# git rev-parse -q --verify 472e5b056f000a778abb41f1e443de58eb259783^{commit} 472e5b056f000a778abb41f1e443de58eb259783 already have revision, skipping fetch # git checkout -q -f -B kisskb 472e5b056f000a778abb41f1e443de58eb259783 # git clean -qxdf # < git log -1 # commit 472e5b056f000a778abb41f1e443de58eb259783 # Author: Linus Torvalds # Date: Thu Oct 1 19:14:36 2020 -0700 # # pipe: remove pipe_wait() and fix wakeup race with splice # # The pipe splice code still used the old model of waiting for pipe IO by # using a non-specific "pipe_wait()" that waited for any pipe event to # happen, which depended on all pipe IO being entirely serialized by the # pipe lock. So by checking the state you were waiting for, and then # adding yourself to the wait queue before dropping the lock, you were # guaranteed to see all the wakeups. # # Strictly speaking, the actual wakeups were not done under the lock, but # the pipe_wait() model still worked, because since the waiter held the # lock when checking whether it should sleep, it would always see the # current state, and the wakeup was always done after updating the state. # # However, commit 0ddad21d3e99 ("pipe: use exclusive waits when reading or # writing") split the single wait-queue into two, and in the process also # made the "wait for event" code wait for _two_ wait queues, and that then # showed a race with the wakers that were not serialized by the pipe lock. # # It's only splice that used that "pipe_wait()" model, so the problem # wasn't obvious, but Josef Bacik reports: # # "I hit a hang with fstest btrfs/187, which does a btrfs send into # /dev/null. This works by creating a pipe, the write side is given to # the kernel to write into, and the read side is handed to a thread that # splices into a file, in this case /dev/null. # # The box that was hung had the write side stuck here [pipe_write] and # the read side stuck here [splice_from_pipe_next -> pipe_wait]. # # [ more details about pipe_wait() scenario ] # # The problem is we're doing the prepare_to_wait, which sets our state # each time, however we can be woken up either with reads or writes. In # the case above we race with the WRITER waking us up, and re-set our # state to INTERRUPTIBLE, and thus never break out of schedule" # # Josef had a patch that avoided the issue in pipe_wait() by just making # it set the state only once, but the deeper problem is that pipe_wait() # depends on a level of synchonization by the pipe mutex that it really # shouldn't. And the whole "wait for any pipe state change" model really # isn't very good to begin with. # # So rather than trying to work around things in pipe_wait(), remove that # legacy model of "wait for arbitrary pipe event" entirely, and actually # create functions that wait for the pipe actually being readable or # writable, and can do so without depending on the pipe lock serializing # everything. # # Fixes: 0ddad21d3e99 ("pipe: use exclusive waits when reading or writing") # Link: https://lore.kernel.org/linux-fsdevel/bfa88b5ad6f069b2b679316b9e495a970130416c.1601567868.git.josef@toxicpanda.com/ # Reported-by: Josef Bacik # Reviewed-and-tested-by: Josef Bacik # Signed-off-by: Linus Torvalds # < /opt/cross/kisskb/br-sparc64-full-2016.08-613-ge98b4dd/bin/sparc64-linux-gcc --version # < /opt/cross/kisskb/br-sparc64-full-2016.08-613-ge98b4dd/bin/sparc64-linux-ld --version # < git log --format=%s --max-count=1 