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Message-ID: <CAGhQ9VzJtx3MJF1wdJd8hv7Hp4T0YJK=vNbJWGj_W7X+mLy-xQ@mail.gmail.com> Date: Thu, 27 Sep 2012 19:22:38 +0200 From: Joachim Eastwood <manabian@...il.com> To: Russell King - ARM Linux <linux@....linux.org.uk> Cc: Ming Lei <tom.leiming@...il.com>, Arnd Bergmann <arnd@...db.de>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Mark Brown <broonie@...nsource.wolfsonmicro.com>, linux-kernel@...r.kernel.org, Grant Likely <grant.likely@...retlab.ca>, linux-arm-kernel@...ts.infradead.org Subject: Re: [BUG] Deferred probing in driver model is racy, resulting in lost probes Hi, On Thu, Sep 27, 2012 at 4:03 PM, Russell King - ARM Linux <linux@....linux.org.uk> wrote: > On Thu, Sep 27, 2012 at 02:58:09PM +0100, Russell King - ARM Linux wrote: >> On Thu, Sep 27, 2012 at 07:47:46AM +0800, Ming Lei wrote: >> > On Thu, Sep 27, 2012 at 4:23 AM, Russell King - ARM Linux >> > <linux@....linux.org.uk> wrote: >> > > To be honest, I've not bothered to test the above patch, and now when I >> > > look at it, I notice it's broken - in that on error it will corrupt the >> > > driver list. Take a look at the error path. >> > > >> > > priv is drv->p. We add priv->knode_bus to the driver list. If >> > > driver_attach() returns an error, then we go to out_unregister, which >> > >> > In fact, driver_attach() always returns zero, so it does __not__ affect >> > your test. >> >> It may not affect my test, but the fact is, that patch lays down the >> foundations for bugs to be introduced. Now, while I can test it (and >> have done) I don't think it's suitable for mainline because of _that_. >> >> If driver_attach() always returns zero, there's no point in it returning >> a value - it might as well return void and stop leading people to >> believe that it might return an error. So I suggest this alternative >> patch instead, which gets rid of what is effectively dead code, and >> probably a few warnings about not checking the return value from a >> __must_check function (see usb-serial.c). >> >> With this patch, no one is lead into a false sense of security that, >> after your patch, if driver_attach() ever returns an error, proper >> cleanup will happen - it's blatently obvious to anyone modifying it >> that if they do want it to return an error, they have to audit all the >> users of it, which IMHO is a good thing. > > Sorry, old version of that patch. Here's the right one. <snip patch> I am also having problems with ASoC modules and deferred probing. This patch seems to improve the a lot situation, though. Now it work most of the time, but occasionally I get the warning below. Not sure if this is directly related to the issue Russell have been seeing. Guess it can be races in the Atmel ASoC