On Mon, Dec 02, 2013 at 02:45:06AM +0100, Michael Trimarchi wrote: > On Mon, Dec 2, 2013 at 1:24 AM, Anton Vorontsov <anton@xxxxxxxxxx> wrote: > > On Mon, Dec 02, 2013 at 01:02:40AM +0100, Michael Trimarchi wrote: > >> On Sun, Dec 1, 2013 at 11:37 PM, Anton Vorontsov <anton@xxxxxxxxxx> wrote: > >> > On Mon, Nov 25, 2013 at 08:16:34PM +0100, Michael Trimarchi wrote: > >> > ... > >> >> >> So you can read this value without any type of synchronization > >> >> >> with the power_supply_core > >> >> >> and sysfs implementation? > >> > ... > >> >> https://lists.ubuntu.com/archives/kernel-team/2013-January/025206.html > >> >> > >> >> I found and equivalent scenario that I was trying to said > >> > > >> > That's a good question, actually. Even though in Pali's case the notifier > >> > is atomic (so that we are pretty confident that the object won't be > >> > unregistered), there is still a possiblity of a dead lock, for example. So > >> > >> So if the get_property is a sleeping function it will be a deadlock. Right? > > > > All kind of bad things might happen, yes. But before that I would expect a > > bunch of warnings from might_sleep() stuff. > > > > I would recommend to test the patches using preempt/smp kernels + various > > DEBUG_ kernel options set. > > > > Is it more simple to make it not atomic and use a mutex in get_property? I just built a kernel with CONFIG_DEBUG_ATOMIC_SLEEP to test another driver and got the following output for bq2415x: [ 7.667449] Workqueue: events power_supply_changed_work [ 7.673034] [<c0015c28>] (unwind_backtrace+0x0/0xe0) from [<c0011e1c>] (show_stack+0x10/0x14) [ 7.682098] [<c0011e1c>] (show_stack+0x10/0x14) from [<c052cdd0>] (dump_stack+0x78/0xac) [ 7.690704] [<c052cdd0>] (dump_stack+0x78/0xac) from [<c052a044>] (__schedule_bug+0x48/0x60) [ 7.699645] [<c052a044>] (__schedule_bug+0x48/0x60) from [<c053071c>] (__schedule+0x74/0x638) [ 7.708618] [<c053071c>] (__schedule+0x74/0x638) from [<c05301fc>] (schedule_timeout+0x1dc/0x24c) [ 7.718017] [<c05301fc>] (schedule_timeout+0x1dc/0x24c) from [<c05316ec>] (wait_for_common+0x138/0x17c) [ 7.727966] [<c05316ec>] (wait_for_common+0x138/0x17c) from [<c0362a70>] (omap_i2c_xfer+0x340/0x4a0) [ 7.737640] [<c0362a70>] (omap_i2c_xfer+0x340/0x4a0) from [<c035d928>] (__i2c_transfer+0x40/0x74) [ 7.747039] [<c035d928>] (__i2c_transfer+0x40/0x74) from [<c035e22c>] (i2c_transfer+0x6c/0x90) [ 7.756195] [<c035e22c>] (i2c_transfer+0x6c/0x90) from [<c037ad24>] (bq2415x_i2c_write+0x48/0x78) [ 7.765563] [<c037ad24>] (bq2415x_i2c_write+0x48/0x78) from [<c037ae60>] (bq2415x_set_weak_battery_voltage+0x4c/0x50) [ 7.776824] [<c037ae60>] (bq2415x_set_weak_battery_voltage+0x4c/0x50) from [<c037bce8>] (bq2415x_set_mode+0xdc/0x14c) [ 7.788085] [<c037bce8>] (bq2415x_set_mode+0xdc/0x14c) from [<c037bfb8>] (bq2415x_notifier_call+0xa8/0xb4) [ 7.798309] [<c037bfb8>] (bq2415x_notifier_call+0xa8/0xb4) from [<c005f228>] (notifier_call_chain+0x38/0x68) [ 7.808715] [<c005f228>] (notifier_call_chain+0x38/0x68) from [<c005f284>] (__atomic_notifier_call_chain+0x2c/0x3c) [ 7.819732] [<c005f284>] (__atomic_notifier_call_chain+0x2c/0x3c) from [<c005f2a8>] (atomic_notifier_call_chain+0x14/0x18) [ 7.831420] [<c005f2a8>] (atomic_notifier_call_chain+0x14/0x18) from [<c0378078>] (power_supply_changed_work+0x6c/0xb8) [ 7.842864] [<c0378078>] (power_supply_changed_work+0x6c/0xb8) from [<c00556c0>] (process_one_work+0x248/0x440) [ 7.853546] [<c00556c0>] (process_one_work+0x248/0x440) from [<c0055d6c>] (worker_thread+0x208/0x350) [ 7.863372] [<c0055d6c>] (worker_thread+0x208/0x350) from [<c005b0ac>] (kthread+0xc8/0xdc) [ 7.872131] [<c005b0ac>] (kthread+0xc8/0xdc) from [<c000e138>] (ret_from_fork+0x14/0x3c) -- Sebastian
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