From fc558a7496bfab3d29a68953b07a95883fdcfbb1 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Thu, 23 Mar 2006 03:00:05 -0800 Subject: [PATCH] swsusp: finally solve mysqld problem This patch from Pavel moves userland freeze signals handling into more logical place. It now hits even with mysqld running. Signed-off-by: Rafael J. Wysocki Signed-off-by: Pavel Machek Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index ea154104a00b..dfb09ba5c013 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1922,6 +1922,8 @@ int get_signal_to_deliver(siginfo_t *info, struct k_sigaction *return_ka, sigset_t *mask = ¤t->blocked; int signr = 0; + try_to_freeze(); + relock: spin_lock_irq(¤t->sighand->siglock); for (;;) { @@ -2307,7 +2309,6 @@ sys_rt_sigtimedwait(const sigset_t __user *uthese, timeout = schedule_timeout_interruptible(timeout); - try_to_freeze(); spin_lock_irq(¤t->sighand->siglock); sig = dequeue_signal(current, &these, &info); current->blocked = current->real_blocked; -- cgit v1.2.3 From a26fd335b481e0bd14f4e7d1f5e7bb1138b1731f Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Thu, 23 Mar 2006 03:00:49 -0800 Subject: [PATCH] sigprocmask: kill unneeded temp var Cleanup, remove unneeded double copying of current->blocked. Signed-off-by: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index dfb09ba5c013..75f7341b0c39 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2101,10 +2101,11 @@ long do_no_restart_syscall(struct restart_block *param) int sigprocmask(int how, sigset_t *set, sigset_t *oldset) { int error; - sigset_t old_block; spin_lock_irq(¤t->sighand->siglock); - old_block = current->blocked; + if (oldset) + *oldset = current->blocked; + error = 0; switch (how) { case SIG_BLOCK: @@ -2121,8 +2122,7 @@ int sigprocmask(int how, sigset_t *set, sigset_t *oldset) } recalc_sigpending(); spin_unlock_irq(¤t->sighand->siglock); - if (oldset) - *oldset = old_block; + return error; } -- cgit v1.2.3 From fef23e7fbb11a0a78cd61935f7056bc2b237995a Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Tue, 28 Mar 2006 16:10:58 -0800 Subject: [PATCH] exec: allow init to exec from any thread. After looking at the problem of init calling exec some more I figured out an easy way to make the code work. The actual symptom without out this patch is that all threads will die except pid == 1, and the thread calling exec. The thread calling exec will wait forever for pid == 1 to die. Since pid == 1 does not install a handler for SIGKILL it will never die. This modifies the tests for init from current->pid == 1 to the equivalent current == child_reaper. And then it causes exec in the ugly case to modify child_reaper. The only weird symptom is that you wind up with an init process that doesn't have the oldest start time on the box. Signed-off-by: Eric W. Biederman Cc: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index 75f7341b0c39..dc8f91bf9f89 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1990,7 +1990,7 @@ relock: continue; /* Init gets no signals it doesn't want. */ - if (current->pid == 1) + if (current == child_reaper) continue; if (sig_kernel_stop(signr)) { -- cgit v1.2.3 From aa1757f90bea3f598b6e5d04d922a6a60200f1da Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 28 Mar 2006 16:11:12 -0800 Subject: [PATCH] convert sighand_cache to use SLAB_DESTROY_BY_RCU This patch borrows a clever Hugh's 'struct anon_vma' trick. Without tasklist_lock held we can't trust task->sighand until we locked it and re-checked that it is still the same. But this means we don't need to defer 'kmem_cache_free(sighand)'. We can return the memory to slab immediately, all we need is to be sure that sighand->siglock can't dissapear inside rcu protected section. To do so we need to initialize ->siglock inside ctor function, SLAB_DESTROY_BY_RCU does the rest. Signed-off-by: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index dc8f91bf9f89..b0b1ca9daa33 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -330,7 +330,7 @@ void __exit_sighand(struct task_struct *tsk) /* Ok, we're done with the signal handlers */ tsk->sighand = NULL; if (atomic_dec_and_test(&sighand->count)) - sighand_free(sighand); + kmem_cache_free(sighand_cachep, sighand); } void exit_sighand(struct task_struct *tsk) -- cgit v1.2.3 From f63ee72e0fb82e504a0489490babc7612c7cd6c2 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 28 Mar 2006 16:11:13 -0800 Subject: [PATCH] introduce lock_task_sighand() helper Add lock_task_sighand() helper and converts group_send_sig_info() to use it. Hopefully we will have more users soon. This patch also removes '!sighand->count' and '!p->usage' checks, I think they both are bogus, racy and unneeded (but probably it makes sense to restore them as BUG_ON()s). ->sighand is cleared and it's ->count is decremented in release_task() with sighand->siglock held, so it is a bug to have '!p->usage || !