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Message-ID: <1403220789.2753.32.camel@joe-AO725> Date: Thu, 19 Jun 2014 16:33:09 -0700 From: Joe Perches <joe@...ches.com> To: Pranith Kumar <bobby.prani@...il.com> Cc: paulmck@...ux.vnet.ibm.com, LKML <linux-kernel@...r.kernel.org>, romanov.arya@...il.com, Josh Triplett <josh@...htriplett.org> Subject: Re: [RFC PATCH] use snprintf instead of sprintf in rcu_torture_printk On Thu, 2014-06-19 at 19:24 -0400, Pranith Kumar wrote: > (dropping some CCs) > > On 06/19/2014 05:00 PM, Paul E. McKenney wrote: > > On Wed, Jun 18, 2014 at 12:49:42PM -0700, Joe Perches wrote: > >> > >> I believe the function doesn't work well. > >> > >> static void > >> rcu_torture_stats_print(void) > >> { > >> int size = nr_cpu_ids * 200 + 8192; > >> char *buf; > >> > >> buf = kmalloc(size, GFP_KERNEL); > >> if (!buf) { > >> pr_err("rcu-torture: Out of memory, need: %d\n", size); > >> return; > >> } > >> rcu_torture_printk(buf); > >> pr_alert("%s", buf); > >> kfree(buf); > >> } > >> > >> rcu_torture_printk simply fills buf > >> > >> btw: I believe the arguments should pass size and > >> rcu_torture_printk should use snprintf/size > >> > >> but all printks are limited to a maximum of 1024 > >> bytes so the large allocation is senseless and > >> would even if it worked, would likely need to be > >> vmalloc/vfree > > > > Fair point! > > > > Pranith, Romanov, if you would like part of RCU that is less touchy > > about random hacking, this would be a good place to start. Scripts in > > tools/testing/selftests/rcutorture/bin do care about some of the format, > > but the variable-length portion generated by cur_ops->stats() is as far > > as I know only parsed by human eyes. > > > > Here is a first run of the change. Please let me know if I am totally off. RFC. :) > > Three things on Todo list: > > * We need to check that we are using less than the allocated size of the buffer (used > size). (we are allocating a big buffer, so not sure if necessary) > * Need to check with the scripts if they are working. > * I used a loop for pr_alert(). I am not sure this is right, there should be a better way for printing large buffers > > If the overall structure is ok I will go ahead and check how the scripts are handling these changes. [] > diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c [] > @@ -1130,17 +1134,23 @@ rcu_torture_printk(char *page) > static void > rcu_torture_stats_print(void) > { [] > + /* printk can print only print LOG_LINE_MAX chars at a time */ > + while (used > 0) { > + size_pr = pr_alert("%s", buf); > + used -= size_pr; > + buf += size_pr; > + } > + vfree(buf); > } You can't increment buf then vfree it. Try a char *tmpbuf = buf, and increment it. I suggest you check by strcspn(tmpbuf, "\n") save the byte after, replace it with 0, print, replace the 0 with saved byte, and loop until end of buffer. -- 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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