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Date: Tue, 26 Jan 2010 18:20:28 -0500 From: Steven Rostedt <rostedt@...dmis.org> To: Frederic Weisbecker <fweisbec@...il.com> Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu> Subject: Re: [PATCH 1/5] tracing: Prevent kernel oops with corrupted buffer On Tue, 2010-01-26 at 23:39 +0100, Frederic Weisbecker wrote: > On Tue, Jan 26, 2010 at 02:32:23PM -0800, Andrew Morton wrote: > > > + if (WARN_ON_ONCE(pid < 0)) { > > > + strcpy(comm, "<XXX>"); > > > + return; > > > + } > > > + > > > if (pid > PID_MAX_DEFAULT) { > > > strcpy(comm, "<...>"); > > > return; > > > > But why is it WARN_ON_ONCE()? That will only fix the problem a single > > time. On the second occurrence, it will oops again. > > > > The warning will be produced only once, but after that, > the condition is still checked like a simple if: > > #define WARN_ON_ONCE(condition) ({ \ > static bool __warned; \ > int __ret_warn_once = !!(condition); \ > \ > if (unlikely(__ret_warn_once)) \ > if (WARN_ON(!__warned)) \ > __warned = true; \ > unlikely(__ret_warn_once); \ > }) > > > And since this function can be called anytime we have a trace > to print to the user, we don't want to encumber with thousands > of warnings. Exactly! -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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