aboutsummaryrefslogtreecommitdiffstats
path: root/include/linux/sched.h
diff options
context:
space:
mode:
authorThomas Gleixner <tglx@linutronix.de>2021-07-29 13:01:59 +0200
committerThomas Gleixner <tglx@linutronix.de>2021-08-28 01:33:02 +0200
commitb542e383d8c005f06a131e2b40d5889b812f19c6 (patch)
tree14a6c55f5366f44df978f27c4b8a92f0a30b0689 /include/linux/sched.h
parentsched/fair: Mark tg_is_idle() an inline in the !CONFIG_FAIR_GROUP_SCHED case (diff)
downloadlinux-dev-b542e383d8c005f06a131e2b40d5889b812f19c6.tar.xz
linux-dev-b542e383d8c005f06a131e2b40d5889b812f19c6.zip
eventfd: Make signal recursion protection a task bit
The recursion protection for eventfd_signal() is based on a per CPU variable and relies on the !RT semantics of spin_lock_irqsave() for protecting this per CPU variable. On RT kernels spin_lock_irqsave() neither disables preemption nor interrupts which allows the spin lock held section to be preempted. If the preempting task invokes eventfd_signal() as well, then the recursion warning triggers. Paolo suggested to protect the per CPU variable with a local lock, but that's heavyweight and actually not necessary. The goal of this protection is to prevent the task stack from overflowing, which can be achieved with a per task recursion protection as well. Replace the per CPU variable with a per task bit similar to other recursion protection bits like task_struct::in_page_owner. This works on both !RT and RT kernels and removes as a side effect the extra per CPU storage. No functional change for !RT kernels. Reported-by: Daniel Bristot de Oliveira <bristot@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Daniel Bristot de Oliveira <bristot@redhat.com> Acked-by: Jason Wang <jasowang@redhat.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Link: https://lore.kernel.org/r/87wnp9idso.ffs@tglx
Diffstat (limited to '')
-rw-r--r--include/linux/sched.h4
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3bb9fecfdaa1..6421a9a8b4ca 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -864,6 +864,10 @@ struct task_struct {
/* Used by page_owner=on to detect recursion in page tracking. */
unsigned in_page_owner:1;
#endif
+#ifdef CONFIG_EVENTFD
+ /* Recursion prevention for eventfd_signal() */
+ unsigned in_eventfd_signal:1;
+#endif
unsigned long atomic_flags; /* Flags requiring atomic access. */