RE: [PATCH 09/11] scsi: ufs: Fix a kernel crash during shutdown

Avri Altman
2021-11-11T07:49:08Z

> Fix the following kernel crash:
>
> Unable to handle kernel paging request at virtual address ffffffc91e735000 Call
> trace:
> __queue_work+0x26c/0x624
> queue_work_on+0x6c/0xf0
> ufshcd_hold+0x12c/0x210
> __ufshcd_wl_suspend+0xc0/0x400
> ufshcd_wl_shutdown+0xb8/0xcc
> device_shutdown+0x184/0x224
> kernel_restart+0x4c/0x124
> __arm64_sys_reboot+0x194/0x264
> el0_svc_common+0xc8/0x1d4
> do_el0_svc+0x30/0x8c
> el0_svc+0x20/0x30
> el0_sync_handler+0x84/0xe4
> el0_sync+0x1bc/0x1c0
>
> Fix this crash by ungating the clock before destroying the work queue on which
> clock gating work is queued.
>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
> drivers/scsi/ufs/ufshcd.c | 15 ++++++++++-----
> 1 file changed, 10 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c index
> 1e15ed1f639f..13848e93cda8 100644
> --- a/drivers/scsi/ufs/ufshcd.c
> +++ b/drivers/scsi/ufs/ufshcd.c
> @@ -1666,7 +1666,8 @@ int ufshcd_hold(struct ufs_hba *hba, bool async)
> bool flush_result;
> unsigned long flags;
>
> - if (!ufshcd_is_clkgating_allowed(hba))
> + if (!ufshcd_is_clkgating_allowed(hba) ||
> + !hba->clk_gating.is_initialized)
> goto out;
> spin_lock_irqsave(hba->host->host_lock, flags);
> hba->clk_gating.active_reqs++;
> @@ -1826,7 +1827,7 @@ static void __ufshcd_release(struct ufs_hba *hba)
>
> if (hba->clk_gating.active_reqs || hba->clk_gating.is_suspended ||
> hba->ufshcd_state != UFSHCD_STATE_OPERATIONAL ||
> - hba->outstanding_tasks ||
> + hba->outstanding_tasks || !hba->clk_gating.is_initialized ||
> hba->active_uic_cmd || hba->uic_async_done ||
> hba->clk_gating.state == CLKS_OFF)
> return;
> @@ -1961,11 +1962,15 @@ static void ufshcd_exit_clk_gating(struct ufs_hba
> *hba) {
> if (!hba->clk_gating.is_initialized)
> return;
> +
> ufshcd_remove_clk_gating_sysfs(hba);
> - cancel_work_sync(&hba->clk_gating.ungate_work);
> - cancel_delayed_work_sync(&hba->clk_gating.gate_work);
> - destroy_workqueue(hba->clk_gating.clk_gating_workq);
> +
> + /* Ungate the clock if necessary. */
> + ufshcd_hold(hba, false);
> hba->clk_gating.is_initialized = false;
> + ufshcd_release(hba);
Not sure that the symmetry in calling ufshcd_release() is meaningful here?
You don't really want to queue a new gate work, this is why you added !.is_initialized to release(),
Or did I get it wrong?

Thanks,
Avri
> +
> + destroy_workqueue(hba->clk_gating.clk_gating_workq);
> }
>
> /* Must be called with host lock acquired */