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Hi Rafael, I am working on device driver whose some part is user space and some part is kernel space. So the user space part of the driver provides interface to user space applications. 1) Now, Suppose some user space is application is going on which is accessing the user space driver and user space driver scheduled some jobs to kernel space, Now suppose system hibernation start, since it freezes all the user space processes so suppose jobs are not completed yet which are scheduled to kernel space by user space. when the kernel space device driver completes the jobs and gives the notification to user space driver, since user space process is already frozen, so there will be problem if we suspend the driver using suspend and resume. right? 2) The other point I was seeing, when the power management core freezes all the processes before suspending and resuming devices, it will take some time for freezing and after that if some device driver refuses to suspend, then it will again resume the whole processes, so latency time be more. right? 3) Next question is regarding the kernel space threads, when these are frozen during suspend/hibernation? Thanks Raj > Date: Wed, 6 Oct 2010 00:43:30 +0200 > From: "Rafael J. Wysocki" <rjw@xxxxxxx> > Subject: Re: Question about hibernation > To: linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx > Message-ID: <201010060043.30489.rjw@xxxxxxx> > Content-Type: Text/Plain; charset="iso-8859-2" > > On Tuesday, October 05, 2010, Raj Kumar wrote: > > > > Hi Alan, > > > > I have question regarding the hibernation mode in linux. > > > > 1) In normal suspend to ram, is freezing of tasks necessary while suspend to ram in current linux power management core? > > Yes, it is. > > > 2) In hibernation mode, is freezing of tasks done before normal suspend/resumes in order to that hibernation image is in sync? > > That depends on what you mean by normal "suspend/resumes". Generally speaking, > the hibernate code freezes tasks before preallocating image memory. > > > My issue is because it might be possible that there is some part of device driver which is user space and another part is kernel space > > then in suspend to ram and hibernation mode is freezing of all user space part is done before kernel side or it differs while > > suspend to ram and hibernation mode? > > User space is always frozen before suspend and hibernation. > > Thanks, > Rafael > > |
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