diff options
Diffstat (limited to 'Documentation/RCU/stallwarn.rst')
| -rw-r--r-- | Documentation/RCU/stallwarn.rst | 37 |
1 files changed, 23 insertions, 14 deletions
diff --git a/Documentation/RCU/stallwarn.rst b/Documentation/RCU/stallwarn.rst index 28f8ad16db25..e38c587067fc 100644 --- a/Documentation/RCU/stallwarn.rst +++ b/Documentation/RCU/stallwarn.rst @@ -97,12 +97,12 @@ warnings: which will include additional debugging information. - A low-level kernel issue that either fails to invoke one of the - variants of rcu_user_enter(), rcu_user_exit(), rcu_idle_enter(), - rcu_idle_exit(), rcu_irq_enter(), or rcu_irq_exit() on the one + variants of rcu_eqs_enter(true), rcu_eqs_exit(true), ct_idle_enter(), + ct_idle_exit(), ct_irq_enter(), or ct_irq_exit() on the one hand, or that invokes one of them too many times on the other. Historically, the most frequent issue has been an omission of either irq_enter() or irq_exit(), which in turn invoke - rcu_irq_enter() or rcu_irq_exit(), respectively. Building your + ct_irq_enter() or ct_irq_exit(), respectively. Building your kernel with CONFIG_RCU_EQS_DEBUG=y can help track down these types of issues, which sometimes arise in architecture-specific code. @@ -162,6 +162,26 @@ CONFIG_RCU_CPU_STALL_TIMEOUT Stall-warning messages may be enabled and disabled completely via /sys/module/rcupdate/parameters/rcu_cpu_stall_suppress. +CONFIG_RCU_EXP_CPU_STALL_TIMEOUT +-------------------------------- + + Same as the CONFIG_RCU_CPU_STALL_TIMEOUT parameter but only for + the expedited grace period. This parameter defines the period + of time that RCU will wait from the beginning of an expedited + grace period until it issues an RCU CPU stall warning. This time + period is normally 20 milliseconds on Android devices. A zero + value causes the CONFIG_RCU_CPU_STALL_TIMEOUT value to be used, + after conversion to milliseconds. + + This configuration parameter may be changed at runtime via the + /sys/module/rcupdate/parameters/rcu_exp_cpu_stall_timeout, however + this parameter is checked only at the beginning of a cycle. If you + are in a current stall cycle, setting it to a new value will change + the timeout for the -next- stall. + + Stall-warning messages may be enabled and disabled completely via + /sys/module/rcupdate/parameters/rcu_cpu_stall_suppress. + RCU_STALL_DELAY_DELTA --------------------- @@ -254,17 +274,6 @@ period (in this case 2603), the grace-period sequence number (7075), and an estimate of the total number of RCU callbacks queued across all CPUs (625 in this case). -In kernels with CONFIG_RCU_FAST_NO_HZ, more information is printed -for each CPU:: - - 0: (64628 ticks this GP) idle=dd5/3fffffffffffffff/0 softirq=82/543 last_accelerate: a345/d342 dyntick_enabled: 1 - -The "last_accelerate:" prints the low-order 16 bits (in hex) of the -jiffies counter when this CPU last invoked rcu_try_advance_all_cbs() -from rcu_needs_cpu() or last invoked rcu_accelerate_cbs() from -rcu_prepare_for_idle(). "dyntick_enabled: 1" indicates that dyntick-idle -processing is enabled. - If the grace period ends just as the stall warning starts printing, there will be a spurious stall-warning message, which will include the following:: |