Hi On Sun, Jan 19, 2014 at 9:54 PM, Sebastian Reichel <sre@xxxxxxxx> wrote: > 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 I have already give my opinion about this problem Michael -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
