| Subject | Re: [PATCH 4.4 40/57] tpm: Provide strong locking for device removal | From | Ben Hutchings <> | Date | Tue, 25 Jul 2017 23:56:01 +0100 |
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On Wed, 2017-07-19 at 13:12 +0200, Greg Kroah-Hartman wrote: > 4.4-stable review patch. If anyone has any objections, please let me know. > > ------------------ > > From: Jason Gunthorpe <jgunthorpe@obsidianresearch.com> > > commit 4e26195f240d73150e8308ae42874702e3df8d2c upstream. > > Add a read/write semaphore around the ops function pointers so > ops can be set to null when the driver un-registers. [...] > @@ -49,10 +99,10 @@ struct tpm_chip *tpm_chip_find_get(int c > if (chip_num != TPM_ANY_NUM && chip_num != pos->dev_num) > continue; > > - if (try_module_get(pos->dev.parent->driver->owner)) { > + /* rcu prevents chip from being free'd */ > + if (!tpm_try_get_ops(pos)) [...]
But an RCU read-side critical section is an atomic context, and semaphore operations can block! Fixed upstream by:
commit 15516788e581eb32ec1c50e5f00aba3faf95d817 Author: Stefan Berger <stefanb@linux.vnet.ibm.com> Date: Mon Feb 29 08:53:02 2016 -0500
tpm: Replace device number bitmap with IDR
Ben.
-- Ben Hutchings Software Developer, Codethink Ltd.
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