linux-kernel - [PATCH] tools/rtla: Do not stop user-space if a cpu is offline

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Date:   Fri, 15 Sep 2023 15:02:32 +0200
From:   Daniel Bristot de Oliveira <bristot@...nel.org>
To:     Daniel Bristot de Oliveira <bristot@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] tools/rtla: Do not stop user-space if a cpu is offline

If no CPU list is passed, timerlat in user-space will dispatch
one thread per sysconf(_SC_NPROCESSORS_CONF). However, not all
CPU might be available, for instance, if HT is disabled.

Currently, rtla timerlat is stopping the session if an user-space
thread cannot set affinity to a CPU, or if a running user-space
thread is killed. However, this is too restrictive.

So, reduce the error to a debug message, and rtla timerlat run as
long as there is at least one user-space thread alive.

Fixes: cdca4f4e5e8e ("rtla/timerlat_top: Add timerlat user-space support")
Signed-off-by: Daniel Bristot de Oliveira <bristot@...nel.org>
---
 tools/tracing/rtla/src/timerlat_u.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/tracing/rtla/src/timerlat_u.c b/tools/tracing/rtla/src/timerlat_u.c
index 05e310696dd5..01dbf9a6b5a5 100644
--- a/tools/tracing/rtla/src/timerlat_u.c
+++ b/tools/tracing/rtla/src/timerlat_u.c
@@ -45,7 +45,7 @@ static int timerlat_u_main(int cpu, struct timerlat_u_params *params)
 
 	retval = sched_setaffinity(gettid(), sizeof(set), &set);
 	if (retval == -1) {
-		err_msg("Error setting user thread affinity\n");
+		debug_msg("Error setting user thread affinity %d, is the CPU online?\n", cpu);
 		exit(1);
 	}
 
@@ -193,7 +193,9 @@ void *timerlat_u_dispatcher(void *data)
 					procs_count--;
 				}
 			}
-			break;
+
+			if (!procs_count)
+				break;
 		}
 
 		sleep(1);
-- 
2.38.1