472e5b056f000a778abb41f1e443de58eb259783 # < make -s -j 24 ARCH=sparc O=/kisskb/build/linus_sparc-allmodconfig_sparc64 CROSS_COMPILE=/opt/cross/kisskb/br-sparc64-full-2016.08-613-ge98b4dd/bin/sparc64-linux- allmodconfig # Added to kconfig CONFIG_64BIT=n # Added to kconfig CONFIG_BUILD_DOCSRC=n # Added to kconfig CONFIG_HAVE_FTRACE_MCOUNT_RECORD=n # Added to kconfig CONFIG_SAMPLES=n # Added to kconfig CONFIG_MODULE_SIG=n # < make -s -j 24 ARCH=sparc O=/kisskb/build/linus_sparc-allmodconfig_sparc64 CROSS_COMPILE=/opt/cross/kisskb/br-sparc64-full-2016.08-613-ge98b4dd/bin/sparc64-linux- help # make -s -j 24 ARCH=sparc O=/kisskb/build/linus_sparc-allmodconfig_sparc64 CROSS_COMPILE=/opt/cross/kisskb/br-sparc64-full-2016.08-613-ge98b4dd/bin/sparc64-linux- olddefconfig # make -s -j 24 ARCH=sparc O=/kisskb/build/linus_sparc-allmodconfig_sparc64 CROSS_COMPILE=/opt/cross/kisskb/br-sparc64-full-2016.08-613-ge98b4dd/bin/sparc64-linux- :1511:2: warning: #warning syscall clone3 not implemented [-Wcpp] In file included from /kisskb/src/arch/sparc/include/asm/cmpxchg.h:7:0, from /kisskb/src/arch/sparc/include/asm/atomic_32.h:17, from /kisskb/src/arch/sparc/include/asm/atomic.h:7, from /kisskb/src/include/linux/atomic.h:7, from /kisskb/src/include/linux/page_counter.h:5, from /kisskb/src/mm/memcontrol.c:25: /kisskb/src/mm/memcontrol.c: In function 'memcg_reparent_objcgs': /kisskb/src/arch/sparc/include/asm/cmpxchg_32.h:28:22: warning: value computed is not used [-Wunused-value] #define xchg(ptr,x) ((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr)))) ^ /kisskb/src/mm/memcontrol.c:333:2: note: in expansion of macro 'xchg' xchg(&objcg->memcg, parent); ^ /kisskb/src/arch/sparc/include/asm/cmpxchg_32.h:28:22: warning: value computed is not used [-Wunused-value] #define xchg(ptr,x) ((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr)))) ^ /kisskb/src/mm/memcontrol.c:340:3: note: in expansion of macro 'xchg' xchg(&iter->memcg, parent); ^ /kisskb/src/drivers/tty/serial/sunzilog.c:1128:13: warning: 'sunzilog_putchar' defined but not used [-Wunused-function] static void sunzilog_putchar(struct uart_port *port, int ch) ^ /kisskb/src/drivers/input/joystick/analog.c:160:2: warning: #warning Precise timer not defined for this architecture. [-Wcpp] #warning Precise timer not defined for this architecture. ^ In file included from /kisskb/src/arch/sparc/include/asm/cmpxchg.h:7:0, from /kisskb/src/arch/sparc/include/asm/atomic_32.h:17, from /kisskb/src/arch/sparc/include/asm/atomic.h:7, from /kisskb/src/include/linux/atomic.h:7, from /kisskb/src/include/asm-generic/bitops/lock.h:5, from /kisskb/src/arch/sparc/include/asm/bitops_32.h:102, from /kisskb/src/arch/sparc/include/asm/bitops.h:7, from /kisskb/src/include/linux/bitops.h:29, from /kisskb/src/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c:11: /kisskb/src/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c: In function 'ixgbevf_xdp_setup': /kisskb/src/arch/sparc/include/asm/cmpxchg_32.h:28:22: warning: value computed is not used [-Wunused-value] #define xchg(ptr,x) ((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr)))) ^ /kisskb/src/drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c:4469:4: note: in expansion of macro 'xchg' xchg(&adapter->rx_ring[i]->xdp_prog, adapter->xdp_prog); ^ In file included from /kisskb/src/drivers/net/ethernet/intel/ice/ice_flex_pipe.c:6:0: /kisskb/src/drivers/net/ethernet/intel/ice/ice_flex_pipe.c: In function 'ice_free_flow_profs': /kisskb/src/drivers/net/ethernet/intel/ice/ice_flow.h:197:33: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] #define ICE_FLOW_ENTRY_HNDL(e) ((u64)e) ^ /kisskb/src/drivers/net/ethernet/intel/ice/ice_flex_pipe.c:2921:9: note: in expansion of macro 'ICE_FLOW_ENTRY_HNDL' ICE_FLOW_ENTRY_HNDL(e)); ^ In file included from /kisskb/src/drivers/net/ethernet/intel/ice/ice_flow.c:5:0: /kisskb/src/drivers/net/ethernet/intel/ice/ice_flow.c: In function 'ice_flow_add_entry': /kisskb/src/drivers/net/ethernet/intel/ice/ice_flow.h:197:33: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] #define ICE_FLOW_ENTRY_HNDL(e) ((u64)e) ^ /kisskb/src/drivers/net/ethernet/intel/ice/ice_flow.c:946:13: note: in expansion of macro 'ICE_FLOW_ENTRY_HNDL' *entry_h = ICE_FLOW_ENTRY_HNDL(e); ^ /kisskb/src/drivers/net/ethernet/intel/ice/ice_flow.c: In function 'ice_flow_rem_entry': /kisskb/src/drivers/net/ethernet/intel/ice/ice_flow.h:198:32: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast] #define ICE_FLOW_ENTRY_PTR(h) ((struct ice_flow_entry *)(h)) ^ /kisskb/src/drivers/net/ethernet/intel/ice/ice_flow.c:974:10: note: in expansion of macro 'ICE_FLOW_ENTRY_PTR' entry = ICE_FLOW_ENTRY_PTR(entry_h); ^ In file included from /kisskb/src/arch/sparc/include/asm/cmpxchg.h:7:0, from /kisskb/src/arch/sparc/include/asm/atomic_32.h:17, from /kisskb/src/arch/sparc/include/asm/atomic.h:7, from /kisskb/src/include/linux/atomic.h:7, from /kisskb/src/include/asm-generic/bitops/lock.h:5, from /kisskb/src/arch/sparc/include/asm/bitops_32.h:102, from /kisskb/src/arch/sparc/include/asm/bitops.h:7, from /kisskb/src/include/linux/bitops.h:29, from /kisskb/src/include/linux/kernel.h:12, from /kisskb/src/include/linux/list.h:9, from /kisskb/src/include/linux/wait.h:7, from /kisskb/src/include/linux/wait_bit.h:8, from /kisskb/src/include/linux/fs.h:6, from /kisskb/src/fs/ocfs2/file.c:13: /kisskb/src/fs/ocfs2/file.c: In function 'ocfs2_file_write_iter': /kisskb/src/arch/sparc/include/asm/cmpxchg_32.h:28:22: warning: value computed is not used [-Wunused-value] #define xchg(ptr,x) ((__typeof__(*(ptr)))__xchg((unsigned long)(x),(ptr),sizeof(*(ptr)))) ^ /kisskb/src/fs/ocfs2/file.c:2419:3: note: in expansion of macro 'xchg' xchg(&iocb->ki_complete, saved_ki_complete); ^ In file included from /kisskb/src/include/linux/printk.h:405:0, from /kisskb/src/include/linux/kernel.h:15, from /kisskb/src/include/linux/clk.h:13, from /kisskb/src/drivers/crypto/sa2ul.c:11: /kisskb/src/drivers/crypto/sa2ul.c: In function 'sa_sha_init': /kisskb/src/drivers/crypto/sa2ul.c:1486:33: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast] crypto_ahash_digestsize(tfm), (u64)rctx); ^ /kisskb/src/include/linux/dynamic_debug.h:129:15: note: in definition of macro '__dynamic_func_call' func(&id, ##__VA_ARGS__); \ ^ /kisskb/src/include/linux/dynamic_debug.h:161:2: note: in expansion of macro '_dynamic_func_call' _dynamic_func_call(fmt,__dynamic_dev_dbg, \ ^ /kisskb/src/include/linux/dev_printk.h:115:2: note: in expansion of macro 'dynamic_dev_dbg' dynamic_dev_dbg(dev, dev_fmt(fmt), ##__VA_ARGS__) ^ /kisskb/src/drivers/crypto/sa2ul.c:1485:2: note: in expansion of macro 'dev_dbg' dev_dbg(sa_k3_dev, "init: digest size: %d, rctx=%llx\n", ^ /kisskb/src/drivers/staging/media/tegra-vde/vde.c:916:12: warning: 'tegra_vde_runtime_suspend' defined but not used [-Wunused-function] static int tegra_vde_runtime_suspend(struct