1. Process p1 is currently being swapped in.
2. Process p2 calls linux_ptrace(PTRACE_GETFPXREGS, p1_pid, ...)
3. After acquiring a reference to FIRST_THREAD_IN_PROC(p1),
p2 blocks in faultin() while p1 finishes being swapped in.
This means p2 won't get back the lock on p1 until after p1's
threads are runnable.
4. After p1 is swapped in, the first thread in p1 exits.
5. p2 now uses its dangling reference to p1's first thread.
if compiling with I686_CPU as a target. CPU_DISABLE_SSE will prevent
this from happening and will guarantee the code is not compiled in.
I am still not happy with this, but gcc is now generating code that uses
these instructions if you set CPUTYPE to p3/p4 or athlon-4/mp/xp or higher.
The ability to schedule multiple threads per process
(one one cpu) by making ALL system calls optionally asynchronous.
to come: ia64 and power-pc patches, patches for gdb, test program (in tools)
Reviewed by: Almost everyone who counts
(at various times, peter, jhb, matt, alfred, mini, bernd,
and a cast of thousands)
NOTE: this is still Beta code, and contains lots of debugging stuff.
expect slight instability in signals..
checking, followed by a lookup of the process. Do not call
ptrace() for permission checking, but do it inline.
Spotted by: rwatson
o While here, copy-in arguments before we lock. This fixes
a possible permanent lock.
Reviewed by: rwatson
