7:56 a.m.
Hi Tao,
Thank you for the feedback. I will make the adjustment and send
the commit, along with an improved commit message.
Best regards,
Lucas
On Wed, May 6, 2026 at 1:12 AM Tao Liu <ltao(a)redhat.com> wrote:
Hi Lucas,
Thanks for the fix.
On Fri, Apr 24, 2026 at 9:17 AM Lucas Oakley <soakley(a)redhat.com> wrote:
>
> In RHEL 9.4 ppc64le, the stack size was adjusted from 16k to
> 32k. As a result, ppc64_back_trace() can bail prematurely when
> checking if the stack pointer exists in the range of the
> range of the irq stacks, since SIZE(irq_ctx), used in
> ppc64_in_irqstack(), is set to 16k. This patch ensures that
> irq_ctx is updated to 32k if a 32k stack size is used.
>
> Tested against:
> el6 x86_64
> el7 ppc64le s390x x86_64
> el8 aarch64 ppc64le s390x x86_64
> el9 aarch64 ppc64le s390x x86_64
> el10 aarch64 ppc64le s390x x86_64
>
> Without the commit:
>
> crash> bt -c 3
> PID: 17524 TASK: c0000000b2c0e400 CPU: 3 COMMAND: "xyz"
> cannot find the stack info.
>
> With the commit:
>
> crash> bt -c 3
> PID: 17524 TASK: c0000000b2c0e400 CPU: 3 COMMAND: "xyz"
> #0 [c000001dff7d7c10] smp_call_function_single_async at
c00000000028dd38
> #1 [c000001dff7d7d30] _raw_spin_lock_irqsave at c000000001023f1c
> #2 [c000001dff7d7d60] ibmvscsi_handle_crq at c0080000044635ec
[ibmvscsi]
> #3 [c000001dff7d7de0] ibmvscsi_task at c008000004463804 [ibmvscsi]
> #4 [c000001dff7d7e30] tasklet_action_common.constprop.0 at
c0000000001624cc
> #5 [c000001dff7d7e90] __do_softirq at c0000000010244cc
> #6 [c000001dff7d7f90] do_softirq_own_stack at c000000000016480
> #7 [c000000140d67700] __irq_exit_rcu at c0000000001613b8
> #8 [c000000140d67730] irq_exit at c000000000162170
> #9 [c000000140d67750] do_IRQ at c000000000015fa4
> #10 [c000000140d67780] hardware_interrupt_common_virt at
c000000000009080
> Hardware Interrupt [500] exception frame:
> R0: c000000001023de0 R1: c000000140d67a90 R2:
c000000002c02500
> R3: c00800000b30269c R4: 0000000000000001 R5:
0000000000000001
> R6: ffffffffffffffff R7: 0000000000000000 R8:
0000000000000000
> R9: fffffffffffe0000 R10: 0000000000000002 R11:
0000000048422824
> R12: c000000001023d70 R13: c000001dffffd480 R14:
00007ffd6ef6d238
> R15: 0000000000000028 R16: c000001dfc1e2280 R17:
c000001dfc1e2280
> R18: 00000000ab97fa48 R19: 0000000000000000 R20:
0000000000000001
> R21: 0000001df9ff0000 R22: 0000000000000028 R23:
c0000000021f2280
> R24: 0000000000000000 R25: c0000000021f2280 R26:
c0000000021f2380
> R27: 0000000000000000 R28: c00800000b30269c R29:
0000000000000000
> R30: c000000002c47190 R31: 000000000020000b
> NIP: c0000000000aea14 MSR: 800000000280b033 OR3:
c0000000000ae944
> CTR: c000000001023d70 LR: c000000001023de0 XER:
0000000020040001
> CCR: 0000000088422824 MQ: 0000000000000000 DAR:
0000000000000001
> DSISR: c0080000073b1e94 Syscall Result: 0000000000000000
> [NIP : queued_spin_lock_slowpath+1204]
> [LR : _raw_spin_lock+112]
> #11 [c000000140d67a90] queued_spin_lock_slowpath at c0000000000aea14
> #12 [c000000140d67bb0] _raw_spin_lock at c000000001023de0
(unreliable)
> #13 [c000000140d67bd0] dm_blk_close at c00800000b2c6850 [dm_mod]
> #14 [c000000140d67c00] blkdev_put_whole at c0000000007d2738
> #15 [c000000140d67c30] bdev_release at c0000000007d3a38
> #16 [c000000140d67c90] blkdev_release at c0000000007d4224
> #17 [c000000140d67cb0] __fput at c0000000005d2e98
> #18 [c000000140d67d00] task_work_run at c00000000018fb14
> #19 [c000000140d67d50] do_notify_resume at c000000000020bd4
> #20 [c000000140d67d80] interrupt_exit_user_prepare_main at
c00000000002ed98
> #21 [c000000140d67de0] syscall_exit_prepare at c00000000002f240
> #22 [c000000140d67e10] system_call_vectored_common at
c00000000000bff4
>
> Signed-off-by: Lucas Oakley <soakley(a)redhat.com>
> ---
> task.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/task.c b/task.c
> index ec04b55..a398a8d 100644
> --- a/task.c
> +++ b/task.c
> @@ -739,6 +739,18 @@ irqstacks_init(void)
> if (!(tt->softirq_tasks = (ulong *)calloc(NR_CPUS,
sizeof(ulong))))
> error(FATAL, "cannot malloc softirq_tasks space.");
>
> + /*
> + * RHEL 9.4.z adjusted the stack size from 16k to 32k for
> + * ppc64le only. We need to ensure that SIZE(irq_ctx) is
> + * correctly set so the unwinder doesn't prematurely bail
> + * when switching between the kernel stack and irq stacks.
> + * The stack size is updated in task_init(), which calls
> + * this routine, irqstacks_init() after checking for the
> + * existence of irq_ctx.
> + */
> + if ((SIZE(irq_ctx) != -1) && (STACKSIZE() > SIZE(irq_ctx)))
> + ASSIGN_SIZE(irq_ctx) = STACKSIZE();
> +
I think the (SIZE(irq_ctx) != -1) check is not needed. Because when
entering the function, VALID_STRUCT(irq_ctx) already ensure
size_table.irq_ctx >= 0, so (SIZE(irq_ctx) != -1) is always true. I
have no other concerns for the patch.
Thanks,
Tao Liu
> thread_info_buf = GETBUF(SIZE(irq_ctx));
>
> if ((hard_sp = per_cpu_symbol_search("per_cpu__hardirq_ctx")) ||
> --
> 2.52.0
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