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tpm: Provide strong locking for device removal

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Add a read/write semaphore around the ops function pointers so
ops can be set to null when the driver un-registers.

Previously the tpm core expected module locking to be enough to
ensure that tpm_unregister could not be called during certain times,
however that hasn't been sufficient for a long time.

Introduce a read/write semaphore around 'ops' so the core can set
it to null when unregistering. This provides a strong fence around
the driver callbacks, guaranteeing to the driver that no callbacks
are running or will run again.

For now the ops_lock is placed very high in the call stack, it could
be pushed down and made more granular in future if necessary.

Signed-off-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Reviewed-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
This commit is contained in:
Jason Gunthorpe
2016-02-12 20:29:53 -07:00
committed by Jarkko Sakkinen
parent 3635e2ec7c
commit 4e26195f24
5 changed files with 100 additions and 21 deletions
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5
drivers/char/tpm/tpm-sysfs.c
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@@ -295,5 +295,10 @@ int tpm_sysfs_add_device(struct tpm_chip *chip)
void tpm_sysfs_del_device(struct tpm_chip *chip)
{
/* The sysfs routines rely on an implicit tpm_try_get_ops, this
* function is called before ops is null'd and the sysfs core
* synchronizes this removal so that no callbacks are running or can
* run again
*/
sysfs_remove_group(&chip->dev.parent->kobj, &tpm_dev_group);
}