drivers as well(?). [ 12.230000] mpa1600-audio mpa1600-audio.0: CODEC wm8776.0-001b not registered [ 12.390000] mpa1600-audio mpa1600-audio.0: snd_soc_register_card() failed: -517 [ 12.390000] platform mpa1600-audio.0: Driver mpa1600-audio requests probe deferral [ 12.720000] ------------[ cut here ]------------ [ 12.720000] WARNING: at fs/sysfs/dir.c:536 sysfs_add_one+0x7c/0xa0() [ 12.740000] mpa1600-audio mpa1600-audio.1: CODEC wm8776.0-001a not registered [ 12.910000] mpa1600-audio mpa1600-audio.1: snd_soc_register_card() failed: -517 [ 13.140000] sysfs: cannot create duplicate filename '/devices/platform/ssc.0/atmel-ssc-dai.0' [ 13.140000] Modules linked in: snd_soc_mpa1600_wm8776(+) snd_soc_atmel_ssc_dai snd_soc_core pcmcia regmap_i2c snd_pcm snd_page_alloc ad525x_dpot_i2c snd_timer ad525x_dpot ohci_hcd leds_pca9532 snd usbcore soundcore gpio_keys rege [ 13.630000] Backtrace: [ 13.630000] [<c000c46c>] (dump_backtrace+0x0/0x10c) from [<c021ac48>] (dump_stack+0x18/0x1c) [ 13.980000] r7:c3839ca8 r6:c00d0cf0 r5:c0278f34 r4:00000218 [ 13.990000] [<c021ac30>] (dump_stack+0x0/0x1c) from [<c0015ad0>] (warn_slowpath_common+0x54/0x6c) [ 14.240000] [<c0015a7c>] (warn_slowpath_common+0x0/0x6c) from [<c0015b8c>] (warn_slowpath_fmt+0x38/0x40) [ 14.470000] r8:c2d41110 r7:ffffffef r6:c3839ce8 r5:c3a47780 r4:c2c58000 [ 14.480000] [<c0015b54>] (warn_slowpath_fmt+0x0/0x40) from [<c00d0cf0>] (sysfs_add_one+0x7c/0xa0) [ 14.660000] r3:c2c58000 r2:c0278f64 [ 14.660000] [<c00d0c74>] (sysfs_add_one+0x0/0xa0) from [<c00d1898>] (create_dir+0x6c/0xc0) [ 14.790000] r7:00000000 r6:00000000 r5:c3a47780 r4:c3839ce8 [ 14.790000] [<c00d182c>] (create_dir+0x0/0xc0) from [<c00d19c4>] (sysfs_create_dir+0xd8/0xf0) [ 14.850000] [<c00d18ec>] (sysfs_create_dir+0x0/0xf0) from [<c01252f8>] (kobject_add_internal+0xe4/0x1e0) [ 14.870000] r7:c2d41b00 r6:c02cc2e0 r5:00000000 r4:c2d41110 [ 14.880000] [<c0125214>] (kobject_add_internal+0x0/0x1e0) from [<c0125644>] (kobject_add_varg+0x44/0x54) [ 14.890000] [<c0125600>] (kobject_add_varg+0x0/0x54) from [<c01256dc>] (kobject_add+0x4c/0x58) [ 14.900000] r6:00000000 r5:c2d41108 r4:c2d41100 [ 14.910000] [<c0125690>] (kobject_add+0x0/0x58) from [<c015220c>] (device_add+0xe4/0x5d0) [ 14.920000] r3:c3839db4 r2:00000000 [ 14.920000] [<c0152128>] (device_add+0x0/0x5d0) from [<c01561a8>] (platform_device_add+0x10c/0x164) [ 14.930000] [<c015609c>] (platform_device_add+0x0/0x164) from [<bf11a9f4>] (atmel_ssc_set_audio+0xac/0xdc [snd_soc_atmel_ssc_dai]) [ 14.940000] r7:c2d41b00 r6:00000000 r5:c2d41100 r4:c02ccf90 [ 14.950000] [<bf11a948>] (atmel_ssc_set_audio+0x0/0xdc [snd_soc_atmel_ssc_dai]) from [<bf11f038>] (mpa1600_audio_probe+0x38/0x88 [snd_soc_mpa1600_wm8776]) [ 14.960000] r7:bf11f464 r6:c02ccf98 r5:bf11f4a0 r4:c02ccf90 [ 14.960000] [<bf11f000>] (mpa1600_audio_probe+0x0/0x88 [snd_soc_mpa1600_wm8776]) from [<c0155b6c>] (platform_drv_probe+0x20/0x24) [ 14.990000] r6:c02ccf98 r5:c02ccf98 r4:bf11f464 [ 14.990000] [<c0155b4c>] (platform_drv_probe+0x0/0x24) from [<c0154680>] (driver_probe_device+0xb8/0x20c) [ 15.000000] [<c01545c8>] (driver_probe_device+0x0/0x20c) from [<c01548a4>] (__device_attach+0x48/0x4c) [ 15.010000] r7:c3839ea8 r6:c02ccf98 r5:c02ccf98 r4:bf11f464 [ 15.020000] [<c015485c>] (__device_attach+0x0/0x4c) from [<c0152dc0>] (bus_for_each_drv+0x5c/0x9c) [ 15.030000] r5:c015485c r4:00000000 [ 15.030000] [<c0152d64>] (bus_for_each_drv+0x0/0x9c) from [<c015493c>] (device_attach+0x6c/0x8c) [ 15.040000] r7:00000089 r6:c02ccfcc r5:c02d7518 r4:c02ccf98 [ 15.050000] [<c01548d0>] (device_attach+0x0/0x8c) from [<c0153988>] (bus_probe_device+0x34/0xa4) [ 15.060000] r6:c02ccf98 r5:c02d7518 r4:c02ccf98 [ 15.060000] [<c0153954>] (bus_probe_device+0x0/0xa4) from [<c0154240>] (deferred_probe_work_func+0x60/0x94) [ 15.070000] r6:c02e3750 r5:c02d7400 r4:c02ccf98 [ 15.080000] [<c01541e0>] (deferred_probe_work_func+0x0/0x94) from [<c002c338>] (process_one_work+0x310/0x4a0) [ 15.090000] r5:c3804500 r4:c02d7408 [ 15.100000] [<c002c028>] (process_one_work+0x0/0x4a0) from [<c002cbc8>] (worker_thread+0x3b8/0x5e0) [ 15.110000] [<c002c810>] (worker_thread+0x0/0x5e0) from [<c00336e4>] (kthread+0x8c/0x98) [ 15.110000] [<c0033658>] (kthread+0x0/0x98) from [<c001b4d4>] (do_exit+0x0/0x720) [ 15.120000] r7:00000013 r6:c001b4d4 r5:c0033658 r4:c3827ecc [ 15.130000] ---[ end trace d7472237284e57c2 ]--- [ 15.130000] platform mpa1600-audio.1: Driver mpa1600-audio requests probe deferral [ 15.150000] ------------[ cut here ]------------ [ 15.150000] WARNING: at lib/kobject.c:196 kobject_add_internal+0x17c/0x1e0() [ 15.250000] kobject_add_internal failed for atmel-ssc-dai.0 with -EEXIST, don't try to register things with the same name in the same directory. [ 15.390000] Modules linked in: snd_soc_mpa1600_wm8776 snd_soc_atmel_ssc_dai snd_soc_core pcmcia regmap_i2c snd_pcm snd_page_alloc ad525x_dpot_i2c snd_timer ad525x_dpot ohci_hcd leds_pca9532 snd usbcore soundcore gpio_keys regmape [ 15.470000] Backtrace: [ 15.470000] [<c000c46c>] (dump_backtrace+0x0/0x10c) from [<c021ac48>] (dump_stack+0x18/0x1c) [ 15.520000] r7:c3839d28 r6:c0125390 r5:c027f187 r4:000000c4 [ 15.520000] [<c021ac30>] (dump_stack+0x0/0x1c) from [<c0015ad0>] (warn_slowpath_common+0x54/0x6c) [ 15.620000] [<c0015a7c>] (warn_slowpath_common+0x0/0x6c) from [<c0015b8c>] (warn_slowpath_fmt+0x38/0x40) [ 15.640000] r8:ffffffef r7:c2d41b00 r6:c02cc2e0 r5:ffffffef r4:c2d41110 [ 15.650000] [<c0015b54>] (warn_slowpath_fmt+0x0/0x40) from [<c0125390>] (kobject_add_internal+0x17c/0x1e0) [ 15.670000] r3:c02247bc r2:c027f21f [ 15.680000] [<c0125214>] (kobject_add_internal+0x0/0x1e0) from [<c0125644>] (kobject_add_varg+0x44/0x54) [ 15.700000] [<c0125600>] (kobject_add_varg+0x0/0x54) from [<c01256dc>] (kobject_add+0x4c/0x58) [ 15.720000] r6:00000000 r5:c2d41108 r4:c2d41100 [ 15.720000] [<c0125690>] (kobject_add+0x0/0x58) from [<c015220c>] (device_add+0xe4/0x5d0) [ 15.740000] r3:c3839db4 r2:00000000 [ 15.760000] [<c0152128>] (device_add+0x0/0x5d0) from [<c01561a8>] (platform_device_add+0x10c/0x164) [ 15.760000] [<c015609c>] (platform_device_add+0x0/0x164) from [<bf11a9f4>] (atmel_ssc_set_audio+0xac/0xdc [snd_soc_atmel_ssc_dai]) [ 15.790000] r7:c2d41b00 r6:00000000 r5:c2d41100 r4:c02ccf90 [ 15.810000] [<bf11a948>] (atmel_ssc_set_audio+0x0/0xdc [snd_soc_atmel_ssc_dai]) from [<bf11f038>] (mpa1600_audio_probe+0x38/0x88 [snd_soc_mpa1600_wm8776]) [ 15.840000] r7:bf11f464 r6:c02ccf98 r5:bf11f4a0 r4:c02ccf90 [ 15.840000] [<bf11f000>] (mpa1600_audio_probe+0x0/0x88 [snd_soc_mpa1600_wm8776]) from [<c0155b6c>] (platform_drv_probe+0x20/0x24) [ 15.860000] r6:c02ccf98 r5:c02ccf98 r4:bf11f464 [ 15.880000] [<c0155b4c>] (platform_drv_probe+0x0/0x24) from [<c0154680>] (driver_probe_device+0xb8/0x20c) [ 15.900000] [<c01545c8>] (driver_probe_device+0x0/0x20c) from [<c01548a4>] (__device_attach+0x48/0x4c) [ 15.910000] r7:c3839ea8 r6:c02ccf98 r5:c02ccf98 r4:bf11f464 [ 15.920000] [<c015485c>] (__device_attach+0x0/0x4c) from [<c0152dc0>] (bus_for_each_drv+0x5c/0x9c) [ 15.940000] r5:c015485c r4:00000000 [ 15.950000] [<c0152d64>] (bus_for_each_drv+0x0/0x9c) from [<c015493c>] (device_attach+0x6c/0x8c) [ 15.960000] r7:00000089 r6:c02ccfcc r5:c02d7518 r4:c02ccf98 [ 15.970000] [<c01548d0>] (device_attach+0x0/0x8c) from [<c0153988>] (bus_probe_device+0x34/0xa4) [ 16.000000] r6:c02ccf98 r5:c02d7518 r4:c02ccf98 [ 16.030000] [<c0153954>] (bus_probe_device+0x0/0xa4) from [<c0154240>] (deferred_probe_work_func+0x60/0x94) [ 16.050000] r6:c02e3750 r5:c02d7400 r4:c02ccf98 [ 16.070000] [<c01541e0>] (deferred_probe_work_func+0x0/0x94) from [<c002c338>] (process_one_work+0x310/0x4a0) [ 16.100000] r5:c3804500 r4:c02d7408 [ 16.100000] [<c002c028>] (process_one_work+0x0/0x4a0) from [<c002cbc8>] (worker_thread+0x3b8/0x5e0) [ 16.120000] [<c002c810>] (worker_thread+0x0/0x5e0) from [<c00336e4>] (kthread+0x8c/0x98) [ 16.140000] [<c0033658>] (kthread+0x0/0x98) from [<c001b4d4>] (do_exit+0x0/0x720) [ 16.150000] r7:00000013 r6:c001b4d4 r5:c0033658 r4:c3827ecc [ 16.160000] ---[ end trace d7472237284e57c3 ]--- [ 16.160000] mpa1600-audio mpa1600-audio.0: Failed to set SSC for audio: -17 [ 16.180000] mpa1600-audio: probe of mpa1600-audio.0 failed with error -17 regards Joachim Eastwood -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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