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Commit1ec9dd80be("MIPS: CPS: Detect CPUs in secondary clusters") added a check in cps_boot_secondary() that the secondary being booted is in the same cluster as the CPU running this code. This check is performed using current_cpu_data without disabling preemption. As such when CONFIG_PREEMPT=y, a BUG is triggered: [ 57.991693] BUG: using smp_processor_id() in preemptible [00000000] code: hotplug/1749 <snip> [ 58.063077] Call Trace: [ 58.065842] [<8040cdb4>] show_stack+0x84/0x114 [ 58.070830] [<80b11b38>] dump_stack+0xf8/0x140 [ 58.075796] [<8079b12c>] check_preemption_disabled+0xec/0x118 [ 58.082204] [<80415110>] cps_boot_secondary+0x84/0x44c [ 58.087935] [<80413a14>] __cpu_up+0x34/0x98 [ 58.092624] [<80434240>] bringup_cpu+0x38/0x114 [ 58.097680] [<80434af0>] cpuhp_invoke_callback+0x168/0x8f0 [ 58.103801] [<804362d0>] _cpu_up+0x154/0x1c8 [ 58.108565] [<804363dc>] do_cpu_up+0x98/0xa8 [ 58.113333] [<808261f8>] device_online+0x84/0xc0 [ 58.118481] [<80826294>] online_store+0x60/0x98 [ 58.123562] [<8062261c>] kernfs_fop_write+0x158/0x1d4 [ 58.129196] [<805a2ae4>] __vfs_write+0x4c/0x168 [ 58.134247] [<805a2dc8>] vfs_write+0xe0/0x190 [ 58.139095] [<805a2fe0>] SyS_write+0x68/0xc4 [ 58.143854] [<80415d58>] syscall_common+0x34/0x58 In reality we don't currently support running the kernel on CPUs not in cluster 0, so the answer to cpu_cluster(¤t_cpu_data) will always be 0, even if this task being preempted and continues running on a different CPU. Regardless, the BUG should not be triggered, so fix this by switching to raw_current_cpu_data. When multicluster support lands upstream this check will need removing or changing anyway. Fixes:1ec9dd80be("MIPS: CPS: Detect CPUs in secondary clusters") Signed-off-by: Matt Redfearn <matt.redfearn@mips.com> Reviewed-by: Paul Burton <paul.burton@mips.com> CC: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/17563/ Signed-off-by: James Hogan <jhogan@kernel.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.