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 <[email protected]>
Ping?
