linux-kernel - Re: [PATCH] dmaengine: idxd: Fix oops during rmmod on single-CPU platforms

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Message-Id: <171250791415.435162.15364939018197857010.b4-ty@kernel.org>
Date: Sun, 07 Apr 2024 22:08:34 +0530
From: Vinod Koul <vkoul@...nel.org>
To: Dave Jiang <dave.jiang@...el.com>, Fenghua Yu <fenghua.yu@...el.com>
Cc: dmaengine@...r.kernel.org, linux-kernel <linux-kernel@...r.kernel.org>, 
 Terrence Xu <terrence.xu@...el.com>
Subject: Re: [PATCH] dmaengine: idxd: Fix oops during rmmod on single-CPU
 platforms


On Wed, 13 Mar 2024 14:40:31 -0700, Fenghua Yu wrote:
> During the removal of the idxd driver, registered offline callback is
> invoked as part of the clean up process. However, on systems with only
> one CPU online, no valid target is available to migrate the
> perf context, resulting in a kernel oops:
> 
>     BUG: unable to handle page fault for address: 000000000002a2b8
>     #PF: supervisor write access in kernel mode
>     #PF: error_code(0x0002) - not-present page
>     PGD 1470e1067 P4D 0
>     Oops: 0002 [#1] PREEMPT SMP NOPTI
>     CPU: 0 PID: 20 Comm: cpuhp/0 Not tainted 6.8.0-rc6-dsa+ #57
>     Hardware name: Intel Corporation AvenueCity/AvenueCity, BIOS BHSDCRB1.86B.2492.D03.2307181620 07/18/2023
>     RIP: 0010:mutex_lock+0x2e/0x50
>     ...
>     Call Trace:
>     <TASK>
>     __die+0x24/0x70
>     page_fault_oops+0x82/0x160
>     do_user_addr_fault+0x65/0x6b0
>     __pfx___rdmsr_safe_on_cpu+0x10/0x10
>     exc_page_fault+0x7d/0x170
>     asm_exc_page_fault+0x26/0x30
>     mutex_lock+0x2e/0x50
>     mutex_lock+0x1e/0x50
>     perf_pmu_migrate_context+0x87/0x1f0
>     perf_event_cpu_offline+0x76/0x90 [idxd]
>     cpuhp_invoke_callback+0xa2/0x4f0
>     __pfx_perf_event_cpu_offline+0x10/0x10 [idxd]
>     cpuhp_thread_fun+0x98/0x150
>     smpboot_thread_fn+0x27/0x260
>     smpboot_thread_fn+0x1af/0x260
>     __pfx_smpboot_thread_fn+0x10/0x10
>     kthread+0x103/0x140
>     __pfx_kthread+0x10/0x10
>     ret_from_fork+0x31/0x50
>     __pfx_kthread+0x10/0x10
>     ret_from_fork_asm+0x1b/0x30
>     <TASK>
> 
> [...]

Applied, thanks!

[1/1] dmaengine: idxd: Fix oops during rmmod on single-CPU platforms
      commit: f221033f5c24659dc6ad7e5cf18fb1b075f4a8be

Best regards,
-- 
~Vinod