->count' after we already locked and verified it is the same. On the other hand, an already dead task without ->sighand can have a non-zero ->usage due to ptrace, for example. If we read the stale value of ->sighand we must see the change after spin_lock(), because that change was done while holding that same old ->sighand.siglock. Signed-off-by: Oleg Nesterov Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 38 ++++++++++++++++++++++++-------------- 1 file changed, 24 insertions(+), 14 deletions(-) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index b0b1ca9daa33..819fa49aa70a 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1120,27 +1120,37 @@ void zap_other_threads(struct task_struct *p) /* * Must be called under rcu_read_lock() or with tasklist_lock read-held. */ +struct sighand_struct *lock_task_sighand(struct task_struct *tsk, unsigned long *flags) +{ + struct sighand_struct *sighand; + + for (;;) { + sighand = rcu_dereference(tsk->sighand); + if (unlikely(sighand == NULL)) + break; + + spin_lock_irqsave(&sighand->siglock, *flags); + if (likely(sighand == tsk->sighand)) + break; + spin_unlock_irqrestore(&sighand->siglock, *flags); + } + + return sighand; +} + int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p) { unsigned long flags; - struct sighand_struct *sp; int ret; -retry: ret = check_kill_permission(sig, info, p); - if (!ret && sig && (sp = rcu_dereference(p->sighand))) { - spin_lock_irqsave(&sp->siglock, flags); - if (p->sighand != sp) { - spin_unlock_irqrestore(&sp->siglock, flags); - goto retry; - } - if ((atomic_read(&sp->count) == 0) || - (atomic_read(&p->usage) == 0)) { - spin_unlock_irqrestore(&sp->siglock, flags); - return -ESRCH; + + if (!ret && sig) { + ret = -ESRCH; + if (lock_task_sighand(p, &flags)) { + ret = __group_send_sig_info(sig, info, p); + unlock_task_sighand(p, &flags); } - ret = __group_send_sig_info(sig, info, p); - spin_unlock_irqrestore(&sp->siglock, flags); } return ret; -- cgit v1.2.3 From a9e88e84b5245da0a1dadb6ccca70ae84e93ccf6 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 28 Mar 2006 16:11:14 -0800 Subject: [PATCH] introduce sig_needs_tasklist() helper In my opinion this patch cleans up the code. Signed-off-by: Oleg Nesterov Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index 819fa49aa70a..c5b65aa4c2bc 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -147,6 +147,9 @@ static kmem_cache_t *sigqueue_cachep; #define sig_kernel_stop(sig) \ (((sig) < SIGRTMIN) && T(sig, SIG_KERNEL_STOP_MASK)) +#define sig_needs_tasklist(sig) \ + (((sig) < SIGRTMIN) && T(sig, SIG_KERNEL_STOP_MASK | M(SIGCONT))) + #define sig_user_defined(t, signr) \ (((t)->sighand->action[(signr)-1].sa.sa_handler != SIG_DFL) && \ ((t)->sighand->action[(signr)-1].sa.sa_handler != SIG_IGN)) @@ -1199,7 +1202,7 @@ kill_proc_info(int sig, struct siginfo *info, pid_t pid) struct task_struct *p; rcu_read_lock(); - if (unlikely(sig_kernel_stop(sig) || sig == SIGCONT)) { + if (unlikely(sig_needs_tasklist(sig))) { read_lock(&tasklist_lock); acquired_tasklist_lock = 1; } -- cgit v1.2.3 From 7001510d0cbf51ad202dd2d0744f54104285cbb9 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 28 Mar 2006 16:11:14 -0800 Subject: [PATCH] copy_process: cleanup bad_fork_cleanup_sighand The only caller of exit_sighand(tsk) is copy_process's error path. We can call __exit_sighand() directly and kill exit_sighand(). This 'tsk' was not yet registered in pid_hash[] or init_task.tasks, it has no external references, nobody can see it, and IF (clone_flags & CLONE_SIGHAND) At least 'current' has a reference to ->sighand, this means atomic_dec_and_test(sighand->count) can't