Pipes consist of two filps (read filp and write filp) and a shared
vnode. When the writer leaves the filp reference count drops to
zero and subsequent find_filp()s should not find the filp when a
reader looks for it and the reader gets EOF. However, the pipe()
system call tries to find two filps, marks them in use, and only
after a successful node creation on PFS, overwrites the shared
vnode with the new vnode. Consequently, this leaves a small window
where a just closed 'pipe write filp' gets reused and marked as
present, before becoming the actual new 'pipe write filp' for a new
pipe. A reader for the old pipe will think a writer is present and
wait for that writer to write something or to leave; both actions
should revive the suspended reader. This will never happen and the
reader will be stuck forever.
TTY has no way of keeping track of multiple readers for a tty minor
device. Instead, it stores a read request for the last reader only.
Consequently, the first ("overwritten") reader gets stuck on a read
request that's never going to be finished. Also, the overwriting
causes a grant mismatch in VFS when TTY returns a reply for the
second reader.
This patch is a work around for the actual problem (i.e., keeping track
of multiple readers). It checks whether there is a read operation in
progress and returns an error if it is --preventing that reader from
getting overwritten and stuck. It fixes a bug triggered by executing
'top | more' and pressing the space bar for a while (easily reproducable
in a VM, not on hardware).
When running out of worker threads to handle device replies a dead
lock resolver thread is used. However, it was only used for FS
endpoints; it is now used for "system processes" (drivers and FS
endpoints). Also, drivers were marked as system process when they
were not "forced" to map (i.e., mapping was done before endpoint was
alive).
By making m_in job local (i.e., each job has its own copy of m_in instead
of refering to the global m_in) we don't have to store and restore m_in
on every thread yield. This reduces overhead. Moreover, remove the
assumption that m_in is preserved. Do_XXX functions have to copy the
system call parameters as soon as possible and only pass those copies to
other functions.
Furthermore, this patch cleans up some code and uses better types in a lot
of places.
. file- and functionality-compatible with previous situation
(FreeBSD csu) (with a crt1.o -> crt0.o symlink in /usr/lib)
. harmonizes source with netbsd
. harmonizes linker invocation (e.g. clang) with netbsd
. helpful to get some arm code in there for the arm port project
use the user-supplied point to lookup which region to perform brk() on,
and if it's a reasonable one, do it, no matter what vm's notion of the
heap region is.
This Shared Folders File System library (libsffs) now contains all the
file system logic originally in HGFS. The actual HGFS server code is
now a stub that passes on all the work to libsffs. The libhgfs library
is changed accordingly.
. remove some call cycles by low-level functions invoking printf(); e.g.
send_sig() gets a return value that the caller should check
. reason: very-early-phase printf() would trigger a printf() causing
infinite recursion -> GPF
. move serial initialization a little earlier so DEBUG_EXTRA works for
serial earlier (e.g. its first instance, for "cstart")
. closes tracker item 583:
System Fails to Complete Startup with Verbose 2 and 3 Boot Parameters,
reported by Stephen Hatton / pikpik.
You might have to update the compiler-rt package! See UPDATING.
. the purpose of this -L was solely to find compiler-rt, which contains
runtime support code for clang-compiled binaries
. this also makes all other packaged libraries visible, however
. it is cleaner to isolate the base system from packages, and so
compiler-rt puts itself in /usr/pkg/compiler-rt/lib/ too, which the
base system henceforth uses exclusively
. e.g. this solves a link failure when libfetch is installed as a
package
. the new compiler-rt package also puts itself in /usr/pkg/lib for 'old'
systems; that is harmless. The benefit of 'new' systems is that the other
packages are hidden.
