linux-kernel - [PATCH 2/7] CXL: Add timeout to process element commands

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Message-Id: <1418026681-14787-2-git-send-email-imunsie@au.ibm.com>
Date:	Mon,  8 Dec 2014 19:17:56 +1100
From:	"Ian Munsie" <imunsie@....ibm.com>
To:	mpe <mpe@...erman.id.au>
Cc:	greg <greg@...ah.com>, arnd <arnd@...db.de>,
	benh <benh@...nel.crashing.org>, mikey <mikey@...ling.org>,
	anton <anton@...ba.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linuxppc-dev <linuxppc-dev@...abs.org>, jk <jk@...abs.org>,
	imunsie <imunsie@....ibm.com>,
	cbe-oss-dev <cbe-oss-dev@...ts.ozlabs.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: [PATCH 2/7] CXL: Add timeout to process element commands

From: Ian Munsie <imunsie@....ibm.com>

In the event that something goes wrong in the hardware and it is unable
to complete a process element comment we would end up polling forever,
effectively making the associated process unkillable.

This patch adds a timeout to the process element command code path, so
that we will give up if the hardware does not respond in a reasonable
time.

Signed-off-by: Ian Munsie <imunsie@....ibm.com>
---
 drivers/misc/cxl/native.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/misc/cxl/native.c b/drivers/misc/cxl/native.c
index 1001cf4..f2b37b4 100644
--- a/drivers/misc/cxl/native.c
+++ b/drivers/misc/cxl/native.c
@@ -277,6 +277,7 @@ static int do_process_element_cmd(struct cxl_context *ctx,
 				  u64 cmd, u64 pe_state)
 {
 	u64 state;
+	unsigned long timeout = jiffies + (HZ * CXL_TIMEOUT);
 
 	WARN_ON(!ctx->afu->enabled);
 
@@ -286,6 +287,10 @@ static int do_process_element_cmd(struct cxl_context *ctx,
 	smp_mb();
 	cxl_p1n_write(ctx->afu, CXL_PSL_LLCMD_An, cmd | ctx->pe);
 	while (1) {
+		if (time_after_eq(jiffies, timeout)) {
+			dev_warn(&ctx->afu->dev, "WARNING: Process Element Command timed out!\n");
+			return -EBUSY;
+		}
 		state = be64_to_cpup(ctx->afu->sw_command_status);
 		if (state == ~0ULL) {
 			pr_err("cxl: Error adding process element to AFU\n");
-- 
2.1.3

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