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[ Upstream commit 833cd3e9ad8360785b6c23c82dd3856df00732d9 ]
Sometimes the system [1] hangs on x86 I/O machine checks. However, the
expected behavior is to reboot the system, as the machine check handler
ultimately triggers a panic(), initiating a reboot in the last step.
The root cause is that sometimes the panic() is blocked when
drm_fb_helper_damage() invoking schedule_work() to flush the frame buffer.
This occurs during the process of flushing all messages to the frame
buffer driver as shown in the following call trace:
Machine check occurs [2]:
panic()
console_flush_on_panic()
console_flush_all()
console_emit_next_record()
con->write()
vt_console_print()
hide_cursor()
vc->vc_sw->con_cursor()
fbcon_cursor()
ops->cursor()
bit_cursor()
soft_cursor()
info->fbops->fb_imageblit()
drm_fbdev_generic_defio_imageblit()
drm_fb_helper_damage_area()
drm_fb_helper_damage()
schedule_work() // <--- blocked here
...
emergency_restart() // wasn't invoked, so no reboot.
During panic(), except the panic CPU, all the other CPUs are stopped.
In schedule_work(), the panic CPU requires the lock of worker_pool to
queue the work on that pool, while the lock may have been token by some
other stopped CPU. So schedule_work() is blocked.
Additionally, during a panic(), since there is no opportunity to execute
any scheduled work, it's safe to fix this issue by skipping schedule_work()
on 'oops_in_progress' in drm_fb_helper_damage().
[1] Enable the kernel option CONFIG_FRAMEBUFFER_CONSOLE,
CONFIG_DRM_FBDEV_EMULATION, and boot with the 'console=tty0'
kernel command line parameter.
[2] Set 'panic_timeout' to a non-zero value before calling panic().
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Reported-by: Yudong Wang <yudong.wang@intel.com>
Tested-by: Yudong Wang <yudong.wang@intel.com>
Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240703141737.75378-1-qiuxu.zhuo@intel.com
Signed-off-by: Maarten Lankhorst,,, <maarten.lankhorst@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.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.