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path: root/kernel/posix-cpu-timers.c
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2005-10-30[PATCH] posix-cpu-timers: fix overrun reportingRoland McGrath
This change corrects an omission in posix_cpu_timer_schedule, so that it correctly propagates the overrun calculation to where it will get reported to the user. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-10-27[PATCH] Yet more posix-cpu-timer fixesRoland McGrath
This just makes sure that a thread's expiry times can't get reset after it clears them in do_exit. This is what allowed us to re-introduce the stricter BUG_ON() check in a362f463a6d316d14daed0f817e151835ce97ff7. Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-10-27Revert "remove false BUG_ON() from run_posix_cpu_timers()"Linus Torvalds
This reverts commit 3de463c7d9d58f8cf3395268230cb20a4c15bffa. Roland has another patch that allows us to leave the BUG_ON() in place by just making sure that the condition it tests for really is always true. That goes in next. Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-10-26[PATCH] Fix cpu timers expiration timeOleg Nesterov
There's a silly off-by-one error in the code that updates the expiration of posix CPU timers, causing them to not be properly updated when they hit exactly on their expiration time (which should be the normal case). This causes them to then fire immediately again, and only _then_ get properly updated. Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-10-26posix cpu timers: fix timer orderingLinus Torvalds
Pointed out by Oleg Nesterov, who has been walking over the code forwards and backwards. Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-10-24[PATCH] posix-timers: fix posix_cpu_timer_set() vs run_posix_cpu_timers() raceOleg Nesterov
This might be harmless, but looks like a race from code inspection (I was unable to trigger it). I must admit, I don't understand why we can't return TIMER_RETRY after 'spin_unlock(&p->sighand->siglock)' without doing bump_cpu_timer(), but this is what original code does. posix_cpu_timer_set: read_lock(&tasklist_lock); spin_lock(&p->sighand->siglock); list_del_init(&timer->it.cpu.entry); spin_unlock(&p->sighand->siglock); We are probaly deleting the timer from run_posix_cpu_timers's 'firing' local list_head while run_posix_cpu_timers() does list_for_each_safe. Various bad things can happen, for example we can just delete this timer so that list_for_each() will not notice it and run_posix_cpu_timers() will not reset '->firing' flag. In that case, .... if (timer->it.cpu.firing) { read_unlock(&tasklist_lock); timer->it.cpu.firing = -1; return TIMER_RETRY; } sys_timer_settime() goes to 'retry:', calls posix_cpu_timer_set() again, it returns TIMER_RETRY ... Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-10-24[PATCH] posix-timers: exit path cleanupOleg Nesterov
No need to rebalance when task exited Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-10-24[PATCH] posix-timers: remove false BUG_ON() from run_posix_cpu_timers()Oleg Nesterov
do_exit() clears ->it_##clock##_expires, but nothing prevents another cpu to attach the timer to exiting process after that. After exit_notify() does 'write_unlock_irq(&tasklist_lock)' and before do_exit() calls 'schedule() local timer interrupt can find tsk->exit_state != 0. If that state was EXIT_DEAD (or another cpu does sys_wait4) interrupted task has ->signal == NULL. At this moment exiting task has no pending cpu timers, they were cleaned up in __exit_signal()->posix_cpu_timers_exit{,_group}(), so we can just return from irq. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-10-24[PATCH] posix-timers: fix cleanup_timers() and run_posix_cpu_timers() racesOleg Nesterov
1. cleanup_timers() sets timer->task = NULL under tasklist + ->sighand locks. That means that this code in posix_cpu_timer_del() and posix_cpu_timer_set() lock_timer(timer); if (timer->task == NULL) return; read_lock(tasklist); put_task_struct(timer->task) is racy. With this patch timer->task modified and accounted only under timer->it_lock. Sadly, this means that dead task_struct won't be freed until timer deleted or armed. 2. run_posix_cpu_timers() collects expired timers into local list under tasklist + ->sighand again. That means that posix_cpu_timer_del() should check timer->it.cpu.firing under these locks too. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-10-23Posix timers: limit number of timers firing at onceLinus Torvalds
Bursty timers aren't good for anybody, very much including latency for other programs when we trigger lots of timers in interrupt context. So set a random limit, after which we'll handle the rest on the next timer tick. Noted by Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-10-21Revert "Fix cpu timers exit deadlock and races"Linus Torvalds
Revert commit e03d13e985d48ac4885382c9e3b1510c78bd047f, to be replaced by a much nicer fix from Roland.
2005-10-19[PATCH] Fix cpu timers exit deadlock and racesRoland McGrath
Oleg Nesterov reported an SMP deadlock. If there is a running timer tracking a different process's CPU time clock when the process owning the timer exits, we deadlock on tasklist_lock in posix_cpu_timer_del via exit_itimers. That code was using tasklist_lock to check for a race with __exit_signal being called on the timer-target task and clearing its ->signal. However, there is actually no such race. __exit_signal will have called posix_cpu_timers_exit and posix_cpu_timers_exit_group before it does that. Those will clear those k_itimer's association with the dying task, so posix_cpu_timer_del will return early and never reach the code in question. In addition, posix_cpu_timer_del called from exit_itimers during execve or directly from timer_delete in the process owning the timer can race with an exiting timer-target task to cause a double put on timer-target task struct. Make sure we always access cpu_timers lists with sighand lock held. Signed-off-by: Roland McGrath <roland@redhat.com> Signed-off-by: Chris Wright <chrisw@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-10-17[PATCH] posix-timers: fix task accountingOleg Nesterov
Make sure we release the task struct properly when releasing pending timers. release_task() does write_lock_irq(&tasklist_lock), so it can't race with run_posix_cpu_timers() on any cpu. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-04-16Linux-2.6.12-rc2Linus Torvalds
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!