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.
Jens Axboe
authored
If someone removes a node from a list, and then later adds it back to a list, we can have invalid data in ->next. This can cause all sorts of issues. One such use case is the IORING_OP_POLL_ADD command, which will do just that if we race and get woken twice without any pending events. This is a pretty rare case, but can happen under extreme loads. Dan reports that he saw the following crash: BUG: kernel NULL pointer dereference, address: 0000000000000000 PGD d283ce067 P4D d283ce067 PUD e5ca04067 PMD 0 Oops: 0002 [#1] SMP CPU: 17 PID: 10726 Comm: tao:fast-fiber Kdump: loaded Not tainted 5.2.9-02851-gac7bc042d2d1 #116 Hardware name: Quanta Twin Lakes MP/Twin Lakes Passive MP, BIOS F09_3A17 05/03/2019 RIP: 0010:io_wqe_enqueue+0x3e/0xd0 Code: 34 24 74 55 8b 47 58 48 8d 6f 50 85 c0 74 50 48 89 df e8 35 7c 75 00 48 83 7b 08 00 48 8b 14 24 0f 84 84 00 00 00 48 8b 4b 10 <48> 89 11 48 89 53 10 83 63 20 fe 48 89 c6 48 89 df e8 0c 7a 75 00 RSP: 0000:ffffc90006858a08 EFLAGS: ...