Mercurial > hg
view mercurial/mpatch.c @ 29847:9a9629b9416c stable
bundle2: fail faster when interrupted
Before this patch, bundle2 application attempted to consume remaining
bundle2 part data when the process is interrupted (SIGINT) or when
sys.exit is called (translated into a SystemExit exception). This
meant that if one of these occurred when applying a say 1 GB
changegroup bundle2 part being downloaded over a network, it may take
Mercurial *several minutes* to terminate after a SIGINT because the
process is waiting on the network to stream megabytes of data. This is
not a great user experience and a regression from bundle1. Furthermore,
many process supervisors tend to only give processes a finite amount of
time to exit after delivering SIGINT: if processes take too long to
self-terminate, a SIGKILL is issued and Mercurial has no opportunity to
clean up. This would mean orphaned locks and transactions. Not good.
This patch changes the bundle2 application behavior to fail faster
when an interrupt or system exit is requested. It does so by not
catching BaseException (which includes KeyboardInterrupt and
SystemExit) and by explicitly checking for these conditions in
yet another handler which would also seek to the end of the current
bundle2 part on failure.
The end result of this patch is that SIGINT is now reacted to
significantly faster: the active transaction is rolled back
immediately without waiting for incoming bundle2 data to be consumed.
This restores the pre-bundle2 behavior and makes Mercurial treat
signals with the urgency they deserve.
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Thu, 25 Aug 2016 19:53:14 -0700 |
parents | 284d742e5611 |
children | e9a0bcc9314d |
line wrap: on
line source
/* mpatch.c - efficient binary patching for Mercurial This implements a patch algorithm that's O(m + nlog n) where m is the size of the output and n is the number of patches. Given a list of binary patches, it unpacks each into a hunk list, then combines the hunk lists with a treewise recursion to form a single hunk list. This hunk list is then applied to the original text. The text (or binary) fragments are copied directly from their source Python objects into a preallocated output string to avoid the allocation of intermediate Python objects. Working memory is about 2x the total number of hunks. Copyright 2005, 2006 Matt Mackall <mpm@selenic.com> This software may be used and distributed according to the terms of the GNU General Public License, incorporated herein by reference. */ #define PY_SSIZE_T_CLEAN #include <Python.h> #include <stdlib.h> #include <string.h> #include "util.h" #include "bitmanipulation.h" static char mpatch_doc[] = "Efficient binary patching."; static PyObject *mpatch_Error; struct frag { int start, end, len; const char *data; }; struct flist { struct frag *base, *head, *tail; }; static struct flist *lalloc(Py_ssize_t size) { struct flist *a = NULL; if (size < 1) size = 1; a = (struct flist *)malloc(sizeof(struct flist)); if (a) { a->base = (struct frag *)malloc(sizeof(struct frag) * size); if (a->base) { a->head = a->tail = a->base; return a; } free(a); a = NULL; } if (!PyErr_Occurred()) PyErr_NoMemory(); return NULL; } static void lfree(struct flist *a) { if (a) { free(a->base); free(a); } } static Py_ssize_t lsize(struct flist *a) { return a->tail - a->head; } /* move hunks in source that are less cut to dest, compensating for changes in offset. the last hunk may be split if necessary. */ static int gather(struct flist *dest, struct flist *src, int cut, int offset) { struct frag *d = dest->tail, *s = src->head; int postend, c, l; while (s != src->tail) { if (s->start + offset >= cut) break; /* we've gone far enough */ postend = offset + s->start + s->len; if (postend <= cut) { /* save this hunk */ offset += s->start + s->len - s->end; *d++ = *s++; } else { /* break up this hunk */ c = cut - offset; if (s->end < c) c = s->end; l = cut - offset - s->start; if (s->len < l) l = s->len; offset += s->start + l - c; d->start = s->start; d->end = c; d->len = l; d->data = s->data; d++; s->start = c; s->len = s->len - l; s->data = s->data + l; break; } } dest->tail = d; src->head = s; return offset; } /* like gather, but with no output list */ static int discard(struct flist *src, int cut, int offset) { struct frag *s = src->head; int postend, c, l; while (s != src->tail) { if (s->start + offset >= cut) break; postend = offset + s->start + s->len; if (postend <= cut) { offset += s->start + s->len - s->end; s++; } else { c = cut - offset; if (s->end < c) c = s->end; l = cut - offset - s->start; if (s->len < l) l = s->len; offset += s->start + l - c; s->start = c; s->len = s->len - l; s->data = s->data + l; break; } } src->head = s; return offset; } /* combine hunk lists a and b, while adjusting b for offset changes in a/ this deletes a and b and returns the resultant list. */ static struct flist *combine(struct flist *a, struct flist *b) { struct flist *c = NULL; struct frag *bh, *ct; int offset = 0, post; if (a && b) c = lalloc((lsize(a) + lsize(b)) * 2); if (c) { for (bh = b->head; bh != b->tail; bh++) { /* save old hunks */ offset = gather(c, a, bh->start, offset); /* discard replaced hunks */ post = discard(a, bh->end, offset); /* insert new hunk */ ct = c->tail; ct->start = bh->start - offset; ct->end = bh->end - post; ct->len = bh->len; ct->data = bh->data; c->tail++; offset = post; } /* hold on to tail from a */ memcpy(c->tail, a->head, sizeof(struct frag) * lsize(a)); c->tail += lsize(a); } lfree(a); lfree(b); return c; } /* decode a binary patch into a hunk list */ static struct flist *decode(const char *bin, Py_ssize_t len) { struct flist *l; struct frag *lt; int pos = 0; /* assume worst case size, we won't have many of these lists */ l = lalloc(len / 12 + 1); if (!l) return NULL; lt = l->tail; while (pos >= 0 && pos < len) { lt->start = getbe32(bin + pos); lt->end = getbe32(bin + pos + 4); lt->len = getbe32(bin + pos + 8); lt->data = bin + pos + 12; pos += 12 + lt->len; if (lt->start > lt->end || lt->len < 0) break; /* sanity check */ lt++; } if (pos != len) { if (!PyErr_Occurred()) PyErr_SetString(mpatch_Error, "patch cannot be decoded"); lfree(l); return NULL; } l->tail = lt; return l; } /* calculate the size of resultant text */ static Py_ssize_t calcsize(Py_ssize_t len, struct flist *l) { Py_ssize_t outlen = 0, last = 0; struct frag *f = l->head; while (f != l->tail) { if (f->start < last || f->end > len) { if (!PyErr_Occurred()) PyErr_SetString(mpatch_Error, "invalid patch"); return -1; } outlen += f->start - last; last = f->end; outlen += f->len; f++; } outlen += len - last; return outlen; } static int apply(char *buf, const char *orig, Py_ssize_t len, struct flist *l) { struct frag *f = l->head; int last = 0; char *p = buf; while (f != l->tail) { if (f->start < last || f->end > len) { if (!PyErr_Occurred()) PyErr_SetString(mpatch_Error, "invalid patch"); return 0; } memcpy(p, orig + last, f->start - last); p += f->start - last; memcpy(p, f->data, f->len); last = f->end; p += f->len; f++; } memcpy(p, orig + last, len - last); return 1; } /* recursively generate a patch of all bins between start and end */ static struct flist *fold(PyObject *bins, Py_ssize_t start, Py_ssize_t end) { Py_ssize_t len, blen; const char *buffer; if (start + 1 == end) { /* trivial case, output a decoded list */ PyObject *tmp = PyList_GetItem(bins, start); if (!tmp) return NULL; if (PyObject_AsCharBuffer(tmp, &buffer, &blen)) return NULL; return decode(buffer, blen); } /* divide and conquer, memory management is elsewhere */ len = (end - start) / 2; return combine(fold(bins, start, start + len), fold(bins, start + len, end)); } static PyObject * patches(PyObject *self, PyObject *args) { PyObject *text, *bins, *result; struct flist *patch; const char *in; char *out; Py_ssize_t len, outlen, inlen; if (!PyArg_ParseTuple(args, "OO:mpatch", &text, &bins)) return NULL; len = PyList_Size(bins); if (!len) { /* nothing to do */ Py_INCREF(text); return text; } if (PyObject_AsCharBuffer(text, &in, &inlen)) return NULL; patch = fold(bins, 0, len); if (!patch) return NULL; outlen = calcsize(inlen, patch); if (outlen < 0) { result = NULL; goto cleanup; } result = PyBytes_FromStringAndSize(NULL, outlen); if (!result) { result = NULL; goto cleanup; } out = PyBytes_AsString(result); if (!apply(out, in, inlen, patch)) { Py_DECREF(result); result = NULL; } cleanup: lfree(patch); return result; } /* calculate size of a patched file directly */ static PyObject * patchedsize(PyObject *self, PyObject *args) { long orig, start, end, len, outlen = 0, last = 0, pos = 0; Py_ssize_t patchlen; char *bin; if (!PyArg_ParseTuple(args, "ls#", &orig, &bin, &patchlen)) return NULL; while (pos >= 0 && pos < patchlen) { start = getbe32(bin + pos); end = getbe32(bin + pos + 4); len = getbe32(bin + pos + 8); if (start > end) break; /* sanity check */ pos += 12 + len; outlen += start - last; last = end; outlen += len; } if (pos != patchlen) { if (!PyErr_Occurred()) PyErr_SetString(mpatch_Error, "patch cannot be decoded"); return NULL; } outlen += orig - last; return Py_BuildValue("l", outlen); } static PyMethodDef methods[] = { {"patches", patches, METH_VARARGS, "apply a series of patches\n"}, {"patchedsize", patchedsize, METH_VARARGS, "calculed patched size\n"}, {NULL, NULL} }; #ifdef IS_PY3K static struct PyModuleDef mpatch_module = { PyModuleDef_HEAD_INIT, "mpatch", mpatch_doc, -1, methods }; PyMODINIT_FUNC PyInit_mpatch(void) { PyObject *m; m = PyModule_Create(&mpatch_module); if (m == NULL) return NULL; mpatch_Error = PyErr_NewException("mercurial.mpatch.mpatchError", NULL, NULL); Py_INCREF(mpatch_Error); PyModule_AddObject(m, "mpatchError", mpatch_Error); return m; } #else PyMODINIT_FUNC initmpatch(void) { Py_InitModule3("mpatch", methods, mpatch_doc); mpatch_Error = PyErr_NewException("mercurial.mpatch.mpatchError", NULL, NULL); } #endif