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tracing: Ensure trace buffer is at least 4096 bytes large
[ Upstream commit 7acf3a127b
]
Booting the kernel with 'trace_buf_size=1' give a warning at
boot during the ftrace selftests:
[ 0.892809] Running postponed tracer tests:
[ 0.892893] Testing tracer function:
[ 0.901899] Callback from call_rcu_tasks_trace() invoked.
[ 0.983829] Callback from call_rcu_tasks_rude() invoked.
[ 1.072003] .. bad ring buffer .. corrupted trace buffer ..
[ 1.091944] Callback from call_rcu_tasks() invoked.
[ 1.097695] PASSED
[ 1.097701] Testing dynamic ftrace: .. filter failed count=0 ..FAILED!
[ 1.353474] ------------[ cut here ]------------
[ 1.353478] WARNING: CPU: 0 PID: 1 at kernel/trace/trace.c:1951 run_tracer_selftest+0x13c/0x1b0
Therefore enforce a minimum of 4096 bytes to make the selftest pass.
Link: https://lkml.kernel.org/r/20220214134456.1751749-1-svens@linux.ibm.com
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
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1 changed files with 6 additions and 4 deletions
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@ -1496,10 +1496,12 @@ static int __init set_buf_size(char *str)
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if (!str)
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return 0;
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buf_size = memparse(str, &str);
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/* nr_entries can not be zero */
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if (buf_size == 0)
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return 0;
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trace_buf_size = buf_size;
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/*
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* nr_entries can not be zero and the startup
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* tests require some buffer space. Therefore
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* ensure we have at least 4096 bytes of buffer.
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*/
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trace_buf_size = max(4096UL, buf_size);
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return 1;
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}
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__setup("trace_buf_size=", set_buf_size);
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