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mailbox: pcc: Serialize channel updates with shared memory teardown

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mbox_free_channel() makes a PCC channel available before the subsequent
shared-memory unmap. Without serialization, a concurrent request can bind a
new client and replace the mapping, which the old release then unmaps.

Serialize PCC channel acquisition and release. Keep the channel unavailable
until the old shared-memory mapping has been removed.

Suggested-by: Sudeep Holla <sudeep.holla@kernel.org>
Signed-off-by: Christian Loehle <christian.loehle@arm.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>
This commit is contained in:
Christian Loehle 2026-09-03 12:13:28 +01:00 committed by Jassi Brar
parent 4ac21f3fac
commit c5064ac266
1 changed files with 6 additions and 0 deletions
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6
drivers/mailbox/pcc.c
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@ -53,6 +53,7 @@
#include <linux/interrupt.h>
#include <linux/list.h>
#include <linux/log2.h>
#include <linux/mutex.h>
#include <linux/platform_device.h>
#include <linux/mailbox_controller.h>
#include <linux/mailbox_client.h>
@ -113,6 +114,7 @@ struct pcc_chan_info {
#define to_pcc_chan_info(c) container_of(c, struct pcc_chan_info, chan)
static struct pcc_chan_info *chan_info;
static int pcc_chan_count;
static DEFINE_MUTEX(pcc_chan_mutex);
/*
* PCC can be used with perf critical drivers such as CPPC
@ -392,6 +394,8 @@ pcc_mbox_request_channel(struct mbox_client *cl, int subspace_id)
if (subspace_id < 0 || subspace_id >= pcc_chan_count)
return ERR_PTR(-ENOENT);
guard(mutex)(&pcc_chan_mutex);
pchan = chan_info + subspace_id;
chan = pchan->chan.mchan;
if (IS_ERR(chan) || chan->cl) {
@ -434,6 +438,8 @@ void pcc_mbox_free_channel(struct pcc_mbox_chan *pchan)
struct pcc_chan_info *pchan_info;
struct pcc_mbox_chan *pcc_mbox_chan;
guard(mutex)(&pcc_chan_mutex);
if (!chan || !chan->cl)
return;
pchan_info = chan->con_priv;