user/sven/git.git/grep.c, branch v2.26.0-rc2

grep: replace grep_read_mutex by internal obj read lock

2020-01-17T21:52:14Z

git-grep uses 'grep_read_mutex' to protect its calls to object reading operations. But these have their own internal lock now, which ensures a better performance (allowing parallel access to more regions). So, let's remove the former and, instead, activate the latter with enable_obj_read_lock(). Sections that are currently protected by 'grep_read_mutex' but are not internally protected by the object reading lock should be surrounded by obj_read_lock() and obj_read_unlock(). These guarantee mutual exclusion with object reading operations, keeping the current behavior and avoiding race conditions. Namely, these places are: In grep.c: - fill_textconv() at fill_textconv_grep(). - userdiff_get_textconv() at grep_source_1(). In builtin/grep.c: - parse_object_or_die() and the submodule functions at grep_submodule(). - deref_tag() and gitmodules_config_oid() at grep_objects(). If these functions become thread-safe, in the future, we might remove the locking and probably get some speedup. Note that some of the submodule functions will already be thread-safe (or close to being thread-safe) with the internal object reading lock. However, as some of them will require additional modifications to be removed from the critical section, this will be done in its own patch. Signed-off-by: Matheus Tavares Signed-off-by: Junio C Hamano

grep: fix race conditions on userdiff calls

2020-01-17T21:52:14Z

git-grep uses an internal grep_read_mutex to protect object reading operations. Similarly, there's a grep_attr_mutex to protect calls to the gitattributes machinery. However, two of the three functions protected by the last mutex may also perform object reading, as seen below: - userdiff_get_textconv() > notes_cache_init() > notes_cache_match_validity() > lookup_commit_reference_gently() > parse_object() > repo_has_object_file() > repo_has_object_file_with_flags() > oid_object_info_extended() - userdiff_find_by_path() > git_check_attr() > collect_some_attrs() > prepare_attr_stack() > read_attr() > read_attr_from_index() > read_blob_data_from_index() > read_object_file() As these calls are not protected by grep_read_mutex, there might be race conditions with other threads performing object reading (e.g. threads calling fill_textconv() at grep.c:fill_textconv_grep()). To prevent that, let's make sure to acquire the lock before both of these calls. Note: this patch might slow down the threaded grep in worktree, for the sake of thread-safeness. However, in the following patches, we should regain performance by replacing grep_read_mutex for an internal object reading lock and allowing parallel inflation during object reading. Signed-off-by: Matheus Tavares Signed-off-by: Junio C Hamano

grep: don't return an expression from pcre2_free()

2019-11-30T22:06:58Z

Previously, the void pcre2_free() function in grep.c returned free(). While free() itself is void, afaict it's still an expression as per section A.2.3, subsection 6.8.6 (jump-statement) in both C99 [1] and C11 [2]: > return expression Section 6.8.6.4 in C99 [1] and C11 [2] says that: > A return statement with an expression shall not appear in a function > whose return type is void. The consequence of the old behavior was that developer builds with pedantic errors enabled broke Git if PCRE2 was enabled and a smart-enough compiler to detect these errors was used. This commit fixes pedantic builds of Git that enables --with-libpcre. [1] http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1256.pdf [2] http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1548.pdf Signed-off-by: Hans Jerry Illikainen Signed-off-by: Junio C Hamano

Merge branch 'cb/pcre2-chartables-leakfix'

2019-10-23T05:43:11Z

Leakfix. * cb/pcre2-chartables-leakfix: grep: avoid leak of chartables in PCRE2 grep: make PCRE2 aware of custom allocator grep: make PCRE1 aware of custom allocator

grep: avoid leak of chartables in PCRE2

2019-10-18T01:33:18Z

94da9193a6 ("grep: add support for PCRE v2", 2017-06-01) introduced a small memory leak visible with valgrind in t7813. Complete the creation of a PCRE2 specific variable that was missing from the original change and free the generated table just like it is done for PCRE1. Signed-off-by: Carlo Marcelo Arenas Belón Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano

