On (09/13/18 23:28), Sergey Senozhatsky wrote: > Not that I see any problems with pr_line_flush(). But can drop it, sure. > pr_line() is a replacement for pr_cont() and as such it's not for multi-line > buffering.
OK, attached. Let me know if anything needs to improved (including broken English). Will we keep in the printk tree or shall I send a formal patch to Andrew? === From: Sergey Senozhatsky <[email protected]> Subject: [PATCH] lib/seq_buf: add pr_line buffering API Signed-off-by: Sergey Senozhatsky <[email protected]> --- include/linux/kern_levels.h | 3 ++ include/linux/seq_buf.h | 60 +++++++++++++++++++++++++++++++++++++ lib/seq_buf.c | 57 +++++++++++++++++++++++++++++++++++ 3 files changed, 120 insertions(+) diff --git a/include/linux/kern_levels.h b/include/linux/kern_levels.h index d237fe854ad9..9c281ac745b3 100644 --- a/include/linux/kern_levels.h +++ b/include/linux/kern_levels.h @@ -20,6 +20,9 @@ * Annotation for a "continued" line of log printout (only done after a * line that had no enclosing \n). Only to be used by core/arch code * during early bootup (a continued line is not SMP-safe otherwise). + * + * Please consider pr_line()/vpr_line() functions for SMP-safe continued + * line printing. */ #define KERN_CONT KERN_SOH "c" diff --git a/include/linux/seq_buf.h b/include/linux/seq_buf.h index aa5deb041c25..b33aeea14803 100644 --- a/include/linux/seq_buf.h +++ b/include/linux/seq_buf.h @@ -23,6 +23,62 @@ struct seq_buf { loff_t readpos; }; +#define __SEQ_BUF_INITIALIZER(buf, length) \ +{ \ + .buffer = (buf), \ + .size = (length), \ + .len = 0, \ + .readpos = 0, \ +} + +#ifdef CONFIG_PRINTK +#define __PR_LINE_BUF_SZ 80 +#else +#define __PR_LINE_BUF_SZ 0 +#endif + +/** + * pr_line - printk() line buffer structure + * @sb: underlying seq buffer, which holds the data + * @level: printk() log level (KERN_ERR, etc.) + */ +struct pr_line { + struct seq_buf sb; + char *level; +}; + +/** + * DEFINE_PR_LINE - define a new pr_line variable + * @lev: printk() log level + * @name: variable name + * + * Defines a new pr_line varialbe, which would use an implicit + * stack buffer of size __PR_LINE_BUF_SZ. + */ +#define DEFINE_PR_LINE(lev, name) \ + char __line_##name[__PR_LINE_BUF_SZ]; \ + struct pr_line name = { \ + .sb = __SEQ_BUF_INITIALIZER(__line_##name, \ + __PR_LINE_BUF_SZ), \ + .level = lev, \ + } + +/** + * DEFINE_PR_LINE_BUF - define a new pr_line variable + * @lev: printk() log level + * @name: variable name + * @buf: external buffer + * @sz: external buffer size + * + * Defines a new pr_line variable, which would use an external + * buffer for printk line. + */ +#define DEFINE_PR_LINE_BUF(lev, name, buf, sz) \ + struct pr_line name = { \ + .sb = __SEQ_BUF_INITIALIZER(buf, (sz)), \ + .level = lev, \ + } + static inline void seq_buf_clear(struct seq_buf *s) { s->len = 0; @@ -131,4 +187,8 @@ extern int seq_buf_bprintf(struct seq_buf *s, const char *fmt, const u32 *binary); #endif +extern __printf(2, 0) +int vpr_line(struct pr_line *pl, const char *fmt, va_list args); +extern __printf(2, 3) +int pr_line(struct pr_line *pl, const char *fmt, ...); #endif /* _LINUX_SEQ_BUF_H */ diff --git a/lib/seq_buf.c b/lib/seq_buf.c index 11f2ae0f9099..fada7623f168 100644 --- a/lib/seq_buf.c +++ b/lib/seq_buf.c @@ -324,3 +324,60 @@ int seq_buf_to_user(struct seq_buf *s, char __user *ubuf, int cnt) s->readpos += cnt; return cnt; } + +/** + * vpr_line - Append data to the printk() line buffer + * @pl: the pr_line descriptor + * @fmt: printf format string + * @args: va_list of arguments from a printf() type function + * + * Writes a vnprintf() format into the printk() pr_line buffer. + * Terminating new-line symbol flushes (prints) the buffer. + * + * Unlike pr_cont() and printk(KERN_CONT), this function is SMP-safe + * and shall be used for continued line printing. + * + * Returns zero on success, -1 on overflow. + */ +int vpr_line(struct pr_line *pl, const char *fmt, va_list args) +{ + struct seq_buf *s = &pl->sb; + int ret, len; + + ret = seq_buf_vprintf(s, fmt, args); + + len = seq_buf_used(s); + if (len && s->buffer[len - 1] == '\n') { + printk("%s%.*s", pl->level ? : KERN_DEFAULT, len, s->buffer); + seq_buf_clear(s); + } + + return ret; +} +EXPORT_SYMBOL(vpr_line); + +/** + * pr_line - Append data to the printk() line buffer + * @pl: the pr_line descriptor + * @fmt: printf format string + * + * Writes a printf() format into the printk() pr_line buffer. + * Terminating new-line symbol flushes (prints) the buffer. + * + * Unlike pr_cont() and printk(KERN_CONT), this function is SMP-safe + * and shall be used for continued line printing. + * + * Returns zero on success, -1 on overflow. + */ +int pr_line(struct pr_line *pl, const char *fmt, ...) +{ + va_list ap; + int ret; + + va_start(ap, fmt); + ret = vpr_line(pl, fmt, ap); + va_end(ap); + + return ret; +} +EXPORT_SYMBOL(pr_line); -- 2.19.0