be true. ELSE Nobody can see this ->sighand, this means we can free it without any locking. Signed-off-by: Oleg Nesterov Cc: "Eric W. Biederman" Acked-by: "Paul E. McKenney" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 14 -------------- 1 file changed, 14 deletions(-) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index c5b65aa4c2bc..1d7f4463c32d 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -336,20 +336,6 @@ void __exit_sighand(struct task_struct *tsk) kmem_cache_free(sighand_cachep, sighand); } -void exit_sighand(struct task_struct *tsk) -{ - write_lock_irq(&tasklist_lock); - rcu_read_lock(); - if (tsk->sighand != NULL) { - struct sighand_struct *sighand = rcu_dereference(tsk->sighand); - spin_lock(&sighand->siglock); - __exit_sighand(tsk); - spin_unlock(&sighand->siglock); - } - rcu_read_unlock(); - write_unlock_irq(&tasklist_lock); -} - /* * This function expects the tasklist_lock write-locked. */ -- cgit v1.2.3 From 6b3934ef52712ece50605dfc72e55d00c580831a Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 28 Mar 2006 16:11:16 -0800 Subject: [PATCH] copy_process: cleanup bad_fork_cleanup_signal __exit_signal() does important cleanups atomically under ->siglock. It is also called from copy_process's error path. This is not good, for example we can't move __unhash_process() under ->siglock for that reason. We should not mix these 2 paths, just look at ugly 'if (p->sighand)' under 'bad_fork_cleanup_sighand:' label. For copy_process() case it is sufficient to just backout copy_signal(), nothing more. Again, nobody can see this task yet. For CLONE_THREAD case we just decrement signal->count, otherwise nobody can see this ->signal and we can free it lockless. This patch assumes it is safe to do exit_thread_group_keys() without tasklist_lock. Signed-off-by: Oleg Nesterov Cc: "Eric W. Biederman" Acked-by: David Howells Signed-off-by: Adrian Bunk Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 15 +-------------- 1 file changed, 1 insertion(+), 14 deletions(-) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index 1d7f4463c32d..54e9ef673e68 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -395,23 +395,10 @@ void __exit_signal(struct task_struct *tsk) clear_tsk_thread_flag(tsk,TIF_SIGPENDING); flush_sigqueue(&tsk->pending); if (sig) { - /* - * We are cleaning up the signal_struct here. - */ - exit_thread_group_keys(sig); - kmem_cache_free(signal_cachep, sig); + __cleanup_signal(sig); } } -void exit_signal(struct task_struct *tsk) -{ - atomic_dec(&tsk->signal->live); - - write_lock_irq(&tasklist_lock); - __exit_signal(tsk); - write_unlock_irq(&tasklist_lock); -} - /* * Flush all handlers for a task. */ -- cgit v1.2.3 From 29ff471234d53c7235db287bc52f91884c2977c6 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 28 Mar 2006 16:11:17 -0800 Subject: [PATCH] cleanup __exit_signal() This patch factors out duplicated code under 'if' branches. Also, BUG_ON() conversions and whitespace cleanups. Signed-off-by: Oleg Nesterov Cc: "Eric W. Biederman" Acked-by: "Paul E. McKenney" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 31 +++++++++++++++---------------- 1 file changed, 15 insertions(+), 16 deletions(-) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index 54e9ef673e68..ca1fa854e469 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -341,24 +341,20 @@ void __exit_sighand(struct task_struct *tsk) */ void __exit_signal(struct task_struct *tsk) { - struct signal_struct * sig = tsk->signal; - struct sighand_struct * sighand; + struct signal_struct *sig = tsk->signal; + struct sighand_struct *sighand; + + BUG_ON(!sig); + BUG_ON(!atomic_read(&sig->count)); - if (!sig) - BUG(); - if (!atomic_read(&sig->count)) - BUG(); rcu_read_lock(); sighand = rcu_dereference(tsk->sighand); spin_lock(&sighand->siglock); + posix_cpu_timers_exit(tsk); - if (atomic_dec_and_test(&sig->count)) { + if (atomic_dec_and_test(&sig->count)) posix_cpu_timers_exit_group(tsk); - tsk->signal = NULL; - __exit_sighand(tsk); - spin_unlock(&sighand->siglock); - flush_sigqueue(&sig->shared_pending); - } else { + else { /* * If there is any task waiting for the group exit * then notify it: @@ -369,7 +365,6 @@ void __exit_signal(struct task_struct *tsk) } if (tsk == sig->curr_target) sig->curr_target = next_thread(tsk); - tsk->signal = NULL; /* * Accumulate here the counters for all threads but the * group leader as they die, so they can be added into @@ -387,14 +382,18 @@ void __exit_signal(struct task_struct *tsk) sig->nvcsw += tsk->nvcsw; sig->nivcsw += tsk->nivcsw; sig->sched_time += tsk->sched_time; - __exit_sighand(tsk); - spin_unlock(&sighand->siglock); - sig = NULL; /* Marker for below. */ + sig = NULL; /* Marker for below. */ } + + tsk->signal = NULL; + __exit_sighand(tsk); + spin_unlock(&sighand->siglock); rcu_read_unlock(); + clear_tsk_thread_flag(tsk,TIF_SIGPENDING); flush_sigqueue(&tsk->pending); if (sig) { + flush_sigqueue(&sig->shared_pending); __cleanup_signal(sig); } } -- cgit v1.2.3 From c81addc9d3a0ebff2155e0cd86f90820ab97147e Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 28 Mar 2006 16:11:17 -0800 Subject: [PATCH] rename __exit_sighand to cleanup_sighand Cosmetic, rename __exit_sighand to cleanup_sighand and move it close to copy_sighand(). This matches copy_signal/cleanup_signal naming, and I think it is easier to follow. Signed-off-by: Oleg Nesterov Cc: "Eric W. Biederman" Acked-by: "Paul E. McKenney" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 19 ++----------------- 1 file changed, 2 insertions(+), 17 deletions(-) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index ca1fa854e469..b29c868bd5ee 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -310,9 +310,7 @@ static void flush_sigqueue(struct sigpending *queue) /* * Flush all pending signals for a task. */ - -void -flush_signals(struct task_struct *t) +void flush_signals(struct task_struct *t) { unsigned long flags; @@ -323,19 +321,6 @@ flush_signals(struct task_struct *t) spin_unlock_irqrestore(&t->sighand->siglock, flags); } -/* - * This function expects the tasklist_lock write-locked. - */ -void __exit_sighand(struct task_struct *tsk) -{ - struct sighand_struct * sighand = tsk->sighand; - - /* Ok, we're done with the signal handlers */ - tsk->sighand = NULL; - if (atomic_dec_and_test(&sighand->count)) - kmem_cache_free(sighand_cachep, sighand); -} - /* * This function expects the tasklist_lock write-locked. */ @@ -386,7 +371,7 @@ void __exit_signal(struct task_struct *tsk) } tsk->signal = NULL; - __exit_sighand(tsk); + cleanup_sighand(tsk); spin_unlock(&sighand->siglock); rcu_read_unlock(); -- cgit v1.2.3 From 6a14c5c9da0b4c34b5be783403c54f0396fcfe77 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 28 Mar 2006 16:11:18 -0800 Subject: [PATCH] move __exit_signal() to kernel/exit.c __exit_signal() is private to release_task() now. I think it is better to make it static in kernel/exit.c and export flush_sigqueue() instead - this function is much more simple and straightforward. Signed-off-by: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 65 +-------------------------------------------------------- 1 file changed, 1 insertion(+), 64 deletions(-) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index b29c868bd5ee..6ea49f742a2f 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -22,7 +22,6 @@ #include #include #include -#include #include #include #include @@ -295,7 +294,7 @@ static void __sigqueue_free(struct sigqueue *q) kmem_cache_free(sigqueue_cachep, q); } -static void flush_sigqueue(struct sigpending *queue) +void flush_sigqueue(struct sigpending *queue) { struct sigqueue *q; @@ -321,68 +320,6 @@ void flush_signals(struct task_struct *t) spin_unlock_irqrestore(&t->sighand->siglock, flags); } -/* - * This function expects the tasklist_lock write-locked. - */ -void __exit_signal(struct task_struct *tsk) -{ - struct signal_struct *sig = tsk->signal; - struct sighand_struct *sighand; - - BUG_ON(!sig); - BUG_ON(!atomic_read(&sig->count)); - - rcu_read_lock(); - sighand = rcu_dereference(tsk->sighand); - spin_lock(&sighand->siglock); - - posix_cpu_timers_exit(tsk); - if (atomic_dec_and_test(&sig->count)) - posix_cpu_timers_exit_group(tsk); - else { - /* - * If there is any task waiting for the group exit - * then notify it: - */ - if (sig->group_exit_task && atomic_read(&sig->count) == sig->notify_count) { - wake_up_process(sig->group_exit_task); - sig->group_exit_task = NULL; - } - if (tsk == sig->curr_target) - sig->curr_target = next_thread(tsk); - /* - * Accumulate here the counters for all threads but the - * group leader as they die, so they can be added into - * the process-wide totals when those are taken. - * The group leader stays around as a zombie as long - * as there are other threads. When it gets reaped, - * the exit.c code will add its counts into these totals. - * We won't ever get here for the group leader, since it - * will have been the last reference on the signal_struct. - */ - sig->utime = cputime_add(sig->utime, tsk->utime); - sig->stime = cputime_add(sig->stime, tsk->stime); - sig->min_flt += tsk->min_flt; - sig->maj_flt += tsk->maj_flt; - sig->nvcsw += tsk->nvcsw; - sig->nivcsw += tsk->nivcsw; - sig->sched_time += tsk->sched_time; - sig = NULL; /* Marker for below. */ - } - - tsk->signal = NULL; - cleanup_sighand(tsk); - spin_unlock(&sighand->siglock); - rcu_read_unlock(); - - clear_tsk_thread_flag(tsk,TIF_SIGPENDING); - flush_sigqueue(&tsk->pending); - if (sig) { - flush_sigqueue(&sig->shared_pending); - __cleanup_signal(sig); - } -} - /* * Flush all handlers for a task. */ -- cgit v1.2.3 From 6108ccd3e2f3012d5eec582e0af4d75e693824da Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 28 Mar 2006 16:11:22 -0800 Subject: [PATCH] relax sig_needs_tasklist() handle_stop_signal() does not need tasklist_lock for SIG_KERNEL_STOP_MASK signals anymore. Signed-off-by: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index 6ea49f742a2f..e99ec2f891a0 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -146,8 +146,7 @@ static kmem_cache_t *sigqueue_cachep; #define sig_kernel_stop(sig) \ (((sig) < SIGRTMIN) && T(sig, SIG_KERNEL_STOP_MASK)) -#define sig_needs_tasklist(sig) \ - (((sig) < SIGRTMIN) && T(sig, SIG_KERNEL_STOP_MASK | M(SIGCONT))) +#define sig_needs_tasklist(sig) ((sig) == SIGCONT) #define sig_user_defined(t, signr) \ (((t)->sighand->action[(signr)-1].sa.sa_handler != SIG_DFL) && \ -- cgit v1.2.3 From a122b341b74c08020f6521b615acca6a692aac79 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 28 Mar 2006 16:11:22 -0800 Subject: [PATCH] do_signal_stop: don't take tasklist_lock do_signal_stop() does not need tasklist_lock anymore. So it does not need to do misc re-checks, and we can simplify the code. Signed-off-by: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 69 ++++++++++++++------------------------------------------- 1 file changed, 17 insertions(+), 52 deletions(-) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index e99ec2f891a0..e3bdec914626 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1682,8 +1682,7 @@ out: * Returns nonzero if we've actually stopped and released the siglock. * Returns zero if we didn't stop and still hold the siglock. */ -static int -do_signal_stop(int signr) +static int do_signal_stop(int signr) { struct signal_struct *sig = current->signal; struct sighand_struct *sighand = current->sighand; @@ -1703,7 +1702,6 @@ do_signal_stop(int signr) set_current_state(TASK_STOPPED); if (stop_count == 0) sig->flags = SIGNAL_STOP_STOPPED; - spin_unlock_irq(&sighand->siglock); } else if (thread_group_empty(current)) { /* @@ -1712,71 +1710,38 @@ do_signal_stop(int signr) current->exit_code = current->signal->group_exit_code = signr; set_current_state(TASK_STOPPED); sig->flags = SIGNAL_STOP_STOPPED; - spin_unlock_irq(&sighand->siglock); } else { /* + * (sig->group_stop_count == 0) * There is no group stop already in progress. - * We must initiate one now, but that requires - * dropping siglock to get both the tasklist lock - * and siglock again in the proper order. Note that - * this allows an intervening SIGCONT to be posted. - * We need to check for that and bail out if necessary. + * We must initiate one now. */ struct task_struct *t; - spin_unlock_irq(&sighand->siglock); - - /* signals can be posted during this window */ - - read_lock(&tasklist_lock); - spin_lock_irq(&sighand->siglock); + current->exit_code = signr; + sig->group_exit_code = signr; - if (!likely(sig->flags & SIGNAL_STOP_DEQUEUED)) { + stop_count = 0; + for (t = next_thread(current); t != current; t = next_thread(t)) /* - * Another stop or continue happened while we - * didn't have the lock. We can just swallow this - * signal now. If we raced with a SIGCONT, that - * should have just cleared it now. If we raced - * with another processor delivering a stop signal, - * then the SIGCONT that wakes us up should clear it. + * Setting state to TASK_STOPPED for a group + * stop is always done with the siglock held, + * so this check has no races. */ - read_unlock(&tasklist_lock); - return 0; - } - - if (sig->group_stop_count == 0) { - sig->group_exit_code = signr; - stop_count = 0; - for (t = next_thread(current); t != current; - t = next_thread(t)) - /* - * Setting state to TASK_STOPPED for a group - * stop is always done with the siglock held, - * so this check has no races. - */ - if (!t->exit_state && - !(t->state & (TASK_STOPPED|TASK_TRACED))) { - stop_count++; - signal_wake_up(t, 0); - } - sig->group_stop_count = stop_count; - } - else { - /* A race with another thread while unlocked. */ - signr = sig->group_exit_code; - stop_count = --sig->group_stop_count; - } + if (!t->exit_state && + !(t->state & (TASK_STOPPED|TASK_TRACED))) { + stop_count++; + signal_wake_up(t, 0); + } + sig->group_stop_count = stop_count; - current->exit_code = signr; set_current_state(TASK_STOPPED); if (stop_count == 0) sig->flags = SIGNAL_STOP_STOPPED; - - spin_unlock_irq(&sighand->siglock); - read_unlock(&tasklist_lock); } + spin_unlock_irq(&sighand->siglock); finish_stop(stop_count); return 1; } -- cgit v1.2.3 From 88531f725bd52e37a7be726860e4ff3f09031d89 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 28 Mar 2006 16:11:24 -0800 Subject: [PATCH] do_sigaction: don't take tasklist_lock do_sigaction() does not need tasklist_lock anymore, we can simplify the code. Signed-off-by: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 22 +++------------------- 1 file changed, 3 insertions(+), 19 deletions(-) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index e3bdec914626..2dfaa5076c31 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2301,8 +2301,7 @@ sys_rt_sigqueueinfo(int pid, int sig, siginfo_t __user *uinfo) return kill_proc_info(sig, &info, pid); } -int -do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact) +int do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact) { struct k_sigaction *k; sigset_t mask; @@ -2328,6 +2327,7 @@ do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact) if (act) { sigdelsetmask(&act->sa.sa_mask, sigmask(SIGKILL) | sigmask(SIGSTOP)); + *k = *act; /* * POSIX 3.3.1.3: * "Setting a signal action to SIG_IGN for a signal that is @@ -2340,19 +2340,8 @@ do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact) * be discarded, whether or not it is blocked" */ if (act->sa.sa_handler == SIG_IGN || - (act->sa.sa_handler == SIG_DFL && - sig_kernel_ignore(sig))) { - /* - * This is a fairly rare case, so we only take the - * tasklist_lock once we're sure we'll need it. - * Now we must do this little unlock and relock - * dance to maintain the lock hierarchy. - */ + (act->sa.sa_handler == SIG_DFL && sig_kernel_ignore(sig))) { struct task_struct *t = current; - spin_unlock_irq(&t->sighand->siglock); - read_lock(&tasklist_lock); - spin_lock_irq(&t->sighand->siglock); - *k = *act; sigemptyset(&mask); sigaddset(&mask, sig); rm_from_queue_full(&mask, &t->signal->shared_pending); @@ -2361,12 +2350,7 @@ do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact) recalc_sigpending_tsk(t); t = next_thread(t); } while (t != current); - spin_unlock_irq(¤t->sighand->siglock); - read_unlock(&tasklist_lock); - return 0; } - - *k = *act; } spin_unlock_irq(¤t->sighand->siglock); -- cgit v1.2.3 From dac27f4a09c274db048e80d2511102e540ac9e3a Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 28 Mar 2006 16:11:28 -0800 Subject: [PATCH] simplify do_signal_stop() do_signal_stop() considers 'thread_group_empty()' as a special case. This was needed to avoid taking tasklist_lock. Since this lock is unneeded any longer, we can remove this special case and simplify the code even more. Also, before this patch, finish_stop() was called with stop_count == -1 for 'thread_group_empty()' case. This is not strictly wrong, but confusing and unneeded. Signed-off-by: Oleg Nesterov Cc: john stultz Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 32 ++++++++------------------------ 1 file changed, 8 insertions(+), 24 