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Date: Sat, 02 Jan 2021 21:10:52 +0800 From: Can Guo <cang@...eaurora.org> To: Bart Van Assche <bvanassche@....org> Cc: asutoshd@...eaurora.org, nguyenb@...eaurora.org, hongwus@...eaurora.org, ziqichen@...eaurora.org, rnayak@...eaurora.org, linux-scsi@...r.kernel.org, kernel-team@...roid.com, saravanak@...gle.com, salyzyn@...gle.com, Alim Akhtar <alim.akhtar@...sung.com>, Avri Altman <avri.altman@....com>, "James E.J. Bottomley" <jejb@...ux.ibm.com>, "Martin K. Petersen" <martin.petersen@...cle.com>, Stanley Chu <stanley.chu@...iatek.com>, Bean Huo <beanhuo@...ron.com>, open list <linux-kernel@...r.kernel.org> Subject: Re: [PATCH v2 1/2] scsi: ufs: Fix a possible NULL pointer issue On 2021-01-02 20:29, Can Guo wrote: > On 2021-01-02 00:05, Bart Van Assche wrote: >> On 12/31/20 9:44 PM, Can Guo wrote: >>> During system resume/suspend, hba could be NULL. In this case, do not >>> touch >>> eh_sem. >>> >>> Fixes: 88a92d6ae4fe ("scsi: ufs: Serialize eh_work with system PM >>> events and async scan") >>> >>> Signed-off-by: Can Guo <cang@...eaurora.org> >>> --- >>> drivers/scsi/ufs/ufshcd.c | 9 +++++---- >>> 1 file changed, 5 insertions(+), 4 deletions(-) >>> >>> diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c >>> index e221add..34e2541 100644 >>> --- a/drivers/scsi/ufs/ufshcd.c >>> +++ b/drivers/scsi/ufs/ufshcd.c >>> @@ -8896,8 +8896,11 @@ int ufshcd_system_suspend(struct ufs_hba *hba) >>> int ret = 0; >>> ktime_t start = ktime_get(); >>> >>> + if (!hba) >>> + return 0; >>> + >>> down(&hba->eh_sem); >>> - if (!hba || !hba->is_powered) >>> + if (!hba->is_powered) >>> return 0; >>> >>> if ((ufs_get_pm_lvl_to_dev_pwr_mode(hba->spm_lvl) == >>> @@ -8945,10 +8948,8 @@ int ufshcd_system_resume(struct ufs_hba *hba) >>> int ret = 0; >>> ktime_t start = ktime_get(); >>> >>> - if (!hba) { >>> - up(&hba->eh_sem); >>> + if (!hba) >>> return -EINVAL; >>> - } >>> >>> if (!hba->is_powered || pm_runtime_suspended(hba->dev)) >>> /* >> >> Hi Can, >> >> How can ufshcd_system_suspend() or ufshcd_system_resume() be called >> with a >> NULL argument? In ufshcd_pci_probe() I see that pci_set_drvdata() is >> called >> before pm_runtime_allow(). ufshcd_pci_remove() calls >> pm_runtime_forbid(). >> >> Thanks, >> >> Bart. > > Hi Bart, > > You are right about ufshcd_RUNTIME_suspend/resume() - > platform_set_drvdata() > is called before pm_runtime_enable(), so runtime suspend/resume cannot > happen > before pm_runtime_enable() is called. We can remove the sanity checks > of > !hba there, they are outdated. Add more history here - before Stanley's change (see below), platform_set_drvdata() is called AFTER pm_runtime_enable(), which was why we needed sanity checks of !hba. But now the sanity checks are unnecessary in ufshcd_RUNTIME_suspend/resume(), so feel free to remove them. But still, things are a bit different for ufshcd_SYSTEM_suspend/resume(), we need the sanity checks of !hba there if my understanding is correct. commit 24e2e7a19f7e4b83d0d5189040d997bce3596473 Author: Stanley Chu <stanley.chu@...iatek.com> Date: Wed Jun 12 23:19:05 2019 +0800 scsi: ufs: Avoid runtime suspend possibly being blocked forever Thanks, Can Guo. > > But for ufshcd_SYSTEM_suspend/resume() callbacks (not runtime ones), my > understanding is that system suspend/resume may happen after probe > (vendor > driver probe calls ufshcd_pltfrm_init()) starts but before > platform_set_drvdata() > is called, in this case hba is NULL. > > int ufshcd_pltfrm_init(struct platform_device *pdev, > const struct ufs_hba_variant_ops *vops) > { > ... > platform_set_drvdata(pdev, hba); > > pm_runtime_set_active(&pdev->dev); > pm_runtime_enable(&pdev->dev); > } > > Thanks, > > Can Guo.
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