@@ -175,12 +175,15 @@ static void start_transaction(struct acpi_ec *ec)
acpi_ec_write_cmd(ec, ec->curr->command);
}
-static void advance_transaction(struct acpi_ec *ec, u8 status)
+static void advance_transaction(struct acpi_ec *ec)
{
unsigned long flags;
struct transaction *t;
+ u8 status;
spin_lock_irqsave(&ec->lock, flags);
+ pr_debug("===== %s =====\n", in_interrupt() ? "IRQ" : "TASK");
+ status = acpi_ec_read_status(ec);
t = ec->curr;
if (!t)
goto unlock;
@@ -243,7 +246,7 @@ static int ec_poll(struct acpi_ec *ec)
msecs_to_jiffies(1)))
return 0;
}
- advance_transaction(ec, acpi_ec_read_status(ec));
+ advance_transaction(ec);
} while (time_before(jiffies, delay));
pr_debug(PREFIX "controller reset, restart transaction\n");
spin_lock_irqsave(&ec->lock, flags);
@@ -662,11 +665,8 @@ static u32 acpi_ec_gpe_handler(acpi_handle gpe_device,
u32 gpe_number, void *data)
{
struct acpi_ec *ec = data;
- u8 status = acpi_ec_read_status(ec);
-
- pr_debug(PREFIX "~~~> interrupt, status:0x%02x\n", status);
- advance_transaction(ec, status);
+ advance_transaction(ec);
if (ec_transaction_done(ec) &&
(acpi_ec_read_status(ec) & ACPI_EC_FLAG_IBF) == 0) {
wake_up(&ec->wait);
This is a note to let you know that I have just added a patch titled ACPI / EC: Avoid race condition related to advance_transaction() to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.11.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From ebdac73096373fbd90146f0858ff968cba62d726 Mon Sep 17 00:00:00 2001 From: Lv Zheng <lv.zheng@intel.com> Date: Sun, 15 Jun 2014 08:41:17 +0800 Subject: [PATCH 18/41] ACPI / EC: Avoid race condition related to advance_transaction() commit 66b42b78bc1e816f92b662e8888c89195e4199e1 upstream. The advance_transaction() will be invoked from the IRQ context GPE handler and the task context ec_poll(). The handling of this function is locked so that the EC state machine are ensured to be advanced sequentially. But there is a problem. Before invoking advance_transaction(), EC_SC(R) is read. Then for advance_transaction(), there could be race condition around the lock from both contexts. The first one reading the register could fail this race and when it passes the stale register value to the state machine advancement code, the hardware condition is totally different from when the register is read. And the hardware accesses determined from the wrong hardware status can break the EC state machine. And there could be cases that the functionalities of the platform firmware are seriously affected. For example: 1. When 2 EC_DATA(W) writes compete the IBF=0, the 2nd EC_DATA(W) write may be invalid due to IBF=1 after the 1st EC_DATA(W) write. Then the hardware will either refuse to respond a next EC_SC(W) write of the next command or discard the current WR_EC command when it receives a EC_SC(W) write of the next command. 2. When 1 EC_SC(W) write and 1 EC_DATA(W) write compete the IBF=0, the EC_DATA(W) write may be invalid due to IBF=1 after the EC_SC(W) write. The next EC_DATA(R) could never be responded by the hardware. This is the root cause of the reported issue. Fix this issue by moving the EC_SC(R) access into the lock so that we can ensure that the state machine is advanced consistently. Link: https://bugzilla.kernel.org/show_bug.cgi?id=70891 Link: https://bugzilla.kernel.org/show_bug.cgi?id=63931 Link: https://bugzilla.kernel.org/show_bug.cgi?id=59911 Reported-and-tested-by: Gareth Williams <gareth@garethwilliams.me.uk> Reported-and-tested-by: Hans de Goede <jwrdegoede@fedoraproject.org> Reported-by: Barton Xu <tank.xuhan@gmail.com> Tested-by: Steffen Weber <steffen.weber@gmail.com> Tested-by: Arthur Chen <axchen@nvidia.com> Signed-off-by: Lv Zheng <lv.zheng@intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> [ luis: backported to 3.11: adjusted context ] Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- drivers/acpi/ec.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) -- 1.9.1