278e483dc7
commit 38fa3206bf441911258e5001ac8b6738693f8d82 upstream. While reboot the system by sysrq, the following bug will be occur. BUG: sleeping function called from invalid context at kernel/locking/semaphore.c:90 in_atomic(): 0, irqs_disabled(): 128, non_block: 0, pid: 10052, name: rc.shutdown CPU: 3 PID: 10052 Comm: rc.shutdown Tainted: G W O 5.10.0 #1 Call trace: dump_backtrace+0x0/0x1c8 show_stack+0x18/0x28 dump_stack+0xd0/0x110 ___might_sleep+0x14c/0x160 __might_sleep+0x74/0x88 down_interruptible+0x40/0x118 virt_efi_reset_system+0x3c/0xd0 efi_reboot+0xd4/0x11c machine_restart+0x60/0x9c emergency_restart+0x1c/0x2c sysrq_handle_reboot+0x1c/0x2c __handle_sysrq+0xd0/0x194 write_sysrq_trigger+0xbc/0xe4 proc_reg_write+0xd4/0xf0 vfs_write+0xa8/0x148 ksys_write+0x6c/0xd8 __arm64_sys_write+0x18/0x28 el0_svc_common.constprop.3+0xe4/0x16c do_el0_svc+0x1c/0x2c el0_svc+0x20/0x30 el0_sync_handler+0x80/0x17c el0_sync+0x158/0x180 The reason for this problem is that irq has been disabled in machine_restart() and then it calls down_interruptible() in virt_efi_reset_system(), which would occur sleep in irq context, it is dangerous! Commit 99409b935c9a("locking/semaphore: Add might_sleep() to down_*() family") add might_sleep() in down_interruptible(), so the bug info is here. down_trylock() can solve this problem, cause there is no might_sleep. -------- Cc: <stable@vger.kernel.org> Signed-off-by: Zhang Jianhua <chris.zjh@huawei.com> Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.
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.