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[PATCH v3 27/27] attr: reformat git_attr_set_direction() function

From
BWBrandon Williams <bmwill@google.com>
Date
Jan 28, 2017, 02:02 UTC
Message-ID
<20170128020207.179015-28-bmwill@google.com>
In-Reply-To
<20170128020207.179015-1-bmwill@google.com>

Move the 'git_attr_set_direction()' up to be closer to the variables that it modifies as well as a small formatting by renaming the variable 'new' to 'new_direction' so that it is more descriptive.

Update the comment about how 'direction' is used to read the state of the world. It should be noted that callers of 'git_attr_set_direction()' should ensure that other threads are not making calls into the attribute system until after the call to 'git_attr_set_direction()' completes. This function essentially acts as reset button for the attribute system and should be handled with care.

Signed-off-by: Brandon Williams <bmwill@google.com>
---
 attr.c | 49 ++++++++++++++++++++-----------------------------
 attr.h |  3 ++-
 2 files changed, 22 insertions(+), 30 deletions(-)
diff --git a/attr.c b/attr.c
index 62298ec2f..5493bff22 100644
--- a/attr.c
+++ b/attr.c
@@ -677,26 +677,30 @@ static struct attr_stack *read_attr_from_array(const char **list)
 }
 
 /*
- * NEEDSWORK: these two are tricky.  The callers assume there is a
- * single, system-wide global state "where we read attributes from?"
- * and when the state is flipped by calling git_attr_set_direction(),
- * attr_stack is discarded so that subsequent attr_check will lazily
- * read from the right place.  And they do not know or care who called
- * by them uses the attribute subsystem, hence have no knowledge of
- * existing git_attr_check instances or future ones that will be
- * created).
- *
- * Probably we need a thread_local that holds these two variables,
- * and a list of git_attr_check instances (which need to be maintained
- * by hooking into git_attr_check_alloc(), git_attr_check_initl(), and
- * git_attr_check_clear().  Then git_attr_set_direction() updates the
- * fields in that thread_local for these two variables, iterate over
- * all the active git_attr_check instances and discard the attr_stack
- * they hold.  Yuck, but it sounds doable.
+ * Callers into the attribute system assume there is a single, system-wide
+ * global state where attributes are read from and when the state is flipped by
+ * calling git_attr_set_direction(), the stack frames that have been
+ * constructed need to be discarded so so that subsequent calls into the
+ * attribute system will lazily read from the right place.  Since changing
+ * direction causes a global paradigm shift, it should not ever be called while
+ * another thread could potentially be calling into the attribute system.
  */
 static enum git_attr_direction direction;
 static struct index_state *use_index;
 
+void git_attr_set_direction(enum git_attr_direction new_direction,
+			    struct index_state *istate)
+{
+	if (is_bare_repository() && new_direction != GIT_ATTR_INDEX)
+		die("BUG: non-INDEX attr direction in a bare repo");
+
+	if (new_direction != direction)
+		drop_all_attr_stacks();
+
+	direction = new_direction;
+	use_index = istate;
+}
+
 static struct attr_stack *read_attr_from_file(const char *path, int macro_ok)
 {
 	FILE *fp = fopen(path, "r");
@@ -1148,19 +1152,6 @@ void git_all_attrs(const char *path, struct attr_check *check)
 	}
 }
 
-void git_attr_set_direction(enum git_attr_direction new, struct index_state *istate)
-{
-	enum git_attr_direction old = direction;
-
-	if (is_bare_repository() && new != GIT_ATTR_INDEX)
-		die("BUG: non-INDEX attr direction in a bare repo");
-
-	direction = new;
-	if (new != old)
-		drop_all_attr_stacks();
-	use_index = istate;
-}
-
 void attr_start(void)
 {
 #ifndef NO_PTHREADS
diff --git a/attr.h b/attr.h
index 6f4961fdb..48ab3e1c2 100644
--- a/attr.h
+++ b/attr.h
@@ -72,7 +72,8 @@ enum git_attr_direction {
 	GIT_ATTR_CHECKOUT,
 	GIT_ATTR_INDEX
 };
-void git_attr_set_direction(enum git_attr_direction, struct index_state *);
+void git_attr_set_direction(enum git_attr_direction new_direction,
+			    struct index_state *istate);
 
 extern void attr_start(void);
 

-- 
2.11.0.483.g087da7b7c-goog
Previous: Brandon WilliamsNext: Brandon Williams
Message 107 of 111 in “Revamp the attribute system; another round”
  1. 00/27 Revamp the attribute system; another roundBrandon Williams, Jan 12, 2017
  2. 20/27 attr: change validity check for attribute names to use positive logicBrandon Williams, Jan 12, 2017
  3. 19/27 attr: pass struct attr_check to collect_some_attrsBrandon Williams, Jan 12, 2017
  4. 18/27 attr: retire git_check_attrs() APIBrandon Williams, Jan 12, 2017
  5. 17/27 attr: convert git_check_attrs() callers to use the new APIBrandon Williams, Jan 12, 2017
  6. 15/27 attr: (re)introduce git_check_attr() and struct attr_checkBrandon Williams, Jan 12, 2017
  7. 16/27 attr: convert git_all_attrs() to use "struct attr_check"Brandon Williams, Jan 12, 2017
  8. 23/27 attr: remove maybe-real, maybe-macro from git_attrBrandon Williams, Jan 12, 2017
  9. 24/27 attr: tighten const correctness with git_attr and match_attrBrandon Williams, Jan 12, 2017
  10. 21/27 attr: use hashmap for attribute dictionaryBrandon Williams, Jan 12, 2017
  11. Stefan BellerJan 18, 2017
  12. Brandon WilliamsJan 18, 2017
  13. 25/27 attr: store attribute stacks in hashmapBrandon Williams, Jan 12, 2017
  14. Junio C HamanoJan 13, 2017
  15. Brandon WilliamsJan 18, 2017
  16. Brandon WilliamsJan 23, 2017
  17. Stefan BellerJan 18, 2017
  18. Brandon WilliamsJan 18, 2017
  19. Stefan BellerJan 18, 2017
  20. 22/27 attr: eliminate global check_all_attr arrayBrandon Williams, Jan 12, 2017
  21. 27/27 attr: reformat git_attr_set_direction() functionBrandon Williams, Jan 12, 2017
  22. 26/27 attr: push the bare repo check into read_attr()Brandon Williams, Jan 12, 2017
  23. 13/27 attr.c: outline the future plans by heavily commentingBrandon Williams, Jan 12, 2017
  24. 12/27 Documentation: fix a typoBrandon Williams, Jan 12, 2017
  25. 01/27 commit.c: use strchrnul() to scan for one lineBrandon Williams, Jan 12, 2017
  26. 02/27 attr.c: use strchrnul() to scan for one lineBrandon Williams, Jan 12, 2017
  27. 11/27 attr.c: add push_stack() helperBrandon Williams, Jan 12, 2017
  28. 08/27 attr.c: tighten constness around "git_attr" structureBrandon Williams, Jan 12, 2017
  29. 14/27 attr: rename function and struct related to checking attributesBrandon Williams, Jan 12, 2017
  30. 06/27 attr.c: mark where #if DEBUG ends more clearlyBrandon Williams, Jan 12, 2017
  31. 07/27 attr.c: simplify macroexpand_one()Brandon Williams, Jan 12, 2017
  32. 10/27 attr: support quoting pathname patterns in C styleBrandon Williams, Jan 12, 2017
  33. 09/27 attr.c: plug small leak in parse_attr_line()Brandon Williams, Jan 12, 2017
  34. 04/27 attr.c: explain the lack of attr-name syntax check in parse_attr()Brandon Williams, Jan 12, 2017
  35. 05/27 attr.c: complete a sentence in a commentBrandon Williams, Jan 12, 2017
  36. 03/27 attr.c: update a stale comment on "struct match_attr"Brandon Williams, Jan 12, 2017
  37. Junio C HamanoJan 15, 2017
  38. Jeff KingJan 16, 2017
  39. 00/27 Revamp the attribute system; another roundBrandon Williams, Jan 23, 2017
  40. 01/27 commit.c: use strchrnul() to scan for one lineBrandon Williams, Jan 23, 2017
  41. 02/27 attr.c: use strchrnul() to scan for one lineBrandon Williams, Jan 23, 2017
  42. 03/27 attr.c: update a stale comment on "struct match_attr"Brandon Williams, Jan 23, 2017
  43. 04/27 attr.c: explain the lack of attr-name syntax check in parse_attr()Brandon Williams, Jan 23, 2017
  44. 05/27 attr.c: complete a sentence in a commentBrandon Williams, Jan 23, 2017
  45. 07/27 attr.c: simplify macroexpand_one()Brandon Williams, Jan 23, 2017
  46. 10/27 attr: support quoting pathname patterns in C styleBrandon Williams, Jan 23, 2017
  47. 12/27 Documentation: fix a typoBrandon Williams, Jan 23, 2017
  48. 13/27 attr.c: outline the future plans by heavily commentingBrandon Williams, Jan 23, 2017
  49. 09/27 attr.c: plug small leak in parse_attr_line()Brandon Williams, Jan 23, 2017
  50. 11/27 attr.c: add push_stack() helperBrandon Williams, Jan 23, 2017
  51. 14/27 attr: rename function and struct related to checking attributesBrandon Williams, Jan 23, 2017
  52. 20/27 attr: change validity check for attribute names to use positive logicBrandon Williams, Jan 23, 2017
  53. 21/27 attr: use hashmap for attribute dictionaryBrandon Williams, Jan 23, 2017
  54. 22/27 attr: eliminate global check_all_attr arrayBrandon Williams, Jan 23, 2017
  55. Junio C HamanoJan 23, 2017
  56. 16/27 attr: convert git_all_attrs() to use "struct attr_check"Brandon Williams, Jan 23, 2017
  57. 23/27 attr: remove maybe-real, maybe-macro from git_attrBrandon Williams, Jan 23, 2017
  58. 24/27 attr: tighten const correctness with git_attr and match_attrBrandon Williams, Jan 23, 2017
  59. 17/27 attr: convert git_check_attrs() callers to use the new APIBrandon Williams, Jan 23, 2017
  60. 18/27 attr: retire git_check_attrs() APIBrandon Williams, Jan 23, 2017
  61. 15/27 attr: (re)introduce git_check_attr() and struct attr_checkBrandon Williams, Jan 23, 2017
  62. 06/27 attr.c: mark where #if DEBUG ends more clearlyBrandon Williams, Jan 23, 2017
  63. 08/27 attr.c: tighten constness around "git_attr" structureBrandon Williams, Jan 23, 2017
  64. 19/27 attr: pass struct attr_check to collect_some_attrsBrandon Williams, Jan 23, 2017
  65. 26/27 attr: push the bare repo check into read_attr()Brandon Williams, Jan 23, 2017
  66. 27/27 attr: reformat git_attr_set_direction() functionBrandon Williams, Jan 23, 2017
  67. 25/27 attr: store attribute stack in attr_check structureBrandon Williams, Jan 23, 2017
  68. Junio C HamanoJan 23, 2017
  69. Brandon WilliamsJan 23, 2017
  70. Brandon WilliamsJan 24, 2017
  71. Junio C HamanoJan 24, 2017
  72. Brandon WilliamsJan 25, 2017
  73. Stefan BellerJan 25, 2017
  74. Junio C HamanoJan 25, 2017
  75. Brandon WilliamsJan 25, 2017
  76. Brandon WilliamsJan 25, 2017
  77. 00/27 Revamp the attribute system; another roundBrandon Williams, Jan 28, 2017
  78. 01/27 commit.c: use strchrnul() to scan for one lineBrandon Williams, Jan 28, 2017
  79. 02/27 attr.c: use strchrnul() to scan for one lineBrandon Williams, Jan 28, 2017
  80. 05/27 attr.c: complete a sentence in a commentBrandon Williams, Jan 28, 2017
  81. 03/27 attr.c: update a stale comment on "struct match_attr"Brandon Williams, Jan 28, 2017
  82. 07/27 attr.c: simplify macroexpand_one()Brandon Williams, Jan 28, 2017
  83. 06/27 attr.c: mark where #if DEBUG ends more clearlyBrandon Williams, Jan 28, 2017
  84. 08/27 attr.c: tighten constness around "git_attr" structureBrandon Williams, Jan 28, 2017
  85. 04/27 attr.c: explain the lack of attr-name syntax check in parse_attr()Brandon Williams, Jan 28, 2017
  86. 09/27 attr.c: plug small leak in parse_attr_line()Brandon Williams, Jan 28, 2017
  87. 10/27 attr: support quoting pathname patterns in C styleBrandon Williams, Jan 28, 2017
  88. 11/27 attr.c: add push_stack() helperBrandon Williams, Jan 28, 2017
  89. 12/27 Documentation: fix a typoBrandon Williams, Jan 28, 2017
  90. 15/27 attr: (re)introduce git_check_attr() and struct attr_checkBrandon Williams, Jan 28, 2017
  91. 15/27 attr: (re)introduce git_check_attr() and struct attr_checkBrandon Williams, Jan 30, 2017
  92. 13/27 attr.c: outline the future plans by heavily commentingBrandon Williams, Jan 28, 2017
  93. 16/27 attr: convert git_all_attrs() to use "struct attr_check"Brandon Williams, Jan 28, 2017
  94. Stefan BellerJan 28, 2017
  95. Brandon WilliamsJan 29, 2017
  96. 16/27 attr: convert git_all_attrs() to use "struct attr_check"Brandon Williams, Jan 30, 2017
  97. 14/27 attr: rename function and struct related to checking attributesBrandon Williams, Jan 28, 2017
  98. 18/27 attr: retire git_check_attrs() APIBrandon Williams, Jan 28, 2017
  99. 19/27 attr: pass struct attr_check to collect_some_attrsBrandon Williams, Jan 28, 2017
  100. 17/27 attr: convert git_check_attrs() callers to use the new APIBrandon Williams, Jan 28, 2017
  101. 22/27 attr: eliminate global check_all_attr arrayBrandon Williams, Jan 28, 2017
  102. 21/27 attr: use hashmap for attribute dictionaryBrandon Williams, Jan 28, 2017
  103. 26/27 attr: push the bare repo check into read_attr()Brandon Williams, Jan 28, 2017
  104. 25/27 attr: store attribute stack in attr_check structureBrandon Williams, Jan 28, 2017
  105. 20/27 attr: change validity check for attribute names to use positive logicBrandon Williams, Jan 28, 2017
  106. 24/27 attr: tighten const correctness with git_attr and match_attrBrandon Williams, Jan 28, 2017
  107. 27/27 attr: reformat git_attr_set_direction() functionBrandon Williams, Jan 28, 2017
  108. 23/27 attr: remove maybe-real, maybe-macro from git_attrBrandon Williams, Jan 28, 2017
  109. Junio C HamanoFeb 2, 2017
  110. Brandon WilliamsFeb 9, 2017
  111. Junio C HamanoFeb 9, 2017

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