[PATCH 5/5] os: don't block signal-unsafe logging, merely warn about it.

[Peter Hutterer]

On Thu, Aug 16, 2012 at 08:20:33AM -0700, Chase Douglas wrote:
> On 08/15/2012 09:52 PM, Peter Hutterer wrote:
> >Throw an error into the log file, but continue anyway. And after three
> >warnings, stop complaining. Not all input drivers will be fixed in time (or
> >ever) and our printf implementation is vastly inferior, so there is still a
> >use-case for non-sigsafe logging.
> >
> >This also adds more linebreaks to the message.
> >
> >CC: Chase Douglas <chase.douglas at canonical.com>
> >Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
> >---
> >  os/log.c | 39 +++++++++++++++++++++++++--------------
> >  1 file changed, 25 insertions(+), 14 deletions(-)
> >
> >diff --git a/os/log.c b/os/log.c
> >index 4348739..7fca317 100644
> >--- a/os/log.c
> >+++ b/os/log.c
> >@@ -467,6 +467,7 @@ LogMessageTypeVerbString(MessageType type, int verb)
> >  void
> >  LogVMessageVerb(MessageType type, int verb, const char *format, va_list args)
> >  {
> >+    static unsigned int warned;
> >      const char *type_str;
> >      char buf[1024];
> >      const size_t size = sizeof(buf);
> >@@ -474,13 +475,17 @@ LogVMessageVerb(MessageType type, int verb, const char *format, va_list args)
> >      size_t len = 0;
> >
> >      if (inSignalContext) {
> >-        BUG_WARN_MSG(inSignalContext,
> >-                     "Warning: attempting to log data in a signal unsafe "
> >-                     "manner while in signal context. Please update to check "
> >-                     "inSignalContext and/or use LogMessageVerbSigSafe() or "
> >-                     "ErrorFSigSafe(). The offending log format message is:\n"
> >-                     "%s\n", format);
> >-        return;
> >+        if (warned < 3) {
> >+            BUG_WARN_MSG(inSignalContext,
> >+                         "Warning: attempting to log data in a signal unsafe "
> >+                         "manner while in signal context.\nPlease update to check "
> >+                         "inSignalContext and/or use LogMessageVerbSigSafe() or "
> >+                         "ErrorFSigSafe().\nThe offending log format message is:\n"
> >+                         "%s\n", format);
> >+            warned++;
> >+            if (warned == 3)
> >+                LogMessageVerbSigSafe(X_WARNING, -1, "Warned %u times about sigsafe logging. Will be quiet now.\n", warned);
> >+        }
> >      }
> >
> >      type_str = LogMessageTypeVerbString(type, verb);
> >@@ -566,6 +571,7 @@ void
> >  LogVHdrMessageVerb(MessageType type, int verb, const char *msg_format,
> >                     va_list msg_args, const char *hdr_format, va_list hdr_args)
> >  {
> >+    static unsigned int warned;
> >      const char *type_str;
> >      char buf[1024];
> >      const size_t size = sizeof(buf);
> >@@ -573,15 +579,20 @@ LogVHdrMessageVerb(MessageType type, int verb, const char *msg_format,
> >      size_t len = 0;
> >
> >      if (inSignalContext) {
> >-        BUG_WARN_MSG(inSignalContext,
> >-                     "Warning: attempting to log data in a signal unsafe "
> >-                     "manner while in signal context. Please update to check "
> >-                     "inSignalContext and/or use LogMessageVerbSigSafe(). The "
> >-                     "offending header and log message formats are:\n%s %s\n",
> >-                     hdr_format, msg_format);
> >-        return;
> >+        if (warned < 3) {
> >+            BUG_WARN_MSG(inSignalContext,
> >+                         "Warning: attempting to log data in a signal unsafe "
> >+                         "manner while in signal context.\nPlease update to check "
> >+                         "inSignalContext and/or use LogMessageVerbSigSafe().\nThe "
> >+                         "offending header and log message formats are:\n%s %s\n",
> >+                         hdr_format, msg_format);
> >+            warned++;
> >+            if (warned == 3)
> >+                LogMessageVerbSigSafe(X_WARNING, -1, "Warned %u times about sigsafe logging. Will be quiet now.\n", warned);
> >+        }
> >      }
> >
> >+
> 
> Stray newline here ^^
> 
> >      type_str = LogMessageTypeVerbString(type, verb);
> >      if (!type_str)
> >          return;
> >
> 
> It's too bad everything won't be fixed in time, but we've gotten
> along this far without too much issue. Hopefully the warnings will
> be big enough to force the issue to a close.

there are _a lot_ of debugging messages in drivers, and some of those
drivers are unmaintained but continue to run anyway. the real issiue is that
the current implementation of pnprintf doesn't even come close to the real
one. no length modifiers, only few conversion specifiers, etc.

so we'd have to go through and audit every single ErrorF, DBG, xf86*Msg*,
etc. in the drivers. that's going to take a while.

> Reviewed-by: Chase Douglas <chase.douglas at canonical.com>

Thanks.

Cheers,
   Peter