From bfd8d3f23b51018388be0411ccbc2d56277fe294 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 9 Oct 2016 12:16:57 -0700 Subject: [PATCH] printk: make reading the kernel log flush pending lines That will mean that any possible subsequent continuation will now be broken up onto a line of its own (since reading the log has finalized the beginning og the line), but if user space has activated system logging (or if there's a kernel message dump going on) that is the right thing to do. And now that we actually get the continuation flags _right_ for this all, the user space logger that is reading the kernel messages can actually see the continuation marker. Not that anybody seems to really bother with it (or care), but in theory user space can do its own message stitching. Signed-off-by: Linus Torvalds --- kernel/printk/printk.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index f6fe60d725dd..170d3a8040f4 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -783,6 +783,8 @@ static ssize_t devkmsg_write(struct kiocb *iocb, struct iov_iter *from) return ret; } +static void cont_flush(void); + static ssize_t devkmsg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) { @@ -798,6 +800,7 @@ static ssize_t devkmsg_read(struct file *file, char __user *buf, if (ret) return ret; raw_spin_lock_irq(&logbuf_lock); + cont_flush(); while (user->seq == log_next_seq) { if (file->f_flags & O_NONBLOCK) { ret = -EAGAIN; @@ -860,6 +863,7 @@ static loff_t devkmsg_llseek(struct file *file, loff_t offset, int whence) return -ESPIPE; raw_spin_lock_irq(&logbuf_lock); + cont_flush(); switch (whence) { case SEEK_SET: /* the first record */ @@ -898,6 +902,7 @@ static unsigned int devkmsg_poll(struct file *file, poll_table *wait) poll_wait(file, &log_wait, wait); raw_spin_lock_irq(&logbuf_lock); + cont_flush(); if (user->seq < log_next_seq) { /* return error when data has vanished underneath us */ if (user->seq < log_first_seq) @@ -1284,6 +1289,7 @@ static int syslog_print(char __user *buf, int size) size_t skip; raw_spin_lock_irq(&logbuf_lock); + cont_flush(); if (syslog_seq < log_first_seq) { /* messages are gone, move to first one */ syslog_seq = log_first_seq; @@ -1343,6 +1349,7 @@ static int syslog_print_all(char __user *buf, int size, bool clear) return -ENOMEM; raw_spin_lock_irq(&logbuf_lock); + cont_flush(); if (buf) { u64 next_seq; u64 seq; @@ -1504,6 +1511,7 @@ int do_syslog(int type, char __user *buf, int len, int source) /* Number of chars in the log buffer */ case SYSLOG_ACTION_SIZE_UNREAD: raw_spin_lock_irq(&logbuf_lock); + cont_flush(); if (syslog_seq < log_first_seq) { /* messages are gone, move to first one */ syslog_seq = log_first_seq; @@ -3016,6 +3024,7 @@ void kmsg_dump(enum kmsg_dump_reason reason) dumper->active = true; raw_spin_lock_irqsave(&logbuf_lock, flags); + cont_flush(); dumper->cur_seq = clear_seq; dumper->cur_idx = clear_idx; dumper->next_seq = log_next_seq; @@ -3106,6 +3115,7 @@ bool kmsg_dump_get_line(struct kmsg_dumper *dumper, bool syslog, bool ret; raw_spin_lock_irqsave(&logbuf_lock, flags); + cont_flush(); ret = kmsg_dump_get_line_nolock(dumper, syslog, line, size, len); raw_spin_unlock_irqrestore(&logbuf_lock, flags); @@ -3148,6 +3158,7 @@ bool kmsg_dump_get_buffer(struct kmsg_dumper *dumper, bool syslog, goto out; raw_spin_lock_irqsave(&logbuf_lock, flags); + cont_flush(); if (dumper->cur_seq < log_first_seq) { /* messages are gone, move to first available one */ dumper->cur_seq = log_first_seq; -- 2.20.1