linux-kernel - [PATCH RFC cpumask 1/5] cpumask: Un-inline cpulist

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Message-Id: <20210106004956.11961-1-paulmck@kernel.org>
Date:   Tue,  5 Jan 2021 16:49:52 -0800
From:   paulmck@...nel.org
To:     linux-kernel@...r.kernel.org
Cc:     peterz@...radead.org, yury.norov@...il.com, kernel-team@...com,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        "Paul E . McKenney" <paulmck@...nel.org>
Subject: [PATCH RFC cpumask 1/5] cpumask: Un-inline cpulist_parse for SMP; prepare for ascii helpers

From: Paul Gortmaker <paul.gortmaker@...driver.com>

In order to support convenience tokens like "all", and "none" and
"last" in CPU lists, we'll have to use string operations and expand
on what is currently a simple wrapper around the underlying bitmap
function call.

Rather than add header dependencies to cpumask.h and code more complex
operations not really appropriate for a header file, we prepare by
simply un-inlining it here and move it to the lib dir alongside the
other more complex cpumask functions.

Since lib/cpumask.c is built conditionally on CONFIG_SMP, and there
are non-SMP callers, we leave the one-line stub behind for that case.
If they want to check "0-0" is a valid range, they can still do it.
In the meantime, we can add the ascii helpers for CONFIG_SMP users.
The use of NR_CPUS vs. CONFIG_SMP is consistent with the existing file.

Aside from an additional exported symbol in the SMP case, no functional
changes are anticipated with this move.

Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 include/linux/cpumask.h |  8 ++++++++
 lib/cpumask.c           | 13 +++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 383684e..1f506e2 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -685,11 +685,19 @@ static inline int cpumask_parse(const char *buf, struct cpumask *dstp)
  * @dstp: the cpumask to set.
  *
  * Returns -errno, or 0 for success.
+ *
+ * There are instances of non-SMP callers of this, and the easiest way
+ * to remain 100% runtime compatible is to let them continue to have the
+ * one-line stub, while the SMP version in lib/cpumask.c gets improved.
  */
+#if NR_CPUS == 1
 static inline int cpulist_parse(const char *buf, struct cpumask *dstp)
 {
 	return bitmap_parselist(buf, cpumask_bits(dstp), nr_cpumask_bits);
 }
+#else
+int cpulist_parse(const char *buf, struct cpumask *dstp);
+#endif
 
 /**
  * cpumask_size - size to allocate for a 'struct cpumask' in bytes
diff --git a/lib/cpumask.c b/lib/cpumask.c
index 3592402..6e6e835 100644
--- a/lib/cpumask.c
+++ b/lib/cpumask.c
@@ -95,6 +95,19 @@ int cpumask_next_wrap(int n, const struct cpumask *mask, int start, bool wrap)
 }
 EXPORT_SYMBOL(cpumask_next_wrap);
 
+/**
+ * cpulist_parse - extract a cpumask from a user string of ranges
+ * @buf: the buffer to extract from
+ * @dstp: the cpumask to set.
+ *
+ * Returns -errno, or 0 for success.
+ */
+int cpulist_parse(const char *buf, struct cpumask *dstp)
+{
+	return bitmap_parselist(buf, cpumask_bits(dstp), nr_cpumask_bits);
+}
+EXPORT_SYMBOL(cpulist_parse);
+
 /* These are not inline because of header tangles. */
 #ifdef CONFIG_CPUMASK_OFFSTACK
 /**
-- 
2.9.5