> -----Original Message----- > From: Russell King - ARM Linux [mailto:li...@arm.linux.org.uk] > Sent: Thursday, January 08, 2015 7:42 PM > To: Wang, Yalin > Cc: 'ch...@printf.net'; 'ulf.hans...@linaro.org'; 'tim.kry...@gmail.com'; > 'tgih....@samsung.com'; 'johan.rudh...@axis.com'; 'linux- > m...@vger.kernel.org'; 'linux-kernel@vger.kernel.org'; 'linux-arm- > ker...@lists.infradead.org' > Subject: Re: [RFC] mmc:change mmc_init workqueue into a freezable workqueue > > On Thu, Jan 08, 2015 at 06:06:32PM +0800, Wang, Yalin wrote: > > This patch fix the mmc driver suspend/resume conflict problems, mmc > > workqueue will queue mmc_rescan(), and it will call some > > pm_runtime_* functions, this will conflict with suspend path > > sometimes, and will result in some strange behavior: > > > > Suspend path: > > -000 |context_switch(inline) > > -000 |__schedule() > > -001 |schedule_preempt_disabled() > > -002 |spin_lock(inline) > > -002 |__mutex_lock_common(inline) > > -002 |__mutex_lock_slowpath(lock_count = 0xEDCD0F48) > > -003 |__mutex_fastpath_lock(inline) > > -003 |mutex_lock(lock = 0xEDCD0F48) > > -004 |sdhci_do_set_ios(host = 0xEDCD0CC0, ios = 0xEDCD0A70) > > -005 |sdhci_set_ios(?, ios = 0xEDCD0A70) > > -006 |mmc_set_ios(host = 0xEDCD0800) > > -007 |mmc_delay(inline) > > -007 |mmc_power_off(host = 0xEDCD0800) > > -008 |mmc_suspend_host(inline) > > -008 |mmc_suspend_host(host = 0xEDCD0800) > > -009 |mmc_host_suspend(dev = 0xEDCD0808) > > -010 |dpm_run_callback(cb = 0xC0627A88, dev = 0xEDCD0808, state = > (event = 2), info = 0xC0B6EF9B) > > -011 |__device_suspend(dev = 0xEDCD0808, state = (event = 2), ?) > > -012 |device_suspend(inline) > > Suspend can't complete until device_suspend() returns. Hence, > mmc_power_off() must finish. > > > mmc_rescan() resume path: > > -000 |context_switch(inline) > > -000 |__schedule() > > -001 |do_undefinstr(regs = 0xD12242F0) > > -002 |__und_svc(asm) > > --> |exception > > I assume this is what you mean by "strange behaviour" ? If so, please give > the full oops. Have you fully diagnosed the failure? > > > most mmc power callback function don't check this special case, and > > will cause problems, make sure the workqueue is stopped during suspend > > is more safe. > > I think there's a bad side effect of this: if you have swap on a SD card, > and you ask the system to hibernate, you don't want this thread to freeze. > > What you do need to do is to ensure that new requests can't be processed > while the host is suspended. > > A hibernate works (approximately) as: > > - freeze all tasks > - push as much out to swap as possible > - suspend devices > - create system snapshot > - resume devices > - write system snapshot to swap > - power down > > If the MMC thread is frozen, and you have swap on SD, then it can't write > the image to swap. > I see your concerns, thanks for your comment. I will think about some other solutions for this problems.
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