deletions(-) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index 2dfaa5076c31..efba39626e66 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1685,8 +1685,7 @@ out: static int do_signal_stop(int signr) { struct signal_struct *sig = current->signal; - struct sighand_struct *sighand = current->sighand; - int stop_count = -1; + int stop_count; if (!likely(sig->flags & SIGNAL_STOP_DEQUEUED)) return 0; @@ -1696,30 +1695,14 @@ static int do_signal_stop(int signr) * There is a group stop in progress. We don't need to * start another one. */ - signr = sig->group_exit_code; stop_count = --sig->group_stop_count; - current->exit_code = signr; - set_current_state(TASK_STOPPED); - if (stop_count == 0) - sig->flags = SIGNAL_STOP_STOPPED; - } - else if (thread_group_empty(current)) { - /* - * Lock must be held through transition to stopped state. - */ - current->exit_code = current->signal->group_exit_code = signr; - set_current_state(TASK_STOPPED); - sig->flags = SIGNAL_STOP_STOPPED; - } - else { + } else { /* - * (sig->group_stop_count == 0) * There is no group stop already in progress. * We must initiate one now. */ struct task_struct *t; - current->exit_code = signr; sig->group_exit_code = signr; stop_count = 0; @@ -1735,13 +1718,14 @@ static int do_signal_stop(int signr) signal_wake_up(t, 0); } sig->group_stop_count = stop_count; - - set_current_state(TASK_STOPPED); - if (stop_count == 0) - sig->flags = SIGNAL_STOP_STOPPED; } - spin_unlock_irq(&sighand->siglock); + if (stop_count == 0) + sig->flags = SIGNAL_STOP_STOPPED; + current->exit_code = sig->group_exit_code; + __set_current_state(TASK_STOPPED); + + spin_unlock_irq(¤t->sighand->siglock); finish_stop(stop_count); return 1; } -- cgit v1.2.3 From 883606a7c9e84e206f96c38f88c4bd66df72f51e Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 28 Mar 2006 16:11:28 -0800 Subject: [PATCH] finish_stop: don't check stop_count < 0 Remove an obscure 'stop_count < 0' check in finish_stop(). The previous patch made this case impossible. Signed-off-by: Oleg Nesterov Cc: john stultz Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index efba39626e66..24d5059ab0a9 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1657,7 +1657,7 @@ finish_stop(int stop_count) * a group stop in progress and we are the last to stop, * report to the parent. When ptraced, every thread reports itself. */ - if (stop_count < 0 || (current->ptrace & PT_PTRACED)) + if (current->ptrace & PT_PTRACED) to_self = 1; else if (stop_count == 0) to_self = 0; -- cgit v1.2.3 From a1d5e21e3e388fb2c16463d007e788b1e41b74f1 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 28 Mar 2006 16:11:29 -0800 Subject: [PATCH] do_notify_parent_cldstop: remove 'to_self' param The previous patch has changed callsites of do_notify_parent_cldstop() so that to_self == (->ptrace & PT_PTRACED) always (as it should be). We can remove this parameter now. Signed-off-by: Oleg Nesterov Cc: john stultz Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 32 +++++++++++--------------------- 1 file changed, 11 insertions(+), 21 deletions(-) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index 24d5059ab0a9..0528a959daa9 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -591,9 +591,7 @@ static int check_kill_permission(int sig, struct siginfo *info, } /* forward decl */ -static void do_notify_parent_cldstop(struct task_struct *tsk, - int to_self, - int why); +static void do_notify_parent_cldstop(struct task_struct *tsk, int why); /* * Handle magic process-wide effects of stop/continue signals. @@ -643,7 +641,7 @@ static void handle_stop_signal(int sig, struct task_struct *p) p->signal->group_stop_count = 0; p->signal->flags = SIGNAL_STOP_CONTINUED; spin_unlock(&p->sighand->siglock); - do_notify_parent_cldstop(p, (p->ptrace & PT_PTRACED), CLD_STOPPED); + do_notify_parent_cldstop(p, CLD_STOPPED); spin_lock(&p->sighand->siglock); } rm_from_queue(SIG_KERNEL_STOP_MASK, &p->signal->shared_pending); @@ -684,7 +682,7 @@ static void handle_stop_signal(int sig, struct task_struct *p) p->signal->flags = SIGNAL_STOP_CONTINUED; p->signal->group_exit_code = 0; spin_unlock(&p->sighand->siglock); - do_notify_parent_cldstop(p, (p->ptrace & PT_PTRACED), CLD_CONTINUED); + do_notify_parent_cldstop(p, CLD_CONTINUED); spin_lock(&p->sighand->siglock); } else { /* @@ -1519,14 +1517,14 @@ void do_notify_parent(struct task_struct *tsk, int sig) spin_unlock_irqrestore(&psig->siglock, flags); } -static void do_notify_parent_cldstop(struct task_struct *tsk, int to_self, int why) +static void do_notify_parent_cldstop(struct task_struct *tsk, int why) { struct siginfo info; unsigned long flags; struct task_struct *parent; struct sighand_struct *sighand; - if (to_self) + if (tsk->ptrace & PT_PTRACED) parent = tsk->parent; else { tsk = tsk->group_leader; @@ -1601,7 +1599,7 @@ static void ptrace_stop(int exit_code, int nostop_code, siginfo_t *info) !