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[82.239.227.177]) by smtp.gmail.com with ESMTPSA id 194sm14359833wmh.19.2015.11.09.05.39.23 (version=TLSv1 cipher=RC4-SHA bits=128/128); Mon, 09 Nov 2015 05:39:24 -0800 (PST) Date: Mon, 9 Nov 2015 14:39:05 +0100 From: Adrien Mazarguil To: Bruce Richardson Message-ID: <20151109133905.GL4013@6wind.com> Mail-Followup-To: Bruce Richardson , Stephen Hemminger , Thomas Monjalon , dev@dpdk.org References: <1441811374-28984-1-git-send-email-bruce.richardson@intel.com> <1446552059-5446-1-git-send-email-bruce.richardson@intel.com> <1446552059-5446-3-git-send-email-bruce.richardson@intel.com> <4698587.GS9blBozDC@xps13> <20151104102418.GN3518@6wind.com> <20151104103957.4cabd090@xeon-e3> <20151105150918.GV3518@6wind.com> <20151106171007.GB19512@bricha3-MOBL3> <20151106172227.GC19512@bricha3-MOBL3> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151106172227.GC19512@bricha3-MOBL3> Cc: dev@dpdk.org Subject: Re: [dpdk-dev] [PATCH v3 2/4] ethdev: move error checking macros to header X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 09 Nov 2015 13:39:25 -0000 On Fri, Nov 06, 2015 at 05:22:27PM +0000, Bruce Richardson wrote: > On Fri, Nov 06, 2015 at 05:10:07PM +0000, Bruce Richardson wrote: > > On Thu, Nov 05, 2015 at 04:09:18PM +0100, Adrien Mazarguil wrote: > > > > > > I won't argue against this as it's obviously more complex than the original > > > method, however note that users of the RTE_PMD_DEBUG_TRACE() macro do not > > > have to modify their code. They shouldn't care about the implementation. > > > > > > Also note that we can do much cleaner code if we drop the all macros > > > implementation using a (much easier to debug) static inline function, > > > only perhaps with a wrapper macro that provides __LINE__, __func__ and > > > __FILE__ as arguments. Nontrival code shouldn't be done in macros anyway. > > > > > Getting something working with __FILE__ and probably __LINE__ would be easy enough > > with a helper macro, but __func__ is not so easy as it's not a preprocessor symbol > > [since the pre-processor has no idea what function you are in]. > > > > However, using func, here is the best I've come up with so far. It's not that > > pretty, but it's probably easier to work with than the macro version. > > > > #ifdef RTE_LIBRTE_ETHDEV_DEBUG > > -#define RTE_PMD_DEBUG_TRACE(fmt, args...) \ > > - RTE_LOG(ERR, PMD, "%s: " fmt, __func__, ## args) > > +#define RTE_PMD_DEBUG_TRACE(...) \ > > + rte_pmd_debug_trace(__func__, __VA_ARGS__) > > + > > +static inline void > > +rte_pmd_debug_trace(const char *func_name, const char *fmt, ...) > > +{ > > + static __thread char buffer[128]; > > + char *out_buf = buffer; > > + unsigned count; > > + va_list ap; > > + > > + count = snprintf(buffer, sizeof(buffer), "%s: %s", func_name, fmt); > > + if (count >= sizeof(buffer)) { // truncated output > > + char *new_buf = malloc(count + 1); > > + if (new_buf == NULL) // no memory, just print 128 chars > > + goto print_buffer; > > + snprintf(new_buf, count + 1, "%s: %s", func_name, fmt); > > + va_start(ap, fmt); > > + rte_vlog(RTE_LOG_ERR, RTE_LOGTYPE_PMD, buffer, ap); > > + va_end(ap); > > + free(new_buf); > > + return; > > + } > > + > > +print_buffer: > > + va_start(ap, fmt); > > + rte_vlog(RTE_LOG_ERR, RTE_LOGTYPE_PMD, out_buf, ap); > > + va_end(ap); > > +} > > #else > > #define RTE_PMD_DEBUG_TRACE(fmt, args...) > > #endif > > > > Comments or improvements? Such a function shouldn't malloc() anything. The entire line should fit on the stack (crashing is fine if it does not, then it's probably a bug). We did something in two passes along these lines in mlx5_defs.h (not pretty but quite useful): /* Allocate a buffer on the stack and fill it with a printf format string. */ #define MKSTR(name, ...) \ char name[snprintf(NULL, 0, __VA_ARGS__) + 1]; \ \ snprintf(name, sizeof(name), __VA_ARGS__) Untested but I guess modifying that function accordingly would look like: static inline void rte_pmd_debug_trace(const char *func_name, const char *fmt, ...) { va_list ap; va_start(ap, fmt); static __thread char buffer[vsnprintf(NULL, 0, fmt, ap)]; va_end(ap); va_start(ap, fmt); vsnprintf(buffer, sizeof(buffer), fmt, ap); va_end(ap); rte_log(RTE_LOG_ERR, RTE_LOGTYPE_PMD, "%s: %s", func_name, buffer); } > And here's the version if we are happy to have file and line number instead of > function name. I think this might be the best option. > > /Bruce > > #ifdef RTE_LIBRTE_ETHDEV_DEBUG > -#define RTE_PMD_DEBUG_TRACE(fmt, args...) \ > - RTE_LOG(ERR, PMD, "%s: " fmt, __func__, ## args) > +#define RTE_PMD_DEBUG_TRACE(...) \ > + RTE_LOG(ERR, PMD, __FILE__", " RTE_STR(__LINE__) ": " __VA_ARGS__) > #else > -#define RTE_PMD_DEBUG_TRACE(fmt, args...) > +#define RTE_PMD_DEBUG_TRACE(...) > #endif Much cleaner indeed, however __func__ might be useful when comparing log outputs from different source code versions. I think we should keep it. -- Adrien Mazarguil 6WIND