Messages in this thread | | | From | David Laight <> | Subject | RE: [PATCH 3/4] samples/bpf: Check the error of write() and read() | Date | Mon, 2 Jul 2018 09:25:11 +0000 |
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From: Taeung Song > Sent: 02 July 2018 10:15 > test_task_rename() and test_urandom_read() > can be failed during write() and read(), > So check the result of them. > > Signed-off-by: Taeung Song <treeze.taeung@gmail.com> > --- > samples/bpf/test_overhead_user.c | 20 +++++++++++++++----- > 1 file changed, 15 insertions(+), 5 deletions(-) > > diff --git a/samples/bpf/test_overhead_user.c b/samples/bpf/test_overhead_user.c > index 6caf47a..8a88d9c 100644 > --- a/samples/bpf/test_overhead_user.c > +++ b/samples/bpf/test_overhead_user.c > @@ -6,6 +6,7 @@ > */ > #define _GNU_SOURCE > #include <sched.h> > +#include <errno.h> > #include <stdio.h> > #include <sys/types.h> > #include <asm/unistd.h> > @@ -44,8 +45,12 @@ static void test_task_rename(int cpu) > exit(1); > } > start_time = time_get_ns(); > - for (i = 0; i < MAX_CNT; i++) > - write(fd, buf, sizeof(buf)); > + for (i = 0; i < MAX_CNT; i++) { > + if (write(fd, buf, sizeof(buf)) < 0) { > + printf("task rename failed: %s\n", strerror(errno)); > + break;
I'm not sure 'break' generates sensible output.
> + } > + }
What about partial writes??
> printf("task_rename:%d: %lld events per sec\n", > cpu, MAX_CNT * 1000000000ll / (time_get_ns() - start_time)); > close(fd); > @@ -55,7 +60,7 @@ static void test_urandom_read(int cpu) > { > __u64 start_time; > char buf[4]; > - int i, fd; > + int i, fd, err = 0; > > fd = open("/dev/urandom", O_RDONLY); > if (fd < 0) { > @@ -63,8 +68,13 @@ static void test_urandom_read(int cpu) > exit(1); > } > start_time = time_get_ns(); > - for (i = 0; i < MAX_CNT; i++) > - read(fd, buf, sizeof(buf)); > + for (i = 0; i < MAX_CNT; i++) { > + err = read(fd, buf, sizeof(buf)); > + if (err < 0 || err >= sizeof(buf)) {
Overlong reads indicate that something is seriously awry. Short reads are valid - but maybe not expected. > + printf("failed to read from /dev/urandom: %s\n", strerror(errno));
strerror() won't give anything sensible unless err == -1; You probably want to include the loop count.
> + break;
The summary print will be gibberish after break.
> + } > + } > printf("urandom_read:%d: %lld events per sec\n", > cpu, MAX_CNT * 1000000000ll / (time_get_ns() - start_time)); > close(fd); > -- > 2.7.4
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