_cpus_held+0x4c/0x60) ... Call Trace: lockdep_assert_cpus_held+0x42/0x60) stop_machine_cpuslocked+0x62/0xf0 build_all_zonelists+0x92/0x150 numa_zonelist_order_handler+0x102/0x150 proc_sys_call_handler.isra.12+0xda/0x118 proc_sys_write+0x34/0x48 __vfs_write+0x3c/0x178 vfs_write+0xbc/0x1a0 SyS_write+0x66/0xc0 system_call+0xc4/0x2b0 locks held by bash/1205: #0: (sb_writers#4){.+.+.+}, at: vfs_write+0xa6/0x1a0 #1: (zl_order_mutex){+.+...}, at: numa_zonelist_order_handler+0x44/0x150 #2: (zonelists_mutex){+.+...}, at: numa_zonelist_order_handler+0xf4/0x150 Last Breaking-Event-Address: lockdep_assert_cpus_held+0x48/0x60 This can be easily triggered with e.g. echo n > /proc/sys/vm/numa_zonelist_order In commit 3f906ba23689a ("mm/memory-hotplug: switch locking to a percpu rwsem") memory hotplug locking was changed to fix a potential deadlock. This also switched the stop_machine() invocation within build_all_zonelists() to stop_machine_cpuslocked() which now expects that online cpus are locked when being called. This assumption is not true if build_all_zonelists() is being called from numa_zonelist_order_handler(). In order to fix this simply add a mem_hotplug_begin()/mem_hotplug_done() pair to numa_zonelist_order_handler(). Link: http://lkml.kernel.org/r/20170726111738.38768-1-heiko.carstens@de.ibm.com Fixes: 3f906ba23689a ("mm/memory-hotplug: switch locking to a percpu rwsem") Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Reported-by: Andre Wild <wild@linux.vnet.ibm.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.