https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=5a41aa6f4d5eb12a1fc2ef084d98f63d65f5fcc3
commit 5a41aa6f4d5eb12a1fc2ef084d98f63d65f5fcc3
Author: Michael Haubenwallner <michael.haubenwall...@ssi-schaefer.com>
Date: Wed Dec 7 11:58:29 2016 +0100
forkables: Keep hardlinks disabled via shared mem.
To avoid the need for each process to check the filesystem to detect
that hardlink creation is impossible or disabled, cache this fact in
shared memory. Removing cygfork directory while in use does disable
hardlinks creation. To (re-)enable hardlinks creation, the cygfork
directory has to exist before the first cygwin process does fork.
* forkable.cc (dll_list::forkable_ntnamesize): Short cut
forkables needs to impossible when disabled via shared memory.
(dll_list::update_forkables_needs): When detecting hardlink
creation as impossible (not on NTFS) while still (we are the
first one checking) enabled via shared memory, disable the
shared memory value.
(dll_list::request_forkables): Disable the shared memory value
when hardlinks creation became disabled, that is when the
cygfork directory was removed.
* include/cygwin/version.h: Bump CYGWIN_VERSION_SHARED_DATA 6.
* shared_info.h (struct shared_info): Add member
prefer_forkable_hardlinks. Update CURR_SHARED_MAGIC.
* shared.cc (shared_info::initialize): Initialize
prefer_forkable_hardlinks to 1 (Yes).
Diff:
---
winsup/cygwin/forkable.cc | 13 +++++++++++++
winsup/cygwin/include/cygwin/version.h | 2 +-
winsup/cygwin/shared_info.h | 3 ++-
3 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/winsup/cygwin/forkable.cc b/winsup/cygwin/forkable.cc
index cc28f9f..da45643 100644
--- a/winsup/cygwin/forkable.cc
+++ b/winsup/cygwin/forkable.cc
@@ -522,6 +522,11 @@ dll::create_forkable ()
size_t
dll_list::forkable_ntnamesize (dll_type type, PCWCHAR fullntname, PCWCHAR
modname)
{
+ /* per process, this is the first forkables-method ever called */
+ if (forkables_needs == forkables_unknown &&
+ !cygwin_shared->prefer_forkable_hardlinks)
+ forkables_needs = forkables_impossible; /* short cut */
+
if (forkables_needs == forkables_impossible)
return 0;
@@ -667,6 +672,7 @@ dll_list::update_forkables_needs ()
{
debug_printf ("impossible, not on NTFS %W", fn.Buffer);
forkables_needs = forkables_impossible;
+ cygwin_shared->prefer_forkable_hardlinks = 0;
}
}
@@ -1056,6 +1062,13 @@ dll_list::request_forkables ()
set_forkables_inheritance (true);
+ if (forkables_needs == forkables_disabled)
+ {
+ /* we do not support (re-)enabling on the fly */
+ forkables_needs = forkables_impossible;
+ cygwin_shared->prefer_forkable_hardlinks = 0;
+ }
+
if (forkables_needs <= forkables_needless)
return;
diff --git a/winsup/cygwin/include/cygwin/version.h
b/winsup/cygwin/include/cygwin/version.h
index 8926d49..f7ed351 100644
--- a/winsup/cygwin/include/cygwin/version.h
+++ b/winsup/cygwin/include/cygwin/version.h
@@ -518,7 +518,7 @@ details. */
regions. It is incremented when incompatible changes are made to the shared
memory region *or* to any named shared mutexes, semaphores, etc. */
-#define CYGWIN_VERSION_SHARED_DATA 5
+#define CYGWIN_VERSION_SHARED_DATA 6
/* An identifier used in the names used to create shared objects. The full
names include the CYGWIN_VERSION_SHARED_DATA version as well as this
diff --git a/winsup/cygwin/shared_info.h b/winsup/cygwin/shared_info.h
index 1a5648b..8f0954f 100644
--- a/winsup/cygwin/shared_info.h
+++ b/winsup/cygwin/shared_info.h
@@ -33,7 +33,7 @@ public:
/* Data accessible to all tasks */
-#define CURR_SHARED_MAGIC 0x6758de88U
+#define CURR_SHARED_MAGIC 0x3a6025edU
#define USER_VERSION 1
@@ -51,6 +51,7 @@ class shared_info
mtinfo mt;
loadavginfo loadavg;
LONG pid_src;
+ char prefer_forkable_hardlinks; /* single byte access always is atomic */
void initialize ();
void init_obcaseinsensitive ();
