| Message ID | 20181101052105.17973-1-mpe@ellerman.id.au (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | c8b00bb742dd036388f37d019dbb9db177f3e66c |
| Headers | show |
| Series | powerpc/mm/64s: Fix preempt warning in slb_allocate_kernel() | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/apply_patch | success | next/apply_patch Successfully applied |
| snowpatch_ozlabs/checkpatch | success | Test checkpatch on branch next |
| snowpatch_ozlabs/build-ppc64le | success | Test build-ppc64le on branch next |
| snowpatch_ozlabs/build-ppc64be | success | Test build-ppc64be on branch next |
| snowpatch_ozlabs/build-ppc64e | success | Test build-ppc64e on branch next |
| snowpatch_ozlabs/build-ppc32 | success | Test build-ppc32 on branch next |
On Thu, 2018-11-01 at 05:21:05 UTC, Michael Ellerman wrote: > With preempt enabled we see warnings in do_slb_fault(): > > BUG: using smp_processor_id() in preemptible [00000000] code: kworker/u33:0/98 > futex hash table entries: 4096 (order: 3, 524288 bytes) > caller is do_slb_fault+0x204/0x230 > CPU: 5 PID: 98 Comm: kworker/u33:0 Not tainted 4.19.0-rc3-gcc-7.3.1-00022-g1936f094e164 #138 > Call Trace: > dump_stack+0xb4/0x104 (unreliable) > check_preemption_disabled+0x148/0x150 > do_slb_fault+0x204/0x230 > data_access_slb_common+0x138/0x180 > > This is caused by the get_paca() in slb_allocate_kernel(), which > includes a call to debug_smp_processor_id(). > > slb_allocate_kernel() can only be called from do_slb_fault(), and in > that path interrupts are hard disabled and so we can't be preempted, > but we can't update the preempt flags (in thread_info) because that > could cause an SLB fault. > > So just use local_paca which is safe and doesn't cause the warning. > > Fixes: 48e7b7695745 ("powerpc/64s/hash: Convert SLB miss handlers to C") > Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Applied to powerpc fixes. https://git.kernel.org/powerpc/c/c8b00bb742dd036388f37d019dbb9d cheers
diff --git a/arch/powerpc/mm/slb.c b/arch/powerpc/mm/slb.c index c3fdf2969d9f..2f5c0a10fac1 100644 --- a/arch/powerpc/mm/slb.c +++ b/arch/powerpc/mm/slb.c @@ -715,7 +715,7 @@ static long slb_allocate_kernel(unsigned long ea, unsigned long id) return -EFAULT; if (ea < H_VMALLOC_END) - flags = get_paca()->vmalloc_sllp; + flags = local_paca->vmalloc_sllp; else flags = SLB_VSID_KERNEL | mmu_psize_defs[mmu_io_psize].sllp; } else {
With preempt enabled we see warnings in do_slb_fault(): BUG: using smp_processor_id() in preemptible [00000000] code: kworker/u33:0/98 futex hash table entries: 4096 (order: 3, 524288 bytes) caller is do_slb_fault+0x204/0x230 CPU: 5 PID: 98 Comm: kworker/u33:0 Not tainted 4.19.0-rc3-gcc-7.3.1-00022-g1936f094e164 #138 Call Trace: dump_stack+0xb4/0x104 (unreliable) check_preemption_disabled+0x148/0x150 do_slb_fault+0x204/0x230 data_access_slb_common+0x138/0x180 This is caused by the get_paca() in slb_allocate_kernel(), which includes a call to debug_smp_processor_id(). slb_allocate_kernel() can only be called from do_slb_fault(), and in that path interrupts are hard disabled and so we can't be preempted, but we can't update the preempt flags (in thread_info) because that could cause an SLB fault. So just use local_paca which is safe and doesn't cause the warning. Fixes: 48e7b7695745 ("powerpc/64s/hash: Convert SLB miss handlers to C") Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> --- arch/powerpc/mm/slb.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)