[PATCH v45 7/7] wrap pchan->chan_in_use in READ/WRITE_ONCE
From: Adam Young <hidden>
Date: 2026-07-21 17:53:32
Also in:
lkml
Subsystem:
acpi pcc(platform communication channel) mailbox driver, mailbox api, the rest · Maintainers:
Sudeep Holla, Jassi Brar, Linus Torvalds
read/write happening from both userspace and Hard IRQ context chan_in_use is used a flag to sychronize access. Volitile semantics ensure we don't have a reordering that accidentally provide dual access. Signed-off-by: Adam Young <redacted> --- drivers/mailbox/pcc.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
index 2ce2afd255f0..dbfe8dd92ddd 100644
--- a/drivers/mailbox/pcc.c
+++ b/drivers/mailbox/pcc.c@@ -325,7 +325,7 @@ static irqreturn_t pcc_mbox_irq(int irq, void *p) return IRQ_NONE; if (pchan->type == ACPI_PCCT_TYPE_EXT_PCC_MASTER_SUBSPACE && - !pchan->chan_in_use) + !READ_ONCE(pchan->chan_in_use)) return IRQ_NONE; if (!pcc_mbox_cmd_complete_check(pchan))
@@ -339,7 +339,7 @@ static irqreturn_t pcc_mbox_irq(int irq, void *p) * where the flag is set again to start new transfer. This is * required to avoid any possible race in updatation of this flag. */ - pchan->chan_in_use = false; + WRITE_ONCE(pchan->chan_in_use, false); if (!rc) mbox_chan_received_data(chan, NULL); mbox_chan_txdone(chan, rc);
@@ -471,7 +471,7 @@ static int pcc_send_data(struct mbox_chan *chan, void *data) ret = pcc_chan_reg_read_modify_write(&pchan->db); if (!ret && pchan->plat_irq > 0) - pchan->chan_in_use = true; + WRITE_ONCE(pchan->chan_in_use, true); return ret; }
--
2.43.0