wangchdo commented on PR #17018: URL: https://github.com/apache/nuttx/pull/17018#issuecomment-3290600160
> > The current syslog will alway log by rawstream, which will always firstly put the message to a buffer and then flush them by calling syslog_write(). syslog_write() will alway broadcast them to all channels. There are some drawbacks: > > ``` > > 1. The rawstream buffer is allocated in the caller's > > stack as temperory variable, which cause huge stack usage, > > this is not good for the platform wit limited resource > > ``` > > is 64byes buffer huge? > > > ``` > > 2. In interrupt context, syslog() will firstly put the message > > in a global buffer, using a spinlock to protect it, which will > > cause dead lock in some cases in multicore system, when > > doing syslog in exception context from interrupt > > ``` > > without this buffer, the interrupt log will make the normal log unreadable. Anyway, you can disable interrupt buffer if you don't want. > > > ``` > > 3. syslog_write() will always broadcast to all the channels, > > so it can only be used when all the channels are ready, making > > syslog() not able to be used at the early age during boot. > > ``` > > but the channel which isn't ready to log, should skip the action by calling https://github.com/apache/nuttx/blob/master/include/nuttx/init.h#L43-L48. > > > ``` > > 4. with some options enabled syslog() relies on kernel to be ready > > before it can be used, for example getting kernel > > state or timestamp and put them with the message, this will also make > > syslog() not able to work before kernel is ready. > > ``` > > nx_vsyslog already check the initialize state to avoid calling these functions too earlier. > > > This patch introduced LOG_CONSOLE_DEBUG priority to syslog(), which is implemented in a light-weight way: no buffering, unicast and no relying on kernel is ready. Calling syslog() with this priority the message will always be sent to console in a synchronous way, and users can use it as long as uart early initializing is completed, which is before nx_start() is called. > > basically, this api is used for early log, so it's better to contain early in the function to make the usage clear. Hi @xiaoxiang781216 I think new function added to syslog is not only for early stage, as I put in the commit message, it is for: 1. uinicast(log to serial) 2. synchronous 3. light-weight (no buffering, no spinlock, no flushing) 4. work at anytime(only after earlyserialint() is completed), 5. work at anywhere(task, interrupt, crash context, interrut nest task, crash nest interrup ....) So I think LOG_LOWPUT should be a better option, I just amended the patch updating LOG_CONSOLE_DEBUG to LOG_LOWPUT -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: commits-unsubscr...@nuttx.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
