user/sven/linux.git/include/linux/rcutiny.h, branch v5.15.69

rcu: Remove special bit at the bottom of the ->dynticks counter

2021-08-06T20:41:48Z

Commit b8c17e6664c4 ("rcu: Maintain special bits at bottom of ->dynticks counter") reserved a bit at the bottom of the ->dynticks counter to defer flushing of TLBs, but this facility never has been used. This commit therefore removes this capability along with the rcu_eqs_special_set() function used to trigger it. Link: https://lore.kernel.org/linux-doc/CALCETrWNPOOdTrFabTDd=H7+wc6xJ9rJceg6OL1S0rTV5pfSsA@mail.gmail.com/ Suggested-by: Andy Lutomirski Signed-off-by: "Joel Fernandes (Google)" [ paulmck: Forward-port to v5.13-rc1. ] Signed-off-by: Paul E. McKenney

rcu: Remove the unused rcu_irq_exit_preempt() function

2021-05-10T23:22:53Z

Commit 9ee01e0f69a9 ("x86/entry: Clean up idtentry_enter/exit() leftovers") left the rcu_irq_exit_preempt() in place in order to avoid conflicts with the -rcu tree. Now that this change has long since hit mainline, this commit removes the no-longer-used rcu_irq_exit_preempt() function. Signed-off-by: Paul E. McKenney

rcu: Provide polling interfaces for Tiny RCU grace periods

2021-03-25T00:16:15Z

There is a need for a non-blocking polling interface for RCU grace periods, so this commit supplies start_poll_synchronize_rcu() and poll_state_synchronize_rcu() for this purpose. Note that the existing get_state_synchronize_rcu() may be used if future grace periods are inevitable (perhaps due to a later call_rcu() invocation). The new start_poll_synchronize_rcu() is to be used if future grace periods might not otherwise happen. Finally, poll_state_synchronize_rcu() provides a lockless check for a grace period having elapsed since the corresponding call to either of the get_state_synchronize_rcu() or start_poll_synchronize_rcu(). As with get_state_synchronize_rcu(), the return value from either get_state_synchronize_rcu() or start_poll_synchronize_rcu() is passed in to a later call to either poll_state_synchronize_rcu() or the existing (might_sleep) cond_synchronize_rcu(). [ paulmck: Revert cond_synchronize_rcu() to might_sleep() per Frederic Weisbecker feedback. ] Reviewed-by: Frederic Weisbecker Signed-off-by: Paul E. McKenney

x86/cpu: Avoid cpuinfo-induced IPIing of idle CPUs

2020-11-07T00:59:11Z

Currently, accessing /proc/cpuinfo sends IPIs to idle CPUs in order to learn their clock frequency. Which is a bit strange, given that waking them from idle likely significantly changes their clock frequency. This commit therefore avoids sending /proc/cpuinfo-induced IPIs to idle CPUs. [ paulmck: Also check for idle in arch_freq_prepare_all(). ] Signed-off-by: Paul E. McKenney Cc: Rafael J. Wysocki Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: "H. Peter Anvin" Cc:

rcu: Remove unused __rcu_is_watching() function

2020-08-25T01:37:56Z

The x86/entry work removed all uses of __rcu_is_watching(), therefore this commit removes it entirely. Cc: Andy Lutomirski Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: "H. Peter Anvin" Cc: Signed-off-by: Paul E. McKenney

rcu: Support reclaim for head-less object

2020-06-29T18:59:26Z

Update the kvfree_call_rcu() function with head-less support. This allows RCU to reclaim objects without an embedded rcu_head. tree-RCU: We introduce two chains of arrays to store SLAB-backed and vmalloc pointers, each. Storage in either of these arrays does not require embedding an rcu_head within the object. Maintaining the arrays may become impossible due to high memory pressure. For such cases there is an emergency path. Objects with rcu_head inside are just queued on a backup rcu_head list. Later on that list is drained. As for the head-less variant, as the current context can sleep, the following emergency measures are applied: a) Synchronously wait until a grace period has elapsed. b) Call kvfree(). tiny-RCU: For double argument calls, there are no new changes in behavior. For single argument call, kvfree() is directly inlined on the current stack after a synchronize_rcu() call. Note that for tiny-RCU, any call to synchronize_rcu() is actually a quiescent state, therefore it does nothing. Reviewed-by: Joel Fernandes (Google) Signed-off-by: Uladzislau Rezki (Sony) Signed-off-by: Joel Fernandes (Google) Co-developed-by: Joel Fernandes (Google) Signed-off-by: Paul E. McKenney