device *dev) ^ WARNING: modpost: EXPORT symbol "bzero_1page" [vmlinux] version generation failed, symbol will not be versioned. WARNING: modpost: EXPORT symbol "___rw_read_exit" [vmlinux] version generation failed, symbol will not be versioned. WARNING: modpost: EXPORT symbol "___rw_read_try" [vmlinux] version generation failed, symbol will not be versioned. WARNING: modpost: EXPORT symbol "__ndelay" [vmlinux] version generation failed, symbol will not be versioned. WARNING: modpost: EXPORT symbol "__ashrdi3" [vmlinux] version generation failed, symbol will not be versioned. WARNING: modpost: EXPORT symbol "empty_zero_page" [vmlinux] version generation failed, symbol will not be versioned. WARNING: modpost: EXPORT symbol "__udelay" [vmlinux] version generation failed, symbol will not be versioned. WARNING: modpost: EXPORT symbol "__lshrdi3" [vmlinux] version generation failed, symbol will not be versioned. WARNING: modpost: EXPORT symbol "___rw_write_enter" [vmlinux] version generation failed, symbol will not be versioned. WARNING: modpost: EXPORT symbol "__ashldi3" [vmlinux] version generation failed, symbol will not be versioned. WARNING: modpost: EXPORT symbol "__copy_1page" [vmlinux] version generation failed, symbol will not be versioned. WARNING: modpost: EXPORT symbol "__muldi3" [vmlinux] version generation failed, symbol will not be versioned. WARNING: modpost: EXPORT symbol "__divdi3" [vmlinux] version generation failed, symbol will not be versioned. WARNING: modpost: EXPORT symbol "___rw_read_enter" [vmlinux] version generation failed, symbol will not be versioned. arch/sparc/kernel/head_32.o: In function `current_pc': arch/sparc/kernel/head_32.o:(.head.text+0x5040): relocation truncated to fit: R_SPARC_WDISP22 against `.init.text' arch/sparc/kernel/head_32.o: In function `halt_notsup': arch/sparc/kernel/head_32.o:(.head.text+0x5100): relocation truncated to fit: R_SPARC_WDISP22 against `.init.text' arch/sparc/kernel/head_32.o: In function `leon_init': arch/sparc/kernel/head_32.o:(.init.text+0xa4): relocation truncated to fit: R_SPARC_WDISP22 against symbol `leon_smp_cpu_startup' defined in .text section in arch/sparc/kernel/trampoline_32.o arch/sparc/kernel/process_32.o:(.fixup+0x4): relocation truncated to fit: R_SPARC_WDISP22 against `.text' arch/sparc/kernel/process_32.o:(.fixup+0xc): relocation truncated to fit: R_SPARC_WDISP22 against `.text' arch/sparc/kernel/signal_32.o:(.fixup+0x4): relocation truncated to fit: R_SPARC_WDISP22 against `.text' arch/sparc/kernel/signal_32.o:(.fixup+0x10): relocation truncated to fit: R_SPARC_WDISP22 against `.text' arch/sparc/kernel/signal_32.o:(.fixup+0x1c): relocation truncated to fit: R_SPARC_WDISP22 against `.text' arch/sparc/kernel/signal_32.o:(.fixup+0x28): relocation truncated to fit: R_SPARC_WDISP22 against `.text' arch/sparc/kernel/signal_32.o:(.fixup+0x34): relocation truncated to fit: R_SPARC_WDISP22 against `.text' arch/sparc/kernel/signal_32.o:(.fixup+0x40): additional relocation overflows omitted from the output make[1]: *** [/kisskb/src/Makefile:1162: vmlinux] Error 1 make: *** [Makefile:185: __sub-make] Error 2 Command 'make -s -j 24 ARCH=sparc O=/kisskb/build/linus_sparc-allmodconfig_sparc64 CROSS_COMPILE=/opt/cross/kisskb/br-sparc64-full-2016.08-613-ge98b4dd/bin/sparc64-linux- ' returned non-zero exit status 2 # rm -rf /kisskb/build/linus_sparc-allmodconfig_sparc64 # Build took: 0:15:05.307745