many locations: Change occurences of open() followed by file_detach() to file_open(). Change most non-controversion calls to open() to nx_open().
fs/inode/fs_fileopen.c: Flesh out file_open() with some interim, placeholder logic.
fs/inode/fs_fileopen.c: Add a framework for a file_open() implementation (no real logic in place yet).
fs/vfs/fs_open.c: Add nx_open() which is the same as open() except that it does not create a cancellation point nor does it modify the errno variable.
sched/wqueue/kwork_notifier.c: Redesign some data structures. struct works_s must appear at the beginning of the notifier entry structure. That is because it contains the work queue indices. This solves a harfault issue.
net/tcp/tcp_netpoll.c: tcp_iob_work() needs to free the allocated argument when it is finished.
net/tcp/tcp_send_buffered.c: Extend psock_tcp_cansend() so that it also requires that at least on IOB is also avaialble.
mm/iob: iob_navail() was returning the number of free IOB chain queue entries, not the number of free IOBs. Completely misnamed.
net/tcp/tcp_netpoll.c: Add logic to receive notifications when IOBs are freed (Needs CONFIG_NET_TCP_WRITE_BUFFERS and CONFIG_IOB_NOTIFIER). At present, does nothing because the logic in in psock_tcp_cansend() does not check for the availability of IOBs. That will change.
TASK A TASK B
malloc()
mm_takesemaphore()
heap holder is set to TASK B
<--- preempt
...
task_exit()
Set to current task to
TASK B
Try to release tcb, and
stack memory
free()
mm_takesemaphore()
- Successfully obtain
semaphore because current
task and heap holder is
same.
Free memory....
Heap corrupt.
This change forces all de-allocations via sched_kfree() and sched_ufree()
to be delayed. Eliminating the immediate de-allocation prevents the
above problem with the the re-entrant semaphore because the deallocation
always occurs on the worker thread, never on TASK B.
There could be consequences in the timing of memory availability. We
will see.
Squashed commit of the following:
Fix up some final compile isses.
net/netdev: Convert the network down notification logic to use the new wqueue-based notification factility.
net/udp: Convert the UDP readahead notification logic to use the new wqueue-based notification factility.
net/tcp: Convert the TCP readahead notification logic to use the new wqueue-based notification factility.
mm/iob: Convert the IOB notification logic to use the new wqueue-based notification factility.
sched/wqueue: Signals are not good IPCs to support the target poll functionality for several reasons including the amount of data that can be passed with a signal and in the fact that in protected and kernel modes, user threads executing signal handlers in protected, kernel memory is problematic. Instead, convert the same logic to perform the notifications via function callback on the high priority work queue.
Squashed commit of the following:
mm/iob: The IOB available notifier is now just a wrapper around the common signal notifier.
sched/signal: Add a generic signal notification facility.
sched/signal/sig_evthread.c: More trivial naming changes.
sched/signal: Rename nxsig_notification() to nxsig_evthread() to make forthcoming naming additions more consistent.
Squashed commit of the following:
Add procfs support to show stopped tasks. Add nxsig_action() to solve a chicken and egg problem: We needed to use sigaction to set default actions, but sigaction() would refuse to set actions if the default actions could not be caught or ignored.
sched/signal: Add configuration option to selectively enabled/disable default signal actions for SIGSTOP/SIGSTP/SIGCONT and SIGKILL/SIGINT. Fix some compilation issues.
sched/sched: Okay.. I figured out a way to handle state changes that may occur while they were stopped. If a task/thread was already blocked when SIGSTOP/SIGSTP was received, it will restart in the running state. I will appear that to the task/thread that the blocked condition was interrupt by a signal and returns the EINTR error.
sched/group and sched/sched: Finish framework for continue/resume logic.
sched/signal: Roughing out basic structure to support task suspend/resume
drivers/serial/Kconfig: It is no longer necessary to restrict Ctrl-C handling to the FLAT build
sched/signal: Add a new configuration option to select signal default actions, separate handling of signal default actions from both task startup logic and from the serial TTY Ctrl-C logic. Add a signal set in the group structure to keep track of what signals have been set to the default action. In dispatching signals in PROTECTED or KERNEL mode, use this signal set to determine if the default signal handler is attached and dispatch the signal in kernel mode for the default actions.
drivers/serial: Add Ctrl-C/Ctrl-X support. This is an initial working implementation that still requires that several details be resolved.
sched/task/task_start.c: Add default signal action to SIGKILL.
sched/wqueue: Modify high priority work queue to support multiple threads.
sched/wqueue and libs/libc/wqueue: workqueues don't need set global data to zero since .bss is cleared automatically. Removing this unnecessary initialization also avoids the loss the work items queued before initialization.
Gregory Nutt