From: Breno Leitao <leitao@debian.org>
To: Amit Shah <amit@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Sungho Bae <baver.bae@lge.com>
Cc: virtualization@lists.linux.dev, linux-kernel@vger.kernel.org,
kernel-team@meta.com
Subject: Re: [PATCH] virtio_console: allocate the port_buffer with the caller's gfp
Date: Tue, 18 Aug 2026 02:06:37 -0700 [thread overview]
Message-ID: <aoQggUaBZC9GeY1Y@gmail.com> (raw)
In-Reply-To: <20260810-serial-v1-1-abbe51602c13@debian.org>
On Mon, Aug 10, 2026 at 09:40:00AM -0700, Breno Leitao wrote:
> put_chars() runs from the hvc console write path with preemption
> disabled, so it asks alloc_buf() for GFP_ATOMIC. Only the data buffer
> gets it: the struct port_buffer itself keeps the GFP_KERNEL default, so
> the allocation can enter direct reclaim and sleep. A write to /dev/kmsg
> on a CONFIG_DEBUG_ATOMIC_SLEEP kernel splats:
>
> BUG: sleeping function called from invalid context at ./include/linux/sched/mm.h:320
> in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 1, name: virtme-ng-init
> preempt_count: 1, expected: 0
> Preemption disabled at:
> [<ffffffff813fd90d>] vprintk_emit+0x17d/0x510
> Call Trace:
> <TASK>
> dump_stack_lvl+0x69/0xa0
> __might_resched+0x37a/0x4d0
> __kmalloc_cache_noprof+0x94/0x5f0
> put_chars+0x209/0x3e0
> hvc_console_print+0x234/0x640
> console_flush_all+0x4fc/0x950
> console_unlock+0xbf/0x1b0
> vprintk_emit+0x312/0x510
> devkmsg_emit+0xba/0x110
> devkmsg_write+0x21b/0x2e0
> vfs_write+0x4dc/0x9d0
> ksys_write+0x108/0x1e0
> do_syscall_64+0xfa/0x460
> </TASK>
>
> Pass gfp on to that allocation too.
>
> Fixes: fc220d6be3c7 ("virtio_console: refactor __send_to_port() buffer ownership")
> Signed-off-by: Breno Leitao <leitao@debian.org>
Ping?
prev parent reply other threads:[~2026-08-18 9:06 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-10 16:40 [PATCH] virtio_console: allocate the port_buffer with the caller's gfp Breno Leitao
2026-08-18 9:06 ` Breno Leitao [this message]
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