grep: make PCRE2 aware of custom allocator

2019-10-18T01:33:18Z

94da9193a6 (grep: add support for PCRE v2, 2017-06-01) didn't include a way to override the system allocator, and so it is incompatible with custom allocators (e.g. nedmalloc). This problem became obvious when we tried to plug a memory leak by `free()`ing a data structure allocated by PCRE2, triggering a segfault in Windows (where we use nedmalloc by default). PCRE2 requires the use of a general context to override the allocator and therefore, there is a lot more code needed than in PCRE1, including a couple of wrapper functions. Extend the grep API with a "destructor" that could be called to cleanup any objects that were created and used globally. Update `builtin/grep.c` to use that new API, but any other future users should make sure to have matching `grep_init()`/`grep_destroy()` calls if they are using the pattern matching functionality. Move some of the logic that was before done per thread (in the workers) into an earlier phase to avoid degrading performance, but as the use of PCRE2 with custom allocators is better understood it is expected more of its functions will be instructed to use the custom allocator as well as was done in the original code[1] this work was based on. [1] https://public-inbox.org/git/3397e6797f872aedd18c6d795f4976e1c579514b.1565005867.git.gitgitgadget@gmail.com/ Reported-by: Johannes Schindelin Signed-off-by: Carlo Marcelo Arenas Belón Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano

grep: make PCRE1 aware of custom allocator

2019-10-18T01:33:16Z

63e7e9d8b6 ("git-grep: Learn PCRE", 2011-05-09) didn't include a way to override the system alocator, and so it is incompatible with USE_NED_ALLOCATOR as reported by Dscho[1] (in similar code from PCRE2) Note that nedmalloc, as well as other custom allocators like jemalloc and mi-malloc, can be configured at runtime (via `LD_PRELOAD`), therefore we cannot know at compile time whether a custom allocator is used or not. Make the minimum change possible to ensure this combination is supported by extending `grep_init()` to set the PCRE1 specific functions to Git's idea of `malloc()` and `free()` and therefore making sure all allocations are done inside PCRE1 with the same allocator than the rest of Git. This change has negligible performance impact: PCRE needs to allocate memory once per program run for the character table and for each pattern compilation. These are both rare events compared to matching patterns against lines. Actual measurements[2] show that the impact is lost in the noise. [1] https://public-inbox.org/git/pull.306.git.gitgitgadget@gmail.com [2] https://public-inbox.org/git/7f42007f-911b-c570-17f6-1c6af0429586@web.de Signed-off-by: Carlo Marcelo Arenas Belón Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano

Merge branch 'cb/pcre1-cleanup'

2019-10-11T05:24:47Z

PCRE fixes. * cb/pcre1-cleanup: grep: refactor and simplify PCRE1 support grep: make sure NO_LIBPCRE1_JIT disable JIT in PCRE1

Merge branch 'ab/pcre-jit-fixes'

2019-10-11T05:24:47Z

A few simplification and bugfixes to PCRE interface. * ab/pcre-jit-fixes: grep: under --debug, show whether PCRE JIT is enabled grep: do not enter PCRE2_UTF mode on fixed matching grep: stess test PCRE v2 on invalid UTF-8 data grep: create a "is_fixed" member in "grep_pat" grep: consistently use "p->fixed" in compile_regexp() grep: stop using a custom JIT stack with PCRE v1 grep: stop "using" a custom JIT stack with PCRE v2 grep: remove overly paranoid BUG(...) code grep: use PCRE v2 for optimized fixed-string search grep: remove the kwset optimization grep: drop support for \0 in --fixed-strings grep: make the behavior for NUL-byte in patterns sane grep tests: move binary pattern tests into their own file grep tests: move "grep binary" alongside the rest grep: inline the return value of a function call used only once t4210: skip more command-line encoding tests on MinGW grep: don't use PCRE2?_UTF8 with "log --encoding=" log tests: test regex backends in "--encode=" tests

Merge branch 'cb/skip-utf8-check-with-pcre1'

2019-10-06T03:25:17Z

Make sure the grep machinery does not abort when seeing a payload that is not UTF-8 even when JIT is not in use with PCRE1. * cb/skip-utf8-check-with-pcre1: grep: skip UTF8 checks explicitly