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bpf: selftests: handle sparse CPU allocations

PATCH In review Martynas Pumputis 3 participants 3 messages Jan 31, 2019

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Networking Network drivers Kselftest BPF +1 more subsystems
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Martynas Pumputis

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#0 lore raw

PATCH v2 1/1 bpf: selftests: handle sparse CPU allocations

Previously, bpf_num_possible_cpus() had a bug when calculating a number of possible CPUs in the case of sparse CPU allocations, as it was considering only the first range or element of /sys/devices/system/cpu/possible.

E.g. in the case of "0,2-3" (CPU 1 is not available), the function returned 1 instead of 3.

This patch fixes the function by making it parse all CPU ranges and elements.

Signed-off-by Martynas Pumputis <[email protected]>

---
Testing of the patch: https://gist.github.com/brb/5369b5cfd08babb80cf2c4081dc19762

---
 tools/testing/selftests/bpf/bpf_util.h | 31 +++++++++++++++++---------
 1 file changed, 21 insertions(+), 10 deletions(-)
tools/testing/selftests/bpf/bpf_util.h +21 -10
index 315a44fa32af..442c3ab2d688 100644
@@ -9,11 +9,12 @@
 
 static inline unsigned int bpf_num_possible_cpus(void)
 {
+
 	static const char *fcpu = "/sys/devices/system/cpu/possible";
 	unsigned int start, end, possible_cpus = 0;
 	char buff[128];
 	FILE *fp;
-	int n;
+	int len, n, i, j = 0;
 
 	fp = fopen(fcpu, "r");
 	if (!fp) {

@@ -21,17 +22,27 @@ static inline unsigned int bpf_num_possible_cpus(void)
 		exit(1);
 	}
 
-	while (fgets(buff, sizeof(buff), fp)) {
-		n = sscanf(buff, "%u-%u", &start, &end);
-		if (n == 0) {
-			printf("Failed to retrieve # possible CPUs!\n");
-			exit(1);
-		} else if (n == 1) {
-			end = start;
+	if (!fgets(buff, sizeof(buff), fp)) {
+		printf("Failed to read %s!\n", fcpu);
+		exit(1);
+	}
+
+	len = strlen(buff);
+	for (i = 0; i <= len; i++) {
+		if (buff[i] == ',' || buff[i] == '\0') {
+			buff[i] = '\0';
+			n = sscanf(&buff[j], "%u-%u", &start, &end);
+			if (n <= 0) {
+				printf("Failed to retrieve # possible CPUs!\n");
+				exit(1);
+			} else if (n == 1) {
+				end = start;
+			}
+			possible_cpus += end - start + 1;
+			j = i + 1;
 		}
-		possible_cpus = start == 0 ? end + 1 : 0;
-		break;
 	}
+
 	fclose(fp);
 
 	return possible_cpus;
Signature · 1 line
2.20.1
Acked-by Yonghong Song on v2 1/1
#1 lore raw
Quoted 6 lines · Martynas Pumputis

Previously, bpf_num_possible_cpus() had a bug when calculating a number of possible CPUs in the case of sparse CPU allocations, as it was considering only the first range or element of /sys/devices/system/cpu/possible.

Quoted 7 lines

E.g. in the case of "0,2-3" (CPU 1 is not available), the function returned 1 instead of 3.

This patch fixes the function by making it parse all CPU ranges and elements.

Signed-off-by Martynas Pumputis <[email protected]>
Acked-by Yonghong Song <[email protected]>
maintainer
#2 lore raw
In reply to Martynas Pumputis
Quoted 24 lines · Martynas Pumputis

Previously, bpf_num_possible_cpus() had a bug when calculating a number of possible CPUs in the case of sparse CPU allocations, as it was considering only the first range or element of /sys/devices/system/cpu/possible.

E.g. in the case of "0,2-3" (CPU 1 is not available), the function returned 1 instead of 3.

This patch fixes the function by making it parse all CPU ranges and elements.

Signed-off-by Martynas Pumputis <[email protected]>

---
Testing of the patch: https://gist.github.com/brb/5369b5cfd08babb80cf2c4081dc19762

---
 tools/testing/selftests/bpf/bpf_util.h | 31 +++++++++++++++++---------
 1 file changed, 21 insertions(+), 10 deletions(-)
tools/testing/selftests/bpf/bpf_util.h +0 -0
index 315a44fa32af..442c3ab2d688 100644

tools/testing/selftests/bpf/bpf_util.h line 13

Quoted 5 lines
tools/testing/selftests/bpf/bpf_util.h +1 -0
@@ -9,11 +9,12 @@
 
 static inline unsigned int bpf_num_possible_cpus(void)
 {
+
 	static const char *fcpu = "/sys/devices/system/cpu/possible";

Applied and removed above whitespace while at it, thanks!