linux-kernel - [PATCH 6/8] stm class: ftrace: Use different channel accroding to CPU

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Message-Id: <20201005071319.78508-7-alexander.shishkin@linux.intel.com>
Date:   Mon,  5 Oct 2020 10:13:17 +0300
From:   Alexander Shishkin <alexander.shishkin@...ux.intel.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Tingwei Zhang <tingwei@...eaurora.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: [PATCH 6/8] stm class: ftrace: Use different channel accroding to CPU

From: Tingwei Zhang <tingwei@...eaurora.org>

To avoid mixup of packets from differnt ftrace packets simultaneously,
use different channel for packets from different CPU.

Signed-off-by: Tingwei Zhang <tingwei@...eaurora.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
Signed-off-by: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
---
 drivers/hwtracing/stm/ftrace.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/stm/ftrace.c b/drivers/hwtracing/stm/ftrace.c
index c694a6e692d1..3bb606dfa634 100644
--- a/drivers/hwtracing/stm/ftrace.c
+++ b/drivers/hwtracing/stm/ftrace.c
@@ -37,8 +37,10 @@ static void notrace
 stm_ftrace_write(struct trace_export *export, const void *buf, unsigned int len)
 {
 	struct stm_ftrace *stm = container_of(export, struct stm_ftrace, ftrace);
+	/* This is called from trace system with preemption disabled */
+	unsigned int cpu = smp_processor_id();
 
-	stm_source_write(&stm->data, STM_FTRACE_CHAN, buf, len);
+	stm_source_write(&stm->data, STM_FTRACE_CHAN + cpu, buf, len);
 }
 
 static int stm_ftrace_link(struct stm_source_data *data)
@@ -63,6 +65,7 @@ static int __init stm_ftrace_init(void)
 {
 	int ret;
 
+	stm_ftrace.data.nr_chans = roundup_pow_of_two(num_possible_cpus());
 	ret = stm_source_register_device(NULL, &stm_ftrace.data);
 	if (ret)
 		pr_err("Failed to register stm_source - ftrace.\n");
-- 
2.28.0