I see. Thank you. On Tue, Feb 16, 2016 at 5:04 AM David Gibson <[email protected]> wrote:
> On Mon, Feb 15, 2016 at 06:29:10PM +0000, Dan Good wrote: > > I thought I understood from our emails at the end of last year that a > > single "polished" commit was desirable. Is that not the same thing as > > taking several very small commits and bundling them into one? > > Often not, in practice. The ultimate goal is reviewability (both > before merging and when looking back at the commit history). But > that's often accomplished different ways depending on the situation. > In particular it tends to be different for initial commits of new code > from changes to existing code. > > For initial commits, it's generally best to elide patches which > correct false steps made during development, or really anything which > doesn't increase the total code size or complexity significantly. > That gives less commits to review, and cleaner code in them to > understand. > > For changes to existing code, however, the important thing is > understanding why the change is desirable and then that the changes > actually accomplish that goal. That tends towards small, single > purpose commits, so it's easy to see what changes belong to what goal > (explained in the commit message). > > Of course, that's a very broad rule of tumb, with plenty of exceptions > and wiggle room. > > > On Mon, Feb 15, 2016 at 5:53 AM David Gibson < > [email protected]> > > wrote: > > > > > On Wed, Feb 03, 2016 at 11:42:11PM +0000, Dan Good wrote: > > > > "messy bitser" - what does that mean? That's bad, isn't it? > > > > > > It's... mildly bad. > > > > > > By "bitser" I mean that it contains a number of changes that aren't > > > closely related to each other. In general that makes a patch more > > > difficult to review. How important that is depends on the complexity > > > of the changes and how mature the code being altered is, so it's not > > > really a big deal. > > > > > > The fact that altstack has been breaking Travis builds for a while > > > probably predisposed me to be uncharitable. > > > > > > > Can I help fix the builds? > > > > > > So, I've figured out what the problem is, patch coming shortly. > > > > > > > > > > > On Wed, Feb 3, 2016 at 4:28 PM David Gibson < > [email protected] > > > > > > > > wrote: > > > > > > > > > On Mon, Feb 01, 2016 at 02:43:16AM +0000, Dan Good wrote: > > > > > > > > > > > > * add altstack_remn, returns amount of stack remaining > > > > > > * increase mapping by 1 page to handle abutment case > > > > > > * capture rsp earlier > > > > > > * align stack to 16 bytes > > > > > > > > > > > > Signed-off-by: Dan Good <[email protected]> > > > > > > > > > > Bit of a messy bitser, but doesn't look it will make anything > > > > > worse. so go ahead and push. > > > > > > > > > > Unfortunately, altstack is breaking travis builds at the moment > (see, > > > > > e.g. https://travis-ci.org/dgibson/ccan/jobs/106661592) - but not > > > > > local builds for me which is making it difficult to debug. > > > > > > > > > > Some investigation showed that the test prog was getting a SIGBUS, > but > > > > > I didn't get further than that. > > > > > > > > > > altstack also breaks "make all" on any non-x86_64 platform > (including > > > > > 32-bit x86) which is pretty horrid. For that I think we need to > > > > > adjust the makefiles to look at rusty's new "ported" stuff from > _info. > > > > > > > > > > > > > > > > --- > > > > > > ccan/altstack/altstack.c | 17 ++++++++++++++--- > > > > > > ccan/altstack/altstack.h | 14 ++++++++++++++ > > > > > > ccan/altstack/test/run.c | 20 +++++++++++++------- > > > > > > 3 files changed, 41 insertions(+), 10 deletions(-) > > > > > > > > > > > > diff --git a/ccan/altstack/altstack.c b/ccan/altstack/altstack.c > > > > > > index 6faf38f..b71c64f 100644 > > > > > > --- a/ccan/altstack/altstack.c > > > > > > +++ b/ccan/altstack/altstack.c > > > > > > @@ -8,6 +8,7 @@ > > > > > > #include <signal.h> > > > > > > #include <stdio.h> > > > > > > #include <string.h> > > > > > > +#include <unistd.h> > > > > > > #include <sys/mman.h> > > > > > > > > > > > > static __thread char ebuf[ALTSTACK_ERR_MAXLEN]; > > > > > > @@ -37,6 +38,11 @@ static void segvjmp(int signum) > > > > > > } > > > > > > > > > > > > static __thread void *rsp_save_[2]; > > > > > > +static __thread rlim_t max_; > > > > > > + > > > > > > +rlim_t altstack_max(void) { > > > > > > + return max_; > > > > > > +} > > > > > > > > > > > > static ptrdiff_t rsp_save(unsigned i) { > > > > > > assert(i < 2); > > > > > > @@ -57,6 +63,7 @@ static __thread void *arg_, *out_; > > > > > > > > > > > > int altstack(rlim_t max, void *(*fn)(void *), void *arg, void > **out) > > > > > > { > > > > > > + long pgsz = sysconf(_SC_PAGESIZE); > > > > > > int ret = -1, undo = 0; > > > > > > char *m; > > > > > > struct rlimit rl_save; > > > > > > @@ -69,11 +76,16 @@ int altstack(rlim_t max, void *(*fn)(void *), > > > void > > > > > *arg, void **out) > > > > > > fn_ = fn; > > > > > > arg_ = arg; > > > > > > out_ = 0; > > > > > > + max_ = max; > > > > > > ebuf[elen = 0] = '\0'; > > > > > > if (out) *out = 0; > > > > > > > > > > > > + // if the first page below the mapping is in use, we get > > > max-pgsz > > > > > usable bytes > > > > > > + // add pgsz to max to guarantee at least max usable bytes > > > > > > + max += pgsz; > > > > > > + > > > > > > ok(getrlimit(RLIMIT_STACK, &rl_save), 1); > > > > > > - ok(setrlimit(RLIMIT_STACK, &(struct rlimit) { max, > > > > > rl_save.rlim_max }), 1); > > > > > > + ok(setrlimit(RLIMIT_STACK, &(struct rlimit) { max_, > > > > > rl_save.rlim_max }), 1); > > > > > > undo++; > > > > > > > > > > > > ok(m = mmap(0, max, PROT_READ|PROT_WRITE, > > > > > MAP_PRIVATE|MAP_ANONYMOUS|MAP_GROWSDOWN|MAP_NORESERVE, -1, 0), 1); > > > > > > @@ -91,8 +103,7 @@ int altstack(rlim_t max, void *(*fn)(void *), > void > > > > > *arg, void **out) > > > > > > ok(sigaction(SIGSEGV, &sa, &sa_save), 1); > > > > > > undo++; > > > > > > > > > > > > - asm volatile ("movq %%rsp, %%r10\nmov %0, > %%rsp\npush > > > > > %%r10" : : "g" (m + max) : "r10"); > > > > > > - rsp_save(0); > > > > > > + asm volatile ("movq %%rsp, %%r10\nmov %1, > %%rsp\nmov > > > > > %%rsp, %0\nsub $8, %%rsp\npush %%r10" : "=g" (rsp_save_[0]) : "g" > (m + > > > max) > > > > > : "r10"); > > > > > > out_ = fn_(arg_); > > > > > > asm volatile ("pop %rsp"); > > > > > > ret = 0; > > > > > > diff --git a/ccan/altstack/altstack.h b/ccan/altstack/altstack.h > > > > > > index 5570e7b..4445a2a 100644 > > > > > > --- a/ccan/altstack/altstack.h > > > > > > +++ b/ccan/altstack/altstack.h > > > > > > @@ -104,6 +104,20 @@ char *altstack_geterr(void); > > > > > > ptrdiff_t altstack_used(void); > > > > > > > > > > > > /** > > > > > > + * altstack_max - return usable stack size > > > > > > + * > > > > > > + * Returns: max value from altstack() call > > > > > > + */ > > > > > > +rlim_t altstack_max(void); > > > > > > + > > > > > > +/** > > > > > > + * altstack_remn - return amount of stack remaining > > > > > > + * > > > > > > + * Returns: altstack_max() minus altstack_used() > > > > > > + */ > > > > > > +#define altstack_remn() (altstack_max() - altstack_used()) > > > > > > + > > > > > > +/** > > > > > > * altstack_rsp_save - set initial rsp value > > > > > > * > > > > > > * Capture the current value of rsp for future altstack_used() > > > > > > diff --git a/ccan/altstack/test/run.c b/ccan/altstack/test/run.c > > > > > > index adc1020..d0b8d28 100644 > > > > > > --- a/ccan/altstack/test/run.c > > > > > > +++ b/ccan/altstack/test/run.c > > > > > > @@ -4,6 +4,7 @@ > > > > > > #include <setjmp.h> > > > > > > #include <signal.h> > > > > > > #include <string.h> > > > > > > +#include <unistd.h> > > > > > > #include <sys/mman.h> > > > > > > #include <ccan/tap/tap.h> > > > > > > #include <ccan/altstack/altstack.h> > > > > > > @@ -20,13 +21,13 @@ enum { > > > > > > }; > > > > > > int fail, call1, call2; > > > > > > char *m_; > > > > > > -rlim_t max_; > > > > > > +rlim_t msz_; > > > > > > #define e(x) (900+(x)) > > > > > > #define seterr(x) (errno = e(x)) > > > > > > #define setcall(x) ((call1 |= !errno ? (x) : 0), (call2 |= > errno || > > > > > out_ ? (x) : 0)) > > > > > > #define getrlimit(...) (fail&getrlimit_ ? > > > > > (seterr(getrlimit_), -1) : (setcall(getrlimit_), > > > > > getrlimit(__VA_ARGS__))) > > > > > > #define mmap(...) (fail&mmap_ ? > > > (seterr(mmap_), > > > > > (void *)-1) : (setcall(mmap_), mmap(__VA_ARGS__))) > > > > > > -#define munmap(a, b) (fail&munmap_ ? > > > > > (seterr(munmap_), -1) : (setcall(munmap_), > > > > > munmap(m_=(a), max_=(b)))) > > > > > > +#define munmap(a, b) (fail&munmap_ ? > > > > > (seterr(munmap_), -1) : (setcall(munmap_), > > > > > munmap(m_=(a), msz_=(b)))) > > > > > > #define setrlimit(...) (fail&setrlimit_ ? > > > > > (seterr(setrlimit_), -1) : (setcall(setrlimit_), > > > > > setrlimit(__VA_ARGS__))) > > > > > > #define sigaltstack(...) (fail&sigaltstack_ ? > > > > > (seterr(sigaltstack_), -1) : (setcall(sigaltstack_), > > > > > sigaltstack(__VA_ARGS__))) > > > > > > #define sigaction(...) (fail&sigaction_ ? > > > > > (seterr(sigaction_), -1) : (setcall(sigaction_), > > > > > sigaction(__VA_ARGS__))) > > > > > > @@ -58,7 +59,9 @@ static void *wrap(void *i) > > > > > > > > > > > > int main(void) > > > > > > { > > > > > > - plan_tests(16); > > > > > > + long pgsz = sysconf(_SC_PAGESIZE); > > > > > > + > > > > > > + plan_tests(17); > > > > > > > > > > > > #define chkfail(x, y, z, c1, c2) (call1 = 0, call2 = 0, errno = > 0, > > > > > ok1((fail = x) && (y) && errno == (z) && call1 == (c1) && call2 == > > > (c2))); > > > > > > #define chkok( y, z, c1, c2) (call1 = 0, call2 = 0, errno = > 0, > > > fail > > > > > = 0, ok1((y) && errno == (z) && call1 == (c1) && call2 == > (c2))); > > > > > > @@ -86,7 +89,7 @@ int main(void) > > > > > > chkfail(munmap_, altstack(8*MiB, wrap, 0, 0) == 1, > > > > > e(munmap_), > > > > > > > getrlimit_|setrlimit_|mmap_|sigaltstack_|sigaction_, > > > > > > setrlimit_|sigaltstack_|sigaction_); > > > > > > - if (fail = 0, munmap(m_, max_) == -1) > > > > > > + if (fail = 0, munmap(m_, msz_) == -1) > > > > > > err(1, "munmap"); > > > > > > > > > > > > chkok( altstack(1*MiB, wrap, (void *) > > > 1000000, 0) > > > > > == -1, EOVERFLOW, > > > > > > @@ -102,10 +105,12 @@ int main(void) > > > > > > chkfail(munmap_, altstack(1*MiB, wrap, (void *) > > > 1000000, 0) > > > > > == -1, EOVERFLOW, > > > > > > > getrlimit_|setrlimit_|mmap_|sigaltstack_|sigaction_, > > > > > > setrlimit_|sigaltstack_|sigaction_); > > > > > > - if (fail = 0, munmap(m_, max_) == -1) > > > > > > + if (fail = 0, munmap(m_, msz_) == -1) > > > > > > err(1, "munmap"); > > > > > > > > > > > > - ok1(used > 1*MiB-1*KiB && used < 1*MiB); > > > > > > + ok1(altstack_max() == 1*MiB); > > > > > > + diag("used: %lu", used); > > > > > > + ok1(used >= 1*MiB && used <= 1*MiB + pgsz); > > > > > > > > > > > > char *p; > > > > > > for(p = altstack_geterr(); *p; p++) > > > > > > @@ -128,7 +133,8 @@ int main(void) > > > > > > > getrlimit_|setrlimit_|mmap_|sigaltstack_|sigaction_, > > > > > > setrlimit_|munmap_|sigaltstack_|sigaction_); > > > > > > > > > > > > - ok1(used > 8*MiB-8*KiB && used < 8*MiB); > > > > > > + diag("used: %lu", used); > > > > > > + ok1(used >= 8*MiB && used <= 8*MiB + pgsz); > > > > > > > > > > > > used = 0; > > > > > > chkok( altstack(8*MiB, wrap, (void *) > 100000, > > > 0) > > > > > == 0, 0, > > > > > > > > > > > > > > > > > > -- > David Gibson | I'll have my music baroque, and my code > david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ > _other_ > | _way_ _around_! > http://www.ozlabs.org/~dgibson >
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