From 60f2ceaa8111d9ec51af87bde4a6809f2b3235e4 Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Fri, 28 Feb 2020 11:09:19 -0600 Subject: [PATCH] posix-cpu-timers: Remove unnecessary locking around cpu_clock_sample_group As of e78c3496790e ("time, signal: Protect resource use statistics with seqlock") cpu_clock_sample_group no longers needs siglock protection. Unfortunately no one realized it at the time. Remove the extra locking that is for cpu_clock_sample_group and not for cpu_clock_sample. This significantly simplifies the code. Signed-off-by: "Eric W. Biederman" Signed-off-by: Thomas Gleixner Link: https://lkml.kernel.org/r/878skmvdts.fsf@x220.int.ebiederm.org --- kernel/time/posix-cpu-timers.c | 66 ++++++++---------------------------------- 1 file changed, 12 insertions(+), 54 deletions(-) diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index 46cc188..40c2d83 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -718,31 +718,10 @@ static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp /* * Sample the clock to take the difference with the expiry time. */ - if (CPUCLOCK_PERTHREAD(timer->it_clock)) { + if (CPUCLOCK_PERTHREAD(timer->it_clock)) now = cpu_clock_sample(clkid, p); - } else { - struct sighand_struct *sighand; - unsigned long flags; - - /* - * Protect against sighand release/switch in exit/exec and - * also make timer sampling safe if it ends up calling - * thread_group_cputime(). - */ - sighand = lock_task_sighand(p, &flags); - if (unlikely(sighand == NULL)) { - /* - * The process has been reaped. - * We can't even collect a sample any more. - * Disarm the timer, nothing else to do. - */ - cpu_timer_setexpires(ctmr, 0); - return; - } else { - now = cpu_clock_sample_group(clkid, p, false); - unlock_task_sighand(p, &flags); - } - } + else + now = cpu_clock_sample_group(clkid, p, false); if (now < expires) { itp->it_value = ns_to_timespec64(expires - now); @@ -986,43 +965,22 @@ static void posix_cpu_timer_rearm(struct k_itimer *timer) /* * Fetch the current sample and update the timer's expiry time. */ - if (CPUCLOCK_PERTHREAD(timer->it_clock)) { + if (CPUCLOCK_PERTHREAD(timer->it_clock)) now = cpu_clock_sample(clkid, p); - bump_cpu_timer(timer, now); - if (unlikely(p->exit_state)) - return; - - /* Protect timer list r/w in arm_timer() */ - sighand = lock_task_sighand(p, &flags); - if (!sighand) - return; - } else { - /* - * Protect arm_timer() and timer sampling in case of call to - * thread_group_cputime(). - */ - sighand = lock_task_sighand(p, &flags); - if (unlikely(sighand == NULL)) { - /* - * The process has been reaped. - * We can't even collect a sample any more. - */ - cpu_timer_setexpires(ctmr, 0); - return; - } else if (unlikely(p->exit_state) && thread_group_empty(p)) { - /* If the process is dying, no need to rearm */ - goto unlock; - } + else now = cpu_clock_sample_group(clkid, p, true); - bump_cpu_timer(timer, now); - /* Leave the sighand locked for the call below. */ - } + + bump_cpu_timer(timer, now); + + /* Protect timer list r/w in arm_timer() */ + sighand = lock_task_sighand(p, &flags); + if (unlikely(sighand == NULL)) + return; /* * Now re-arm for the new expiry time. */ arm_timer(timer); -unlock: unlock_task_sighand(p, &flags); } -- 2.7.4