linux-kernel - [PATCH v2 2/2] x86/platform/amd: replace down_timeout with down

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Message-Id: <20250605-amd-hsmp-v2-2-a811bc3dd74a@hillion.co.uk>
Date: Thu, 05 Jun 2025 19:09:27 +0100
From: Jake Hillion via B4 Relay <devnull+jake.hillion.co.uk@...nel.org>
To: Naveen Krishna Chatradhi <naveenkrishna.chatradhi@....com>, 
 Carlos Bilbao <carlos.bilbao@...nel.org>, 
 Hans de Goede <hdegoede@...hat.com>, 
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc: platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org, 
 sched-ext@...a.com, Jake Hillion <jake@...lion.co.uk>, 
 Suma Hegde <suma.hegde@....com>
Subject: [PATCH v2 2/2] x86/platform/amd: replace down_timeout with
 down_interruptible

From: Jake Hillion <jake@...lion.co.uk>

Currently hsmp_send_message uses down_timeout with a 100ms timeout to
take the semaphore. However __hsmp_send_message, the content of the
critical section, has a sleep in it. On systems with significantly
delayed scheduling behaviour this may take over 100ms.

Convert this method to down_interruptible. Leave the error handling the
same as the documentation currently is not specific about what error is
returned.

Previous behaviour: a caller who competes with another caller stuck in
the critical section due to scheduler delays would receive -ETIME.

New behaviour: a caller who competes with another caller stuck in the
critical section due to scheduler delays will complete successfully.

Reviewed-by: Suma Hegde <suma.hegde@....com>
Tested-by: Suma Hegde <suma.hegde@....com>
Signed-off-by: Jake Hillion <jake@...lion.co.uk>
---
 drivers/platform/x86/amd/hsmp/hsmp.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/drivers/platform/x86/amd/hsmp/hsmp.c b/drivers/platform/x86/amd/hsmp/hsmp.c
index f35c639457ac425e79dead2515c0eddea0759323..6c30bb3edc1d77939b10047b771a5c574e5f2a1e 100644
--- a/drivers/platform/x86/amd/hsmp/hsmp.c
+++ b/drivers/platform/x86/amd/hsmp/hsmp.c
@@ -216,13 +216,7 @@ int hsmp_send_message(struct hsmp_message *msg)
 		return -ENODEV;
 	sock = &hsmp_pdev.sock[msg->sock_ind];
 
-	/*
-	 * The time taken by smu operation to complete is between
-	 * 10us to 1ms. Sometime it may take more time.
-	 * In SMP system timeout of 100 millisecs should
-	 * be enough for the previous thread to finish the operation
-	 */
-	ret = down_timeout(&sock->hsmp_sem, msecs_to_jiffies(HSMP_MSG_TIMEOUT));
+	ret = down_interruptible(&sock->hsmp_sem);
 	if (ret < 0)
 		return ret;
 

-- 
2.47.2