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authorTzung-Bi Shih <tzungbi@google.com>2020-01-17 15:38:12 +0800
committerMark Brown <broonie@kernel.org>2020-01-21 17:14:33 +0000
commit08df0d9a00f7ca07511614dd3b137fadd2de56fc (patch)
tree292519fbbdb910f297408fbf92691ea68d8e473c /fs/binfmt_em86.c
parent250a15cf575a655097151ad887cea02dd0977136 (diff)
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ASoC: max98090: revert "ASoC: max98090: fix lockdep warning"
Commit 2dc98af62c32 ("ASoC: max98090: fix lockdep warning") introduced a helpful-less small lock: shdn_lock. Reverts the commit. Reasons: 1. Lockdep should not be happy by either the original or current code. From lockdep's point of view, there is a lock inversion anyway. Let d = dapm_mutex, c = controls_rwsem, s = shdn_lock, From the reported calling stack: lock acquisition order of snd_soc_register_card() is: d -> c. > snd_ctl_add_replace+0x3c/0x84 > dapm_create_or_share_kcontrol+0x24c/0x2e0 > snd_soc_dapm_new_widgets+0x308/0x594 > snd_soc_bind_card+0x80c/0xad4 > devm_snd_soc_register_card+0x34/0x6c If calling snd_soc_dapm_put_enum_double() in kcontrol's put (e.g. SOC_DAPM_ENUM_EXT), lock acquisition order is: c -> d. Note that, snd_soc_dapm_put_enum_double() acquires d. The possible lock inversion is always there if registering sound card and putting mixer control happen at the same time. In fact, it never happens because the control device don't show up to the userspace until the sound card build success. Commit 2dc98af62c32 ("ASoC: max98090: fix lockdep warning") changes the order to: c -> s -> d. The lock inversion is still there. 2. Commit 62d5ae4cafb7 ("ASoC: max98090: save and restore SHDN when changing sensitive registers SHDN bit") designed to use dapm_mutex to protect SHDN bit. Use a separate lock breaks the protection. DAPM changes SHDN bit automatically when it finds the path. Thus, any code wants to change the SHDN bit, need to acquire the dapm_mutex first. > SND_SOC_DAPM_SUPPLY("SHDN", M98090_REG_DEVICE_SHUTDOWN, > M98090_SHDNN_SHIFT, 0, NULL, 0), Fixes: 2dc98af62c32 ("ASoC: max98090: fix lockdep warning") Signed-off-by: Tzung-Bi Shih <tzungbi@google.com> Link: https://lore.kernel.org/r/20200117073814.82441-2-tzungbi@google.com Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'fs/binfmt_em86.c')
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