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When CONFIG_PREEMPT=y, CONFIG_IPV6=m and CONFIG_SEG6_HMAC=y, seg6_hmac_init() is called during the initialization of the ipv6 module. This causes a subsequent call to smp_processor_id() with preemption enabled, resulting in the following trace. [ 20.451460] BUG: using smp_processor_id() in preemptible [00000000] code: systemd/1 [ 20.452556] caller is debug_smp_processor_id+0x17/0x19 [ 20.453304] CPU: 0 PID: 1 Comm: systemd Not tainted 4.9.0-rc5-00973-g46738b1 #1 [ 20.454406] ffffc9000062fc18 ffffffff813607b2 0000000000000000 ffffffff81a7f782 [ 20.455528] ffffc9000062fc48 ffffffff813778dc 0000000000000000 00000000001dcf98 [ 20.456539] ffffffffa003bd08 ffffffff81af93e0 ffffc9000062fc58 ffffffff81377905 [ 20.456539] Call Trace: [ 20.456539] [<ffffffff813607b2>] dump_stack+0x63/0x7f [ 20.456539] [<ffffffff813778dc>] check_preemption_disabled+0xd1/0xe3 [ 20.456539] [<ffffffff81377905>] debug_smp_processor_id+0x17/0x19 [ 20.460260] [<ffffffffa0061f3b>] seg6_hmac_init+0xfa/0x192 [ipv6] [ 20.460260] [<ffffffffa0061ccc>] seg6_init+0x39/0x6f [ipv6] [ 20.460260] [<ffffffffa006121a>] inet6_init+0x21a/0x321 [ipv6] [ 20.460260] [<ffffffffa0061000>] ? 0xffffffffa0061000 [ 20.460260] [<ffffffff81000457>] do_one_initcall+0x8b/0x115 [ 20.460260] [<ffffffff811328a3>] do_init_module+0x53/0x1c4 [ 20.460260] [<ffffffff8110650a>] load_module+0x1153/0x14ec [ 20.460260] [<ffffffff81106a7b>] SYSC_finit_module+0x8c/0xb9 [ 20.460260] [<ffffffff81106a7b>] ? SYSC_finit_module+0x8c/0xb9 [ 20.460260] [<ffffffff81106abc>] SyS_finit_module+0x9/0xb [ 20.460260] [<ffffffff810014d1>] do_syscall_64+0x62/0x75 [ 20.460260] [<ffffffff816834f0>] entry_SYSCALL64_slow_path+0x25/0x25 Moreover, dst_cache_* functions also call smp_processor_id(), generating a similar trace. This patch uses raw_cpu_ptr() in seg6_hmac_init() rather than this_cpu_ptr() and disable preemption when using dst_cache_* functions. Signed-off-by: David Lebrun <david.lebrun@uclouvain.be> Signed-off-by: David S. Miller <davem@davemloft.net>
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.