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(1) use cpu id from bl31 delivers; (2) sp_el0 should point to kernel address in EL1 mode. On ARM64, kernel uses sp_el0 to store current_thread_info(), we see a problem: when fiq occurs, cpu is EL1 mode but sp_el0 point to userspace address. At this moment, if we read 'current_thread_info()->cpu' or other, it leads an error. We find above situation happens when save/restore cpu context between system mode and user mode under heavy load. Like 'ret_fast_syscall()', kernel restore context of user mode, but fiq occurs before the instruction 'eret', so this causes the above situation. Assembly code: ffffff80080826c8 <ret_fast_syscall>: ...skipping... ffffff80080826fc: d503201f nop ffffff8008082700: d5384100 mrs x0, sp_el0 ffffff8008082704: f9400c00 ldr x0, [x0,#24] ffffff8008082708: d5182000 msr ttbr0_el1, x0 ffffff800808270c: d5033fdf isb ffffff8008082710: f9407ff7 ldr x23, [sp,#248] ffffff8008082714: d5184117 msr sp_el0, x23 ffffff8008082718: d503201f nop ffffff800808271c: d503201f nop ffffff8008082720: d5184035 msr elr_el1, x21 ffffff8008082724: d5184016 msr spsr_el1, x22 ffffff8008082728: a94007e0 ldp x0, x1, [sp] ffffff800808272c: a9410fe2 ldp x2, x3, [sp,#16] ffffff8008082730: a94217e4 ldp x4, x5, [sp,#32] ffffff8008082734: a9431fe6 ldp x6, x7, [sp,#48] ffffff8008082738: a94427e8 ldp x8, x9, [sp,#64] ffffff800808273c: a9452fea ldp x10, x11, [sp,#80] ffffff8008082740: a94637ec ldp x12, x13, [sp,#96] ffffff8008082744: a9473fee ldp x14, x15, [sp,#112] ffffff8008082748: a94847f0 ldp x16, x17, [sp,#128] ffffff800808274c: a9494ff2 ldp x18, x19, [sp,#144] ffffff8008082750: a94a57f4 ldp x20, x21, [sp,#160] ffffff8008082754: a94b5ff6 ldp x22, x23, [sp,#176] ffffff8008082758: a94c67f8 ldp x24, x25, [sp,#192] ffffff800808275c: a94d6ffa ldp x26, x27, [sp,#208] ffffff8008082760: a94e77fc ldp x28, x29, [sp,#224] ffffff8008082764: f9407bfe ldr x30, [sp,#240] ffffff8008082768: 9104c3ff add sp, sp, #0x130 ffffff800808276c: d69f03e0 eret Change-Id: I071e899f8a407764e166ca0403199c9d87d6ce78 Signed-off-by: Joseph Chen <chenjh@rock-chips.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
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.