rcu: Rename _kfree_callback/_kfree_rcu_offset/kfree_call_*

2020-06-29T18:59:25Z

The following changes are introduced: 1. Rename rcu_invoke_kfree_callback() to rcu_invoke_kvfree_callback(), as well as the associated trace events, so the rcu_kfree_callback(), becomes rcu_kvfree_callback(). The reason is to be aligned with kvfree() notation. 2. Rename __is_kfree_rcu_offset to __is_kvfree_rcu_offset. All RCU paths use kvfree() now instead of kfree(), thus rename it. 3. Rename kfree_call_rcu() to the kvfree_call_rcu(). The reason is, it is capable of freeing vmalloc() memory now. Do the same with __kfree_rcu() macro, it becomes __kvfree_rcu(), the goal is the same. Reviewed-by: Joel Fernandes (Google) Co-developed-by: Joel Fernandes (Google) Signed-off-by: Joel Fernandes (Google) Signed-off-by: Uladzislau Rezki (Sony) Signed-off-by: Paul E. McKenney

rcu: Provide rcu_irq_exit_check_preempt()

2020-05-26T17:05:11Z

Provide a debug check which can be invoked from exception return to kernel mode before an attempt is made to schedule. Warn if RCU is not ready for this. Signed-off-by: Thomas Gleixner Signed-off-by: Ingo Molnar Cc: Paul E. McKenney Link: https://lore.kernel.org/r/20200521202117.089709607@linutronix.de

rcu: Provide __rcu_is_watching()

2020-05-19T13:51:21Z

Same as rcu_is_watching() but without the preempt_disable/enable() pair inside the function. It is merked noinstr so it ends up in the non-instrumentable text section. This is useful for non-preemptible code especially in the low level entry section. Using rcu_is_watching() there results in a call to the preempt_schedule_notrace() thunk which triggers noinstr section warnings in objtool. Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra Link: https://lkml.kernel.org/r/20200512213810.518709291@linutronix.de

rcu: Provide rcu_irq_exit_preempt()

2020-05-19T13:51:21Z

Interrupts and exceptions invoke rcu_irq_enter() on entry and need to invoke rcu_irq_exit() before they either return to the interrupted code or invoke the scheduler due to preemption. The general assumption is that RCU idle code has to have preemption disabled so that a return from interrupt cannot schedule. So the return from interrupt code invokes rcu_irq_exit() and preempt_schedule_irq(). If there is any imbalance in the rcu_irq/nmi* invocations or RCU idle code had preemption enabled then this goes unnoticed until the CPU goes idle or some other RCU check is executed. Provide rcu_irq_exit_preempt() which can be invoked from the interrupt/exception return code in case that preemption is enabled. It invokes rcu_irq_exit() and contains a few sanity checks in case that CONFIG_PROVE_RCU is enabled to catch such issues directly. Signed-off-by: Thomas Gleixner Reviewed-by: Paul E. McKenney Reviewed-by: Alexandre Chartre Acked-by: Peter Zijlstra Link: https://lkml.kernel.org/r/20200505134904.364456424@linutronix.de

user/sven/linux.git/include/linux/rcutiny.h, branch v5.15.69

rcu: Remove special bit at the bottom of the ->dynticks counter

rcu: Remove the unused rcu_irq_exit_preempt() function

rcu: Provide polling interfaces for Tiny RCU grace periods

x86/cpu: Avoid cpuinfo-induced IPIing of idle CPUs

rcu: Remove unused __rcu_is_watching() function

rcu: Support reclaim for head-less object

rcu: Rename *_kfree_callback/*_kfree_rcu_offset/kfree_call_*

rcu: Provide rcu_irq_exit_check_preempt()

rcu: Provide __rcu_is_watching()

rcu: Provide rcu_irq_exit_preempt()

rcu: Rename _kfree_callback/_kfree_rcu_offset/kfree_call_*