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signalfd simplification

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This simplifies signalfd code, by avoiding it to remain attached to the
sighand during its lifetime.

In this way, the signalfd remain attached to the sighand only during
poll(2) (and select and epoll) and read(2).  This also allows to remove
all the custom "tsk == current" checks in kernel/signal.c, since
dequeue_signal() will only be called by "current".

I think this is also what Ben was suggesting time ago.

The external effect of this, is that a thread can extract only its own
private signals and the group ones.  I think this is an acceptable
behaviour, in that those are the signals the thread would be able to
fetch w/out signalfd.

Signed-off-by: Davide Libenzi <davidel@xmailserver.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Davide Libenzi
2007-09-20 12:40:16 -07:00
committed by Linus Torvalds
parent 9db619e665
commit b8fceee17a
8 changed files with 39 additions and 217 deletions
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9
kernel/exit.c
View File

@@ -24,7 +24,6 @@
#include <linux/pid_namespace.h>
#include <linux/ptrace.h>
#include <linux/profile.h>
#include <linux/signalfd.h>
#include <linux/mount.h>
#include <linux/proc_fs.h>
#include <linux/kthread.h>
@@ -86,14 +85,6 @@ static void __exit_signal(struct task_struct *tsk)
sighand = rcu_dereference(tsk->sighand);
spin_lock(&sighand->siglock);
/*
* Notify that this sighand has been detached. This must
* be called with the tsk->sighand lock held. Also, this
* access tsk->sighand internally, so it must be called
* before tsk->sighand is reset.
*/
signalfd_detach_locked(tsk);
posix_cpu_timers_exit(tsk);
if (atomic_dec_and_test(&sig->count))
posix_cpu_timers_exit_group(tsk);

2
kernel/fork.c
View File

@@ -1438,7 +1438,7 @@ static void sighand_ctor(void *data, struct kmem_cache *cachep,
struct sighand_struct *sighand = data;
spin_lock_init(&sighand->siglock);
INIT_LIST_HEAD(&sighand->signalfd_list);
init_waitqueue_head(&sighand->signalfd_wqh);
}
void __init proc_caches_init(void)

8
kernel/signal.c
View File

@@ -378,8 +378,7 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
/* We only dequeue private signals from ourselves, we don't let
* signalfd steal them
*/
if (likely(tsk == current))
signr = __dequeue_signal(&tsk->pending, mask, info);
signr = __dequeue_signal(&tsk->pending, mask, info);
if (!signr) {
signr = __dequeue_signal(&tsk->signal->shared_pending,
mask, info);
@@ -407,8 +406,7 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
}
}
}
if (likely(tsk == current))
recalc_sigpending();
recalc_sigpending();
if (signr && unlikely(sig_kernel_stop(signr))) {
/*
* Set a marker that we have dequeued a stop signal. Our
@@ -425,7 +423,7 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info)
if (!(tsk->signal->flags & SIGNAL_GROUP_EXIT))
tsk->signal->flags |= SIGNAL_STOP_DEQUEUED;
}
if (signr && likely(tsk == current) &&
if (signr &&
((info->si_code & __SI_MASK) == __SI_TIMER) &&
info->si_sys_private){
/*