(current->ptrace & PT_ATTACHED)) && (likely(current->parent->signal != current->signal) || !unlikely(current->signal->flags & SIGNAL_GROUP_EXIT))) { - do_notify_parent_cldstop(current, 1, CLD_TRAPPED); + do_notify_parent_cldstop(current, CLD_TRAPPED); read_unlock(&tasklist_lock); schedule(); } else { @@ -1650,25 +1648,17 @@ void ptrace_notify(int exit_code) static void finish_stop(int stop_count) { - int to_self; - /* * If there are no other threads in the group, or if there is * a group stop in progress and we are the last to stop, * report to the parent. When ptraced, every thread reports itself. */ - if (current->ptrace & PT_PTRACED) - to_self = 1; - else if (stop_count == 0) - to_self = 0; - else - goto out; - - read_lock(&tasklist_lock); - do_notify_parent_cldstop(current, to_self, CLD_STOPPED); - read_unlock(&tasklist_lock); + if (stop_count == 0 || (current->ptrace & PT_PTRACED)) { + read_lock(&tasklist_lock); + do_notify_parent_cldstop(current, CLD_STOPPED); + read_unlock(&tasklist_lock); + } -out: schedule(); /* * Now we don't run again until continued. -- cgit v1.2.3 From 547679087bc60277d11b11631d826895762c4505 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 28 Mar 2006 16:11:30 -0800 Subject: [PATCH] send_sigqueue: simplify and fix the race send_sigqueue() checks PF_EXITING, then locks p->sighand->siglock. This is unsafe: 'p' can exit in between and set ->sighand = NULL. The race is theoretical, the window is tiny and irqs are disabled by the caller, so I don't think we need the fix for -stable tree. Convert send_sigqueue() to use lock_task_sighand() helper. Also, delete 'p->flags & PF_EXITING' re-check, it is unneeded and the comment is wrong. Signed-off-by: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/signal.c | 41 ++++------------------------------------- 1 file changed, 4 insertions(+), 37 deletions(-) (limited to 'kernel/signal.c') diff --git a/kernel/signal.c b/kernel/signal.c index 0528a959daa9..4922928d91f6 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1309,12 +1309,10 @@ void sigqueue_free(struct sigqueue *q) __sigqueue_free(q); } -int -send_sigqueue(int sig, struct sigqueue *q, struct task_struct *p) +int send_sigqueue(int sig, struct sigqueue *q, struct task_struct *p) { unsigned long flags; int ret = 0; - struct sighand_struct *sh; BUG_ON(!(q->flags & SIGQUEUE_PREALLOC)); @@ -1328,48 +1326,17 @@ send_sigqueue(int sig, struct sigqueue *q, struct task_struct *p) */ rcu_read_lock(); - if (unlikely(p->flags & PF_EXITING)) { + if (!likely(lock_task_sighand(p, &flags))) { ret = -1; goto out_err; } -retry: - sh = rcu_dereference(p->sighand); - - spin_lock_irqsave(&sh->siglock, flags); - if (p->sighand != sh) { - /* We raced with exec() in a multithreaded process... */ - spin_unlock_irqrestore(&sh->siglock, flags); - goto retry; - } - - /* - * We do the check here again to handle the following scenario: - * - * CPU 0 CPU 1 - * send_sigqueue - * check PF_EXITING - * interrupt exit code running - * __exit_signal - * lock sighand->siglock - * unlock sighand->siglock - * lock sh->siglock - * add(tsk->pending) flush_sigqueue(tsk->pending) - * - */ - - if (unlikely(p->flags & PF_EXITING)) { - ret = -1; - goto out; - } - if (unlikely(!list_empty(&q->list))) { /* * If an SI_TIMER entry is already queue just increment * the overrun count. */ - if (q->info.si_code != SI_TIMER) - BUG(); + BUG_ON(q->info.si_code != SI_TIMER); q->info.si_overrun++; goto out; } @@ -1385,7 +1352,7 @@ retry: signal_wake_up(p, sig == SIGKILL); out: - spin_unlock_irqrestore(&sh->siglock, flags); + unlock_task_sighand(p, &flags); out_err: rcu_read_unlock(); -- cgit v1.2.3