On Mon, 19 Aug 2024 22:24:01 +1000, Michael Ellerman wrote:
> The dtl_access_lock needs to be a rw_sempahore, a sleeping lock, because
> the code calls kmalloc() while holding it, which can sleep:
>
> # echo 1 > /proc/powerpc/vcpudispatch_stats
> BUG: sleeping function called from invalid context at
> include/linux/sched/mm.h:337
> in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 199, name: sh
> preempt_count: 1, expected: 0
> 3 locks held by sh/199:
> #0: c00000000a0743f8 (sb_writers#3){.+.+}-{0:0}, at: vfs_write+0x324/0x438
> #1: c0000000028c7058 (dtl_enable_mutex){+.+.}-{3:3}, at:
> vcpudispatch_stats_write+0xd4/0x5f4
> #2: c0000000028c70b8 (dtl_access_lock){+.+.}-{2:2}, at:
> vcpudispatch_stats_write+0x220/0x5f4
> CPU: 0 PID: 199 Comm: sh Not tainted 6.10.0-rc4 #152
> Hardware name: IBM pSeries (emulated by qemu) POWER9 (raw) 0x4e1202
> 0xf000005 of:SLOF,HEAD hv:linux,kvm pSeries
> Call Trace:
> dump_stack_lvl+0x130/0x148 (unreliable)
> __might_resched+0x174/0x410
> kmem_cache_alloc_noprof+0x340/0x3d0
> alloc_dtl_buffers+0x124/0x1ac
> vcpudispatch_stats_write+0x2a8/0x5f4
> proc_reg_write+0xf4/0x150
> vfs_write+0xfc/0x438
> ksys_write+0x88/0x148
> system_call_exception+0x1c4/0x5a0
> system_call_common+0xf4/0x258
>
> [...]
Applied to powerpc/next.
[1/1] powerpc/pseries: Fix dtl_access_lock to be a rw_semaphore
https://git.kernel.org/powerpc/c/cadae3a45d23aa4f6485938a67cbc47aaaa25e38
cheers
