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Currently, the debugger attached to the process executing vfork() does

Browse Source 
not get syscall exit notification until the child performed exec of
exit.  Swap the order of doing ptracestop() and waiting for P_PPWAIT
clearing, by postponing the wait into syscallret after ptracestop()
notification is done.

Reported, tested and reviewed by:	Dmitry Mikulin <dmitrym juniper net>
MFC after:	 2 weeks
This commit is contained in:
Konstantin Belousov 2012-02-27 21:10:10 +00:00
parent 963a74f13c
commit 1d7ca9bb8e
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=232240
3 changed files with 26 additions and 9 deletions
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12
sys/kern/kern_fork.c
View File

@ -708,6 +708,10 @@ do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2,
_PHOLD(p2);
p2_held = 1;
}
if (flags & RFPPWAIT) {
td->td_pflags |= TDP_RFPPWAIT;
td->td_rfppwait_p = p2;
}
PROC_UNLOCK(p2);
if ((flags & RFSTOPPED) == 0) {
/*
@ -740,14 +744,6 @@ do_fork(struct thread *td, int flags, struct proc *p2, struct thread *td2,
cv_wait(&p2->p_dbgwait, &p2->p_mtx);
if (p2_held)
_PRELE(p2);
/*
* Preserve synchronization semantics of vfork. If waiting for
* child to exec or exit, set P_PPWAIT on child, and sleep on our
* proc (in case of exit).
*/
while (p2->p_flag & P_PPWAIT)
cv_wait(&p2->p_pwait, &p2->p_mtx);
PROC_UNLOCK(p2);
}

21
sys/kern/subr_syscall.c
View File

@ -165,7 +165,7 @@ syscallenter(struct thread *td, struct syscall_args *sa)
static inline void
syscallret(struct thread *td, int error, struct syscall_args *sa __unused)
{
struct proc *p;
struct proc *p, *p2;
int traced;
p = td->td_proc;
@ -223,4 +223,23 @@ syscallret(struct thread *td, int error, struct syscall_args *sa __unused)
td->td_dbgflags &= ~(TDB_SCX | TDB_EXEC | TDB_FORK);
PROC_UNLOCK(p);
}
if (td->td_pflags & TDP_RFPPWAIT) {
/*
* Preserve synchronization semantics of vfork. If
* waiting for child to exec or exit, fork set
* P_PPWAIT on child, and there we sleep on our proc
* (in case of exit).
*
* Do it after the ptracestop() above is finished, to
* not block our debugger until child execs or exits
* to finish vfork wait.
*/
td->td_pflags &= ~TDP_RFPPWAIT;
p2 = td->td_rfppwait_p;
PROC_LOCK(p2);
while (p2->p_flag & P_PPWAIT)
cv_wait(&p2->p_pwait, &p2->p_mtx);
PROC_UNLOCK(p2);
}
}

2
sys/sys/proc.h
View File

@ -311,6 +311,7 @@ struct thread {
struct vnet *td_vnet; /* (k) Effective vnet. */
const char *td_vnet_lpush; /* (k) Debugging vnet push / pop. */
struct trapframe *td_intr_frame;/* (k) Frame of the current irq */
struct proc *td_rfppwait_p; /* (k) The vforked child */
};
struct mtx *thread_lock_block(struct thread *);
@ -415,6 +416,7 @@ do { \
#define TDP_CALLCHAIN 0x00400000 /* Capture thread's callchain */
#define TDP_IGNSUSP 0x00800000 /* Permission to ignore the MNTK_SUSPEND* */
#define TDP_AUDITREC 0x01000000 /* Audit record pending on thread */
#define TDP_RFPPWAIT 0x02000000 /* Handle RFPPWAIT on syscall exit */
/*
* Reasons that the current thread can not be run yet.