From: Linus Torvalds <torvalds@linux-foundation.org>
To: Uros Bizjak <ubizjak@gmail.com>
Cc: Nadav Amit <namit@vmware.com>,
"the arch/x86 maintainers" <x86@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Andy Lutomirski <luto@kernel.org>,
Brian Gerst <brgerst@gmail.com>,
Denys Vlasenko <dvlasenk@redhat.com>,
"H . Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Nick Desaulniers <ndesaulniers@google.com>
Subject: Re: [PATCH v2 -tip] x86/percpu: Use C for arch_raw_cpu_ptr()
Date: Tue, 17 Oct 2023 14:53:33 -0700 [thread overview]
Message-ID: <CAHk-=wjSnECwAe+Bi0PD6uods3ZDs8up5OAy-qZKF5OgPLpDiA@mail.gmail.com> (raw)
In-Reply-To: <CAFULd4Z-q4Ot6iyOLo7DkjE=dY3RHXUV+yx6R0iWk=-tZ6ufhQ@mail.gmail.com>
On Tue, 17 Oct 2023 at 14:06, Uros Bizjak <ubizjak@gmail.com> wrote:
>
> But adding the attached patch on top of both patches boots OK.
Funky.
Mind adding a
WARN_ON_ONCE(!active_mm);
to there to give a nice backtrace for the odd NULL case.
That code *is* related to 'current', in how we do
tsk = current;
...
local_irq_disable();
active_mm = tsk->active_mm;
tsk->active_mm = mm;
tsk->mm = mm;
...
activate_mm(active_mm, mm);
...
mmdrop_lazy_tlb(active_mm);
but I don't see how 'active_mm' could *poossibly* be validly NULL
here, and why caching 'current' would matter and change it.
Strange.
Hmm. We do set
tsk->active_mm = NULL;
in copy_mm(), and then we have that odd kernel thread case:
/*
* Are we cloning a kernel thread?
*
* We need to steal a active VM for that..
*/
oldmm = current->mm;
if (!oldmm)
return 0;
but none of this should even matter, because by the time we actually
*schedule* that thread, we'll set active_mm to the right thing.
Can anybody see what's up?
Linus
next prev parent reply other threads:[~2023-10-17 21:53 UTC|newest]
Thread overview: 106+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-10 16:42 [PATCH v2 -tip] x86/percpu: Use C for arch_raw_cpu_ptr() Uros Bizjak
2023-10-10 17:32 ` Linus Torvalds
2023-10-10 18:22 ` Uros Bizjak
2023-10-10 18:25 ` Nadav Amit
2023-10-10 18:42 ` Linus Torvalds
2023-10-10 18:37 ` Linus Torvalds
2023-10-10 18:41 ` Uros Bizjak
2023-10-10 18:52 ` Linus Torvalds
2023-10-11 7:27 ` Uros Bizjak
2023-10-11 7:45 ` Uros Bizjak
2023-10-11 19:40 ` Linus Torvalds
2023-10-11 18:42 ` Uros Bizjak
2023-10-11 19:51 ` Linus Torvalds
2023-10-11 19:52 ` Linus Torvalds
2023-10-11 20:00 ` Uros Bizjak
2023-10-11 22:37 ` Ingo Molnar
2023-10-11 23:15 ` H. Peter Anvin
2023-10-12 1:35 ` Josh Poimboeuf
2023-10-12 6:19 ` Ingo Molnar
2023-10-12 16:08 ` Josh Poimboeuf
2023-10-12 17:59 ` Ingo Molnar
2023-10-12 21:30 ` Josh Poimboeuf
2023-10-13 10:52 ` Ingo Molnar
2023-10-11 7:41 ` Nadav Amit
2023-10-11 19:37 ` Linus Torvalds
2023-10-11 21:32 ` Uros Bizjak
2023-10-11 21:54 ` Linus Torvalds
2023-10-12 15:19 ` Nadav Amit
2023-10-12 16:33 ` Uros Bizjak
2023-10-12 16:55 ` Uros Bizjak
2023-10-12 17:10 ` Linus Torvalds
2023-10-12 17:47 ` Linus Torvalds
2023-10-12 18:01 ` Uros Bizjak
2023-10-13 9:38 ` Uros Bizjak
2023-10-13 11:53 ` Uros Bizjak
2023-10-13 16:38 ` Linus Torvalds
2023-10-12 17:52 ` Uros Bizjak
2023-11-20 9:39 ` Use %a asm operand modifier to obtain %rip-relative addressing Uros Bizjak
2023-10-12 16:56 ` [PATCH v2 -tip] x86/percpu: Use C for arch_raw_cpu_ptr() Linus Torvalds
2023-10-12 17:16 ` Linus Torvalds
2023-10-12 19:32 ` Nadav Amit
2023-10-12 19:40 ` Linus Torvalds
2023-10-16 18:52 ` Uros Bizjak
2023-10-16 19:24 ` Linus Torvalds
2023-10-16 20:35 ` Nadav Amit
2023-10-16 20:59 ` Linus Torvalds
2023-10-16 23:02 ` Linus Torvalds
2023-10-16 23:14 ` Linus Torvalds
2023-10-17 7:23 ` Nadav Amit
2023-10-17 19:00 ` Linus Torvalds
2023-10-17 19:11 ` Uros Bizjak
2023-10-17 21:05 ` Uros Bizjak
2023-10-17 21:53 ` Linus Torvalds [this message]
2023-10-17 22:06 ` Nadav Amit
2023-10-17 22:29 ` Nadav Amit
2023-10-18 7:46 ` Uros Bizjak
2023-10-18 9:04 ` Uros Bizjak
2023-10-18 10:54 ` Nadav Amit
2023-10-18 12:14 ` Uros Bizjak
2023-10-18 13:15 ` Uros Bizjak
2023-10-18 14:46 ` Nadav Amit
2023-10-18 15:17 ` Uros Bizjak
2023-10-18 16:03 ` Nadav Amit
2023-10-18 16:26 ` Linus Torvalds
2023-10-18 17:23 ` Uros Bizjak
2023-10-18 18:11 ` Linus Torvalds
2023-10-18 18:08 ` Uros Bizjak
2023-10-18 18:15 ` Linus Torvalds
2023-10-18 18:26 ` Uros Bizjak
2023-10-18 19:33 ` Uros Bizjak
2023-10-18 20:17 ` Nadav Amit
2023-10-18 20:22 ` Linus Torvalds
2023-10-18 20:34 ` Linus Torvalds
2023-10-18 20:51 ` Uros Bizjak
2023-10-18 21:09 ` Uros Bizjak
2023-10-18 21:10 ` Linus Torvalds
2023-10-18 21:40 ` Uros Bizjak
2023-10-18 22:40 ` Linus Torvalds
2023-10-18 23:06 ` Linus Torvalds
2023-10-19 7:04 ` Uros Bizjak
2023-10-19 16:59 ` Linus Torvalds
2023-10-19 17:21 ` Uros Bizjak
2023-10-19 18:06 ` Linus Torvalds
2023-10-19 18:16 ` Uros Bizjak
2023-10-19 18:49 ` Linus Torvalds
2023-10-19 19:07 ` Linus Torvalds
2023-10-20 7:57 ` Uros Bizjak
2023-10-19 21:04 ` Linus Torvalds
2023-10-19 22:39 ` Linus Torvalds
2023-10-20 8:08 ` Uros Bizjak
2023-10-19 8:44 ` Peter Zijlstra
2023-10-19 8:54 ` Peter Zijlstra
2023-10-19 17:04 ` Linus Torvalds
2023-10-19 18:13 ` Peter Zijlstra
2023-10-19 18:22 ` Linus Torvalds
2023-10-19 18:37 ` Uros Bizjak
2023-10-19 9:07 ` Peter Zijlstra
2023-10-19 9:23 ` Uros Bizjak
2023-10-18 20:42 ` Uros Bizjak
2023-10-19 16:32 ` Uros Bizjak
2023-10-19 17:08 ` Linus Torvalds
2023-10-18 18:29 ` Nadav Amit
2023-10-18 16:12 ` Linus Torvalds
2023-10-18 17:07 ` Uros Bizjak
2023-10-18 18:01 ` Linus Torvalds
2023-10-16 21:09 ` Uros Bizjak
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