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7b4ea9456d
This reverts commit 8bb9bf242d.
It seems the vmalloc page tables aren't always preallocated in all
situations, because Jason Donenfeld reports an oops with this commit:
BUG: unable to handle page fault for address: ffffe8ffffd00608
#PF: supervisor read access in kernel mode
#PF: error_code(0x0000) - not-present page
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP
CPU: 2 PID: 22 Comm: kworker/2:0 Not tainted 5.8.0+ #154
RIP: process_one_work+0x2c/0x2d0
Code: 41 56 41 55 41 54 55 48 89 f5 53 48 89 fb 48 83 ec 08 48 8b 06 4c 8b 67 40 49 89 c6 45 30 f6 a8 04 b8 00 00 00 00 4c 0f 44 f0 <49> 8b 46 08 44 8b a8 00 01 05
Call Trace:
worker_thread+0x4b/0x3b0
? rescuer_thread+0x360/0x360
kthread+0x116/0x140
? __kthread_create_worker+0x110/0x110
ret_from_fork+0x1f/0x30
CR2: ffffe8ffffd00608
and that page fault address is right in that vmalloc space, and we
clearly don't have a PGD/P4D entry for it.
Looking at the "Code:" line, the actual fault seems to come from the
'pwq->wq' dereference at the top of the process_one_work() function:
struct pool_workqueue *pwq = get_work_pwq(work);
struct worker_pool *pool = worker->pool;
bool cpu_intensive = pwq->wq->flags & WQ_CPU_INTENSIVE;
so 'struct pool_workqueue *pwq' is the allocation that hasn't been
synchronized across CPUs.
Just revert for now, while Joerg figures out the cause.
Reported-and-bisected-by: Jason A. Donenfeld <Jason@zx2c4.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.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.