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Corinna Vinschen 717c36c0a4 Cygwin: fork: fix a potential hang in fork 
while debugging a problem introduced in commit
63b503916d ("Cygwin: tls_pathbuf: Use Windows heap")
a hang in fork was encountered using the original implementation
of tls_pathbuf:

Using tmp_pathbuf inside the code block guarded by __malloc_trylock
may call malloc from tmp_pathbuf::w_get and thus trying to lock an
exclusive SRW lock recursively, which results in a deadlock.

Allocate a small SECURITY_ATTRIBUTES block on the stack rather than
allocating a 64K tmp_pathbuf.  This avoids the potential malloc call.

Drop the __malloc_trylock call entirely.  There must not be a malloc
call inside the frok::parent block guarded by __malloc_lock, and
just trying to lock is too dangerous inside fork while other threads
might actually chage the content of the heap.  Additionally, add a
comment frowning on malloc usage inside tis code block.

Fixes: 44a79a6eca ("Cygwin: convert malloc lock to SRWLOCK")
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
 		2022-08-29 12:25:24 +02:00
..
CVSChangeLogs.old
…
cygserver Revert "sys/types.h: Don't include sys/_stdint.h" 2022-05-04 15:08:44 +02:00
cygwin Cygwin: fork: fix a potential hang in fork 2022-08-29 12:25:24 +02:00
doc Update FAQs which are out of date on the details of setup UI 2022-07-12 13:58:59 +01:00
testsuite Cygwin: remove some 32-bit only path conversion functions 2022-05-29 17:45:52 -04:00
utils Cygwin: profiler: Fix linking when building with -DDEBUGGING 2022-08-20 21:14:57 +02:00
CONTRIBUTORS Cygwin: Add Ben Wijen to list of contributors 2021-01-18 12:01:19 +01:00
COPYING
…
COPYING.LIB
…
CYGWIN_LICENSE
…
Makefile.am Cygwin: Conditionally build documentation 2021-12-17 22:28:16 +00:00
Makefile.am.common Cygwin: automake: change @INCLUDES@ to @AM_CPPFLAGS@ to avoid warnings 2021-04-29 11:28:14 +02:00
README
…
acinclude.m4 Cygwin: Reorganize cygwin source dir 2022-08-05 12:02:11 +02:00
autogen.sh Cygwin: autogen.sh: Allow running from any directory 2021-05-06 10:56:20 +02:00
configure.ac Cygwin: fold common.din and x86_64.din into cygwin.din 2022-08-08 17:47:46 +02:00

README 

THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESSED OR
IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

Cygwin documentation is available on the net at https://cygwin.com
You might especially be interested in

https://cygwin.com/faq/faq.html#faq.programming.building-cygwin