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Fix the problem with the C++ exception handling for the multithreaded

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programs.

From the PR description:
The gcc runtime's _Unwind_Find_FDE function, invoked during exception
handling's stack unwinding, is not safe to execute from within multiple
threads. FreeBSD' s dl_iterate_phdr() however permits multiple threads
to pass through it though. The result is surprisingly reliable infinite
looping of one or more threads if they just happen to be unwinding at
the same time.

Introduce the new lock that is write locked around the dl_iterate_pdr,
thus providing required exclusion for the stack unwinders.

PR:	threads/123062
Submitted by:	Andy Newman <an at atrn org>
Reviewed by:	kan
MFC after:	2 weeks
This commit is contained in:
Konstantin Belousov 2008-05-06 09:27:41 +00:00
parent cf181aee60
commit e91ff25c0c
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=178807
3 changed files with 8 additions and 4 deletions
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8
libexec/rtld-elf/rtld.c
View File

@ -2129,9 +2129,10 @@ dl_iterate_phdr(__dl_iterate_hdr_callback callback, void *param)
{
struct dl_phdr_info phdr_info;
const Obj_Entry *obj;
int error, lockstate;
int error, bind_lockstate, phdr_lockstate;
lockstate = rlock_acquire(rtld_bind_lock);
phdr_lockstate = wlock_acquire(rtld_phdr_lock);
bind_lockstate = rlock_acquire(rtld_bind_lock);
error = 0;
@ -2150,7 +2151,8 @@ dl_iterate_phdr(__dl_iterate_hdr_callback callback, void *param)
break;
}
rlock_release(rtld_bind_lock, lockstate);
rlock_release(rtld_bind_lock, bind_lockstate);
wlock_release(rtld_phdr_lock, phdr_lockstate);
return (error);
}

3
libexec/rtld-elf/rtld_lock.c
View File

@ -171,7 +171,7 @@ thread_mask_clear(int mask)
lockinfo.thread_clr_flag(mask);
}
#define RTLD_LOCK_CNT 2
#define RTLD_LOCK_CNT 3
struct rtld_lock {
void *handle;
int mask;
@ -179,6 +179,7 @@ struct rtld_lock {
rtld_lock_t rtld_bind_lock = &rtld_locks[0];
rtld_lock_t rtld_libc_lock = &rtld_locks[1];
rtld_lock_t rtld_phdr_lock = &rtld_locks[2];
int
rlock_acquire(rtld_lock_t lock)

1
libexec/rtld-elf/rtld_lock.h
View File

@ -52,6 +52,7 @@ typedef struct rtld_lock *rtld_lock_t;
extern rtld_lock_t rtld_bind_lock;
extern rtld_lock_t rtld_libc_lock;
extern rtld_lock_t rtld_phdr_lock;
int rlock_acquire(rtld_lock_t);
int wlock_acquire(rtld_lock_t);