ACPI: CPPC: Release PCC data after probe failures

pcc_data_alloc() takes a per-processor reference while parsing the first
PCC register. Every later probe failure currently frees the CPC descriptor
without dropping that reference. Depending on where probe fails, this
leaks an unacquired PCC object, an acquired mailbox channel, or an extra
reference to a shared channel.

Factor the teardown into pcc_data_put() so it handles both acquired and
unacquired state, and invoke it on every failure after allocation.

Allocation, reference updates, channel setup, and teardown of a shared
subspace are also unsynchronized. Concurrent processor probe and removal
can lose a reference update, free a live object, or request and initialize
the same mailbox channel twice. Protect that lifecycle with a mutex and
publish pcc_channel_acquired only after its lock and wait queue have been
initialized.

Do not store the temporary pcc_data_alloc() result in the eventual probe
return value. A successful allocation must not make a later parsing failure
run cleanup and then return success.

A later processor-start step can fail after CPPC probe has published its
descriptor. Reuse that descriptor when processor start is retried instead
of resetting its PCC index and reparsing _CPC. This prevents the live
descriptor from becoming detached from its PCC reference.

The per-CPU PCC subspace index is zero-initialized. If probe returns before
assigning it, a later processor exit can consequently drop the reference
for subspace 0 even though this CPU never acquired one. Initialize the
index to -1 before any probe return and only release it from exit after a
CPC descriptor has been published.

Fixes: 85b1407bf6d2 ("ACPI / CPPC: Make CPPC ACPI driver aware of PCC subspace IDs")
Signed-off-by: Christian Loehle <christian.loehle@arm.com>
Tested-by: Sumit Gupta <sumitg@nvidia.com>
Link: https://patch.msgid.link/20260916162805.1039247-8-christian.loehle@arm.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

0 files changed, 0 insertions, 0 deletions