On 05.09.19 12:39, Janosch Frank wrote:
> Linemode seems to add a newline for each sent message which makes
> reading rather hard. Hence we add a small buffer and only print if
> it's full or a newline is encountered. Except for when the string is
> longer than the buffer, then we flush the buffer and print directly.
>
> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
> Reviewed-by: Thomas Huth <thuth@xxxxxxxxxx>
> ---
> lib/s390x/sclp-console.c | 70 +++++++++++++++++++++++++++++++++++++---
> 1 file changed, 66 insertions(+), 4 deletions(-)
>
> diff --git a/lib/s390x/sclp-console.c b/lib/s390x/sclp-console.c
> index 19416b5..7397dc1 100644
> --- a/lib/s390x/sclp-console.c
> +++ b/lib/s390x/sclp-console.c
> @@ -13,6 +13,7 @@
> #include <asm/page.h>
> #include <asm/arch_def.h>
> #include <asm/io.h>
> +#include <asm/spinlock.h>
> #include "sclp.h"
>
> /*
> @@ -87,6 +88,10 @@ static uint8_t _ascebc[256] = {
> 0x90, 0x3F, 0x3F, 0x3F, 0x3F, 0xEA, 0x3F, 0xFF
> };
>
> +static char lm_buff[120];
Just wondering, how did you come up with the 120? (my first guess would
have been something around 80)
> +static unsigned char lm_buff_off;
> +static struct spinlock lm_buff_lock;
> +
> static void sclp_print_ascii(const char *str)
> {
> int len = strlen(str);
> @@ -103,10 +108,10 @@ static void sclp_print_ascii(const char *str)
> sclp_service_call(SCLP_CMD_WRITE_EVENT_DATA, sccb);
> }
>
> -static void sclp_print_lm(const char *str)
> +static void lm_print(const char *buff, int len)
> {
The rename of str->buff could have been avoided, however, the impact is
rather small.
> unsigned char *ptr, *end, ch;
> - unsigned int count, offset, len;
> + unsigned int count, offset;
> struct WriteEventData *sccb;
> struct mdb *mdb;
> struct mto *mto;
> @@ -117,11 +122,10 @@ static void sclp_print_lm(const char *str)
> end = (unsigned char *) sccb + 4096 - 1;
> memset(sccb, 0, sizeof(*sccb));
> ptr = (unsigned char *) &sccb->msg.mdb.mto;
> - len = strlen(str);
> offset = 0;
> do {
> for (count = sizeof(*mto); offset < len; count++) {
> - ch = str[offset++];
> + ch = buff[offset++];
> if (ch == 0x0a || ptr + count > end)
> break;
> ptr[count] = _ascebc[ch];
> @@ -148,6 +152,64 @@ static void sclp_print_lm(const char *str)
> sclp_service_call(SCLP_CMD_WRITE_EVENT_DATA, sccb);
> }
>
> +
> +/*
> + * In contrast to the ascii console, linemode produces a new
> + * line with every write of data. The report() function uses
> + * several printf() calls to generate a line of data which
> + * would all end up on different lines.
> + *
> + * Hence we buffer here until we encounter a \n or the buffer
> + * is full. That means that linemode output can look a bit
> + * different from ascii and that it takes a bit longer for
> + * lines to appear.
> + */
> +static void sclp_print_lm(const char *str)
> +{
> + int len;
> + char *nl;
> +
> + spin_lock(&lm_buff_lock);
> +
> + len = strlen(str);
You could do that directly when declaring the variable, doesn't have to
be under the lock.
> + /*
> + * No use in copying into lm_buff, its time to flush the
> + * buffer and print str until finished.
> + */
> + if (len > sizeof(lm_buff)) {
I find ARRAY_SIZE(lm_buf) easier to understand than sizeof(lm_buff)
> + if (lm_buff_off)
> + lm_print(lm_buff, lm_buff_off);
> + lm_print(str, len);
> + memset(lm_buff, 0 , sizeof(lm_buff));
> + lm_buff_off = 0;
> + goto out;
> + }
> +
> +fill:
Is there a way to remove this goto by using a simple while loop?
> + len = len < (sizeof(lm_buff) - lm_buff_off) ? len : (sizeof(lm_buff) - lm_buff_off);
> + if ((lm_buff_off < sizeof(lm_buff) - 1)) {
Drop one set of ()
> + memcpy(&lm_buff[lm_buff_off], str, len);
> + lm_buff_off += len;
> + }
> + /* Buffer not full and no newline */
> + nl = strchr(lm_buff, '\n');
Why do we have to search? Shouldn't a newline be the last copied
character only?
> + if (lm_buff_off != sizeof(lm_buff) - 1 && !nl)
> + goto out;
> +
> + lm_print(lm_buff, lm_buff_off);
> + memset(lm_buff, 0 , sizeof(lm_buff));
> + lm_buff_off = 0;
> +
> + if (len < strlen(str)) {
> + str = &str[len];
> + len = strlen(str);
> + goto fill;
> + }
This looks too complicated for my taste :) Or my caffeine level is low.
I think we have the following cases:
1. String contains newline
a) String fits into remaining buffer
-> Copy into buffer, flush (last character is newline)
b) String doesn't fit into remaining buffer
-> Simply flush old buffer and print remaining string?
2. String doesn't contain newline.
a) String fits into remaining buffer
-> Copy into buffer, flush if full
b) String doesn't fit into remaining buffer
-> Simply flush old buffer and print remaining string?
Optimizing for 1b) or 2b) isn't really worth it I guess - unless we want
to wrap *any* string at 120 characters. But then, your pre-loop handling
would also have to be modified. I think this allow to simplify your code
a lot.
(how often does it happen in our current tests that we exceed 120
characters?)
> +
> +out:
> + spin_unlock(&lm_buff_lock);
> +}
> +
> /*
> * SCLP needs to be initialized by setting a send and receive mask,
> * indicating which messages the control program (we) want(s) to
>
--
Thanks,
David